Repository: jpbetz/kubernetes
Pull request #124: feat: add declarative_validation_mismatch_total metric and associated declarative validation runtime verification tests
Author: login: aaron-prindle
Created: 2025-03-07T04:49:47Z | Merged: 2025-03-10T22:32:05Z

This PR adds the declarative_validation_mismatch_total metric as well as runtime verification testing to validation-gen



Diff:
diff --git a/pkg/registry/core/replicationcontroller/strategy.go b/pkg/registry/core/replicationcontroller/strategy.go
index 0e64d3f4514f7..5f42f58851634 100644
--- a/pkg/registry/core/replicationcontroller/strategy.go
+++ b/pkg/registry/core/replicationcontroller/strategy.go
@@ -125,14 +125,27 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
-		if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		// Determine if takeover is enabled
+		takeover := utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover)
+
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.ValidateDeclarativelyWithRecovery(ctx, nil, legacyscheme.Scheme, obj, takeover)
+
+		// Compare imperative and declarative errors and log + emit metric if there's a mismatch
+		rest.CompareDeclarativeErrorsAndEmitMismatches(allErrs, declarativeErrs, takeover)
+
+		// Only apply declarative errors if takeover is enabled
+		if takeover {
 			allErrs = append(allErrs.RemoveCoveredByDeclarative(), declarativeErrs...)
 		}
-		// TODO: emit mismatch_metric by comparing between allErrs.ExtractCoveredByDeclarative() and declarativeErrs
 	}
+
 	return allErrs
 }
 
@@ -184,14 +197,24 @@ func (rcStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) f
 		}
 	}
 
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		// Following above pattern, we need to validate both create and update.
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
-		declarativeErrs = append(declarativeErrs, rest.ValidateUpdateDeclaratively(ctx, nil, legacyscheme.Scheme, obj, old)...)
-		if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		// Determine if takeover is enabled
+		takeover := utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover)
+
+		// Run both validations with panic recovery
+		declarativeErrs := rest.ValidateDeclarativelyWithRecovery(ctx, nil, legacyscheme.Scheme, obj, takeover)
+		declarativeErrs = append(
+			declarativeErrs,
+			rest.ValidateUpdateDeclarativelyWithRecovery(ctx, nil, legacyscheme.Scheme, obj, old, takeover)...)
+
+		// Only apply declarative errors if takeover is enabled
+		if takeover {
 			errs = append(errs.RemoveCoveredByDeclarative(), declarativeErrs...)
 		}
-		// TODO: emit mismatch_metric by comparing between errs.ExtractCoveredByDeclarative() and declarativeErrs
+
+		// Compare imperative and declarative errors and emit metric if there's a mismatch
+		rest.CompareDeclarativeErrorsAndEmitMismatches(errs, declarativeErrs, takeover)
 	}
 
 	return errs
diff --git a/staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go b/staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
index 1fa6dc1f55231..5942d5d41bec4 100644
--- a/staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
+++ b/staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
@@ -25,7 +25,10 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/validation/field"
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
 	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
+	validationmetrics "k8s.io/apiserver/pkg/validation"
+	"k8s.io/klog/v2"
 )
 
 // ValidateDeclaratively validates obj against declarative validation tags
@@ -106,3 +109,210 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	// Dedupe imperative errors of exact error matches as they are
+	// not intended and come from (buggy) duplicate validation calls
+	// This is necessary as without deduping we could get unmatched
+	// imperative errors for cases that are correct (matching)
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors.
+	// We use a fuzzy matching approach to find corresponding declarative errors
+	// for each imperative error marked as CoveredByDeclarative.
+	// As matches are found, they're removed from the 'remaining' list.
+	// They are removed from `remaining` with a "1:many" mapping: for a given
+	// imperative error we mark as matched all matching declarative errors
+	// This allows us to:
+	// 1. Detect imperative errors that should have matching declarative errors but don't
+	// 2. Identify extra declarative errors with no imperative counterpart
+	// Both cases indicate issues with the declarative validation implementation.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		tmp := make(field.ErrorList, 0, len(remaining))
+		matchCount := 0
+
+		for _, dErr := range remaining {
+			if fuzzyMatcher.Matches(iErr, dErr) {
+				matchCount++
+			} else {
+				tmp = append(tmp, dErr)
+			}
+		}
+
+		if matchCount == 0 {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					fuzzyMatcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+
+		remaining = tmp
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra"
+	for _, dErr := range remaining {
+		mismatchDetails = append(mismatchDetails,
+			fmt.Sprintf(
+				"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+					"This may indicate an issue with declarative validation. %s",
+				fuzzyMatcher.Render(dErr),
+				recommendation,
+			),
+		)
+	}
+
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment the panic metric and either log or append errors based on the takeover parameter.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList, takeover bool) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if takeover {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// withRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func withRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+	takeover bool,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs, takeover)()
+
+		return validateFunc(ctx, options, scheme, obj)
+	}
+}
+
+// withRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func withRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+	takeover bool,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs, takeover)()
+
+		return validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+	}
+}
+
+// ValidateDeclarativelyWithRecovery validates obj against declarative validation tags
+// with panic recovery logic. It uses the API version extracted from ctx and the
+// provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// takeover determines if panic recovery should return validation errors (true) or
+// just log warnings (false).
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// takeover is true.
+func ValidateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object, takeover bool) field.ErrorList {
+	return withRecover(ValidateDeclaratively, takeover)(ctx, options, scheme, obj)
+}
+
+// ValidateUpdateDeclarativelyWithRecovery validates obj and oldObj against declarative
+// validation tags with panic recovery logic. It uses the API version extracted from
+// ctx and the provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// takeover determines if panic recovery should return validation errors (true) or
+// just log warnings (false).
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// takeover is true.
+func ValidateUpdateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object, takeover bool) field.ErrorList {
+	return withRecoverUpdate(ValidateUpdateDeclaratively, takeover)(ctx, options, scheme, obj, oldObj)
+}
diff --git a/staging/src/k8s.io/apiserver/pkg/registry/rest/validate_test.go b/staging/src/k8s.io/apiserver/pkg/registry/rest/validate_test.go
index 8ed9ed9adee91..26952f27a1490 100644
--- a/staging/src/k8s.io/apiserver/pkg/registry/rest/validate_test.go
+++ b/staging/src/k8s.io/apiserver/pkg/registry/rest/validate_test.go
@@ -17,8 +17,13 @@ limitations under the License.
 package rest
 
 import (
+	"bytes"
 	"context"
+	"flag"
 	"fmt"
+	"reflect"
+	"regexp"
+	"strings"
 	"testing"
 
 	v1 "k8s.io/api/core/v1"
@@ -31,6 +36,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	fieldtesting "k8s.io/apimachinery/pkg/util/validation/field/testing"
 	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
+	"k8s.io/klog/v2"
 )
 
 func TestValidateDeclaratively(t *testing.T) {
@@ -182,3 +188,437 @@ func (p Pod) DeepCopyObject() runtime.Object {
 		RestartPolicy: p.RestartPolicy,
 	}
 }
+
+// TestCheckDeclarativeValidationMismatches tests all scenarios for
+// the gatherDeclarativeValidationMismatches function
+func TestGatherDeclarativeValidationMismatches(t *testing.T) {
+	replicasPath := field.NewPath("spec").Child("replicas")
+	minReadySecondsPath := field.NewPath("spec").Child("minReadySeconds")
+	selectorPath := field.NewPath("spec").Child("selector")
+
+	errA := field.Invalid(replicasPath, nil, "regular error A")
+	errB := field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum")
+	coveredErrB := field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum")
+	errBWithDiffDetail := field.Invalid(minReadySecondsPath, -1, "covered error B - different detail").WithOrigin("minimum")
+	coveredErrB.CoveredByDeclarative = true
+	errC := field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum")
+	coveredErrC := field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum")
+	coveredErrC.CoveredByDeclarative = true
+	errCWithDiffOrigin := field.Invalid(replicasPath, nil, "covered error C").WithOrigin("maximum")
+	errD := field.Invalid(selectorPath, nil, "regular error D")
+
+	tests := []struct {
+		name                    string
+		imperativeErrors        field.ErrorList
+		declarativeErrors       field.ErrorList
+		takeover                bool
+		expectMismatches        bool
+		expectDetailsContaining []string
+	}{
+		{
+			name:                    "Declarative and imperative return 0 errors - no mismatch",
+			imperativeErrors:        field.ErrorList{},
+			declarativeErrors:       field.ErrorList{},
+			takeover:                false,
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Declarative returns multiple errors with different origins, errors match - no mismatch",
+			imperativeErrors: field.ErrorList{
+				errA,
+				coveredErrB,
+				coveredErrC,
+				errD,
+			},
+			declarativeErrors: field.ErrorList{
+				errB,
+				errC,
+			},
+			takeover:                false,
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Declarative returns multiple errors with different origins, errors don't match - mismatch case",
+			imperativeErrors: field.ErrorList{
+				errA,
+				coveredErrB,
+				coveredErrC,
+			},
+			declarativeErrors: field.ErrorList{
+				errB,
+				errCWithDiffOrigin,
+			},
+			takeover:         true,
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"extra error(s) found",
+				"replicas",
+				"Consider disabling the DeclarativeValidationTakeover feature gate",
+			},
+		},
+		{
+			name: "Declarative and imperative return exactly 1 error, errors match - no mismatch",
+			imperativeErrors: field.ErrorList{
+				coveredErrB,
+			},
+			declarativeErrors: field.ErrorList{
+				errB,
+			},
+			takeover:                false,
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Declarative and imperative exactly 1 error, errors don't match - mismatch",
+			imperativeErrors: field.ErrorList{
+				coveredErrB,
+			},
+			declarativeErrors: field.ErrorList{
+				errC,
+			},
+			takeover:         false,
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"minReadySeconds",
+				"extra error(s) found",
+				"replicas",
+				"This difference should not affect system operation since hand written validation is authoritative",
+			},
+		},
+		{
+			name: "Declarative returns 0 errors, imperative returns 1 covered error - mismatch",
+			imperativeErrors: field.ErrorList{
+				coveredErrB,
+			},
+			declarativeErrors: field.ErrorList{},
+			takeover:          true,
+			expectMismatches:  true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"minReadySeconds",
+				"Consider disabling the DeclarativeValidationTakeover feature gate",
+			},
+		},
+		{
+			name: "Declarative returns 0 errors, imperative returns 1 uncovered error - no mismatch",
+			imperativeErrors: field.ErrorList{
+				errB,
+			},
+			declarativeErrors:       field.ErrorList{},
+			takeover:                false,
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name:             "Declarative returns 1 error, imperative returns 0 error - mismatch",
+			imperativeErrors: field.ErrorList{},
+			declarativeErrors: field.ErrorList{
+				errB,
+			},
+			takeover:         false,
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"extra error(s) found",
+				"minReadySeconds",
+				"This difference should not affect system operation since hand written validation is authoritative",
+			},
+		},
+		{
+			name: "Declarative returns 1 error, imperative returns 3 matching errors  - no mismatch",
+			imperativeErrors: field.ErrorList{
+				coveredErrB,
+			},
+			declarativeErrors: field.ErrorList{
+				errB,
+				errB,
+				errBWithDiffDetail,
+			},
+			takeover:                false,
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			details := gatherDeclarativeValidationMismatches(tt.imperativeErrors, tt.declarativeErrors, tt.takeover)
+			// Check if mismatches were found if expected
+			if tt.expectMismatches && len(details) == 0 {
+				t.Errorf("Expected mismatches but got none")
+			}
+			// Check if details contain expected text
+			detailsStr := strings.Join(details, " ")
+			for _, expectedContent := range tt.expectDetailsContaining {
+				if !strings.Contains(detailsStr, expectedContent) {
+					t.Errorf("Expected details to contain: %q, but they didn't.\nDetails were:\n%s",
+						expectedContent, strings.Join(details, "\n"))
+				}
+			}
+			// If we don't expect any details, make sure none provided
+			if len(tt.expectDetailsContaining) == 0 && len(details) > 0 {
+				t.Errorf("Expected no details, but got %d details: %v", len(details), details)
+			}
+		})
+	}
+}
+
+func TestWithRecover(t *testing.T) {
+	ctx := context.Background()
+	scheme := runtime.NewScheme()
+	options := sets.New[string]()
+	obj := &runtime.Unknown{}
+
+	tests := []struct {
+		name            string
+		validateFn      func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object) field.ErrorList
+		takeoverEnabled bool
+		wantErrs        field.ErrorList
+		expectLogRegex  string
+	}{
+		{
+			name: "no panic",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object) field.ErrorList {
+				return field.ErrorList{
+					field.Invalid(field.NewPath("field"), "value", "reason"),
+				}
+			},
+			takeoverEnabled: false,
+			wantErrs: field.ErrorList{
+				field.Invalid(field.NewPath("field"), "value", "reason"),
+			},
+			expectLogRegex: "",
+		},
+		{
+			name: "panic with takeover disabled",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object) field.ErrorList {
+				panic("test panic")
+			},
+			takeoverEnabled: false,
+			wantErrs:        nil,
+			// logs have a prefix of the form - W0309 21:05:33.865030 1926106 validate.go:199]
+			expectLogRegex: "W.*panic during declarative validation: test panic",
+		},
+		{
+			name: "panic with takeover enabled",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object) field.ErrorList {
+				panic("test panic")
+			},
+			takeoverEnabled: true,
+			wantErrs: field.ErrorList{
+				field.InternalError(nil, fmt.Errorf("panic during declarative validation: test panic")),
+			},
+			expectLogRegex: "",
+		},
+		{
+			name: "nil return, no panic",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object) field.ErrorList {
+				return nil // no errors, no panic
+			},
+			takeoverEnabled: false,
+			wantErrs:        nil,
+			expectLogRegex:  "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			flag.Set("v", "6")
+			flag.Parse()
+			klog.SetOutput(&buf)
+			klog.LogToStderr(false)
+			defer klog.LogToStderr(true)
+
+			// Pass the takeover flag to withRecover instead of relying on the feature gate
+			wrapped := withRecover(tt.validateFn, tt.takeoverEnabled)
+			gotErrs := wrapped(ctx, options, scheme, obj)
+
+			klog.Flush()
+			logOutput := buf.String()
+
+			// Compare gotErrs vs. tt.wantErrs
+			if !equalErrorLists(gotErrs, tt.wantErrs) {
+				t.Errorf("withRecover() gotErrs = %#v, want %#v", gotErrs, tt.wantErrs)
+			}
+
+			// Check logs if needed
+			if tt.expectLogRegex != "" {
+				matched, err := regexp.MatchString(tt.expectLogRegex, logOutput)
+				if err != nil {
+					t.Fatalf("Bad regex: %v", err)
+				}
+				if !matched {
+					t.Errorf("Expected log output %q, but got:\n%s", tt.expectLogRegex, logOutput)
+				}
+			} else if strings.Contains(logOutput, "panic during declarative validation") {
+				t.Errorf("Unexpected panic log found: %s", logOutput)
+			}
+		})
+	}
+}
+
+func TestWithRecoverUpdate(t *testing.T) {
+	ctx := context.Background()
+	scheme := runtime.NewScheme()
+	options := sets.New[string]()
+	obj := &runtime.Unknown{}
+	oldObj := &runtime.Unknown{}
+
+	tests := []struct {
+		name            string
+		validateFn      func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object, runtime.Object) field.ErrorList
+		takeoverEnabled bool
+		wantErrs        field.ErrorList
+		expectLogRegex  string
+	}{
+		{
+			name: "no panic",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object, runtime.Object) field.ErrorList {
+				return field.ErrorList{
+					field.Invalid(field.NewPath("field"), "value", "reason"),
+				}
+			},
+			takeoverEnabled: false,
+			wantErrs: field.ErrorList{
+				field.Invalid(field.NewPath("field"), "value", "reason"),
+			},
+			expectLogRegex: "",
+		},
+		{
+			name: "panic with takeover disabled",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object, runtime.Object) field.ErrorList {
+				panic("test update panic")
+			},
+			takeoverEnabled: false,
+			wantErrs:        nil,
+			// logs have a prefix of the form - W0309 21:05:33.865030 1926106 validate.go:199]
+			expectLogRegex: "W.*panic during declarative validation: test update panic",
+		},
+		{
+			name: "panic with takeover enabled",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object, runtime.Object) field.ErrorList {
+				panic("test update panic")
+			},
+			takeoverEnabled: true,
+			wantErrs: field.ErrorList{
+				field.InternalError(nil, fmt.Errorf("panic during declarative validation: test update panic")),
+			},
+			expectLogRegex: "",
+		},
+		{
+			name: "nil return, no panic",
+			validateFn: func(context.Context, sets.Set[string], *runtime.Scheme, runtime.Object, runtime.Object) field.ErrorList {
+				return nil
+			},
+			takeoverEnabled: false,
+			wantErrs:        nil,
+			expectLogRegex:  "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			flag.Set("v", "6")
+			flag.Parse()
+			klog.SetOutput(&buf)
+			klog.LogToStderr(false)
+			defer klog.LogToStderr(true)
+
+			// Pass the takeover flag to withRecoverUpdate instead of relying on the feature gate
+			wrapped := withRecoverUpdate(tt.validateFn, tt.takeoverEnabled)
+			gotErrs := wrapped(ctx, options, scheme, obj, oldObj)
+
+			klog.Flush()
+			logOutput := buf.String()
+
+			// Compare gotErrs with wantErrs
+			if !equalErrorLists(gotErrs, tt.wantErrs) {
+				t.Errorf("withRecoverUpdate() gotErrs = %#v, want %#v", gotErrs, tt.wantErrs)
+			}
+
+			// Verify log output
+			if tt.expectLogRegex != "" {
+				matched, err := regexp.MatchString(tt.expectLogRegex, logOutput)
+				if err != nil {
+					t.Fatalf("Bad regex: %v", err)
+				}
+				if !matched {
+					t.Errorf("Expected log pattern %q, but got:\n%s", tt.expectLogRegex, logOutput)
+				}
+			} else if strings.Contains(logOutput, "panic during declarative validation") {
+				t.Errorf("Unexpected panic log found: %s", logOutput)
+			}
+		})
+	}
+}
+
+func TestValidateDeclarativelyWithRecovery(t *testing.T) {
+	ctx := context.Background()
+	scheme := runtime.NewScheme()
+	options := sets.New[string]()
+	obj := &runtime.Unknown{}
+
+	// Simple test for the ValidateDeclarativelyWithRecovery function
+	t.Run("with takeover disabled", func(t *testing.T) {
+		errs := ValidateDeclarativelyWithRecovery(ctx, options, scheme, obj, false)
+		if errs == nil {
+			// This is expected to error since the request info is missing
+			t.Errorf("Expected errors but got nil")
+		}
+	})
+
+	t.Run("with takeover enabled", func(t *testing.T) {
+		errs := ValidateDeclarativelyWithRecovery(ctx, options, scheme, obj, true)
+		if errs == nil {
+			// This is expected to error since the request info is missing
+			t.Errorf("Expected errors but got nil")
+		}
+	})
+}
+
+func TestValidateUpdateDeclarativelyWithRecovery(t *testing.T) {
+	ctx := context.Background()
+	scheme := runtime.NewScheme()
+	options := sets.New[string]()
+	obj := &runtime.Unknown{}
+	oldObj := &runtime.Unknown{}
+
+	// Simple test for the ValidateUpdateDeclarativelyWithRecovery function
+	t.Run("with takeover disabled", func(t *testing.T) {
+		errs := ValidateUpdateDeclarativelyWithRecovery(ctx, options, scheme, obj, oldObj, false)
+		if errs == nil {
+			// This is expected to error since the request info is missing
+			t.Errorf("Expected errors but got nil")
+		}
+	})
+
+	t.Run("with takeover enabled", func(t *testing.T) {
+		errs := ValidateUpdateDeclarativelyWithRecovery(ctx, options, scheme, obj, oldObj, true)
+		if errs == nil {
+			// This is expected to error since the request info is missing
+			t.Errorf("Expected errors but got nil")
+		}
+	})
+}
+
+func equalErrorLists(a, b field.ErrorList) bool {
+	// If both are nil, consider them equal
+	if a == nil && b == nil {
+		return true
+	}
+	// If one is nil and the other not, they're different
+	if (a == nil && b != nil) || (a != nil && b == nil) {
+		return false
+	}
+	// Both non-nil: do a normal DeepEqual
+	return reflect.DeepEqual(a, b)
+}
diff --git a/staging/src/k8s.io/apiserver/pkg/validation/metrics.go b/staging/src/k8s.io/apiserver/pkg/validation/metrics.go
new file mode 100644
index 0000000000000..e3f00c129da35
--- /dev/null
+++ b/staging/src/k8s.io/apiserver/pkg/validation/metrics.go
@@ -0,0 +1,90 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
+)
+
+const (
+	namespace = "apiserver" // Keep it consistent; apiserver is handling it
+	subsystem = "validation"
+)
+
+// Separate counter options variable for reuse during reset.
+var declarativeValidationMismatchCounterOpts = &metrics.CounterOpts{
+	Namespace:      namespace,
+	Subsystem:      subsystem,
+	Name:           "declarative_validation_mismatch_total",
+	Help:           "Number of times declarative validation results differed from handwritten validation results for core types.",
+	StabilityLevel: metrics.BETA,
+}
+
+// Counter options for declarative validation panics
+var declarativeValidationPanicCounterOpts = &metrics.CounterOpts{
+	Namespace:      namespace,
+	Subsystem:      subsystem,
+	Name:           "declarative_validation_panic_total",
+	Help:           "Number of times declarative validation has panicked during validation.",
+	StabilityLevel: metrics.BETA,
+}
+
+// ValidationMetrics is the interface for validation metrics.
+type ValidationMetrics interface {
+	EmitDeclarativeValidationMismatchMetric()
+	EmitDeclarativeValidationPanicMetric()
+	Reset()
+}
+
+var validationMetricsInstance = &validationMetrics{
+	DeclarativeValidationMismatchCounter: metrics.NewCounter(declarativeValidationMismatchCounterOpts),
+	DeclarativeValidationPanicCounter:    metrics.NewCounter(declarativeValidationPanicCounterOpts),
+}
+
+// Metrics provides access to validation metrics.
+var Metrics ValidationMetrics = validationMetricsInstance
+
+func init() {
+	legacyregistry.MustRegister(validationMetricsInstance.DeclarativeValidationMismatchCounter)
+	legacyregistry.MustRegister(validationMetricsInstance.DeclarativeValidationPanicCounter)
+}
+
+type validationMetrics struct {
+	DeclarativeValidationMismatchCounter *metrics.Counter
+	DeclarativeValidationPanicCounter    *metrics.Counter
+}
+
+// Reset resets the validation metrics.
+func (m *validationMetrics) Reset() {
+	m.DeclarativeValidationMismatchCounter = metrics.NewCounter(declarativeValidationMismatchCounterOpts)
+	m.DeclarativeValidationPanicCounter = metrics.NewCounter(declarativeValidationPanicCounterOpts)
+}
+
+// EmitDeclarativeValidationMismatchMetric increments the counter for the declarative_validation_mismatch_total metric.
+func (m *validationMetrics) EmitDeclarativeValidationMismatchMetric() {
+	m.DeclarativeValidationMismatchCounter.Inc()
+}
+
+// EmitDeclarativeValidationPanicMetric increments the counter for the declarative_validation_panic_total metric.
+func (m *validationMetrics) EmitDeclarativeValidationPanicMetric() {
+	m.DeclarativeValidationPanicCounter.Inc()
+}
+
+func ResetValidationMetricsInstance() {
+	validationMetricsInstance.Reset()
+}
diff --git a/staging/src/k8s.io/apiserver/pkg/validation/metrics_test.go b/staging/src/k8s.io/apiserver/pkg/validation/metrics_test.go
new file mode 100644
index 0000000000000..5d9fd521b970a
--- /dev/null
+++ b/staging/src/k8s.io/apiserver/pkg/validation/metrics_test.go
@@ -0,0 +1,150 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"strings"
+	"testing"
+
+	"k8s.io/component-base/metrics/legacyregistry"
+	"k8s.io/component-base/metrics/testutil"
+)
+
+// TestDeclarativeValidationMismatchMetric tests that the mismatch metric correctly increments once
+func TestDeclarativeValidationMismatchMetric(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetValidationMetricsInstance()
+
+	// Increment the metric once
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+
+	expected := `
+	# HELP apiserver_validation_declarative_validation_mismatch_total [BETA] Number of times declarative validation results differed from handwritten validation results for core types.
+	# TYPE apiserver_validation_declarative_validation_mismatch_total counter
+	apiserver_validation_declarative_validation_mismatch_total 1
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_mismatch_total"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestDeclarativeValidationPanicMetric tests that the panic metric correctly increments once
+func TestDeclarativeValidationPanicMetric(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetValidationMetricsInstance()
+
+	// Increment the metric once
+	Metrics.EmitDeclarativeValidationPanicMetric()
+
+	expected := `
+	# HELP apiserver_validation_declarative_validation_panic_total [BETA] Number of times declarative validation has panicked during validation.
+	# TYPE apiserver_validation_declarative_validation_panic_total counter
+	apiserver_validation_declarative_validation_panic_total 1
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_panic_total"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestDeclarativeValidationMismatchMetricMultiple tests that the mismatch metric correctly increments multiple times
+func TestDeclarativeValidationMismatchMetricMultiple(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetValidationMetricsInstance()
+
+	// Increment the metric three times
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+
+	expected := `
+	# HELP apiserver_validation_declarative_validation_mismatch_total [BETA] Number of times declarative validation results differed from handwritten validation results for core types.
+	# TYPE apiserver_validation_declarative_validation_mismatch_total counter
+	apiserver_validation_declarative_validation_mismatch_total 3
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_mismatch_total"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestDeclarativeValidationPanicMetricMultiple tests that the panic metric correctly increments multiple times
+func TestDeclarativeValidationPanicMetricMultiple(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetValidationMetricsInstance()
+
+	// Increment the metric three times
+	Metrics.EmitDeclarativeValidationPanicMetric()
+	Metrics.EmitDeclarativeValidationPanicMetric()
+	Metrics.EmitDeclarativeValidationPanicMetric()
+
+	expected := `
+	# HELP apiserver_validation_declarative_validation_panic_total [BETA] Number of times declarative validation has panicked during validation.
+	# TYPE apiserver_validation_declarative_validation_panic_total counter
+	apiserver_validation_declarative_validation_panic_total 3
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_panic_total"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestDeclarativeValidationMetricsReset tests that the Reset function correctly resets the metrics to zero
+func TestDeclarativeValidationMetricsReset(t *testing.T) {
+	defer legacyregistry.Reset()
+	defer ResetValidationMetricsInstance()
+
+	// Increment both metrics
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+	Metrics.EmitDeclarativeValidationPanicMetric()
+
+	// Reset the metrics
+	Metrics.Reset()
+
+	// Verify they've been reset to zero
+	expected := `
+	# HELP apiserver_validation_declarative_validation_mismatch_total [BETA] Number of times declarative validation results differed from handwritten validation results for core types.
+	# TYPE apiserver_validation_declarative_validation_mismatch_total counter
+	apiserver_validation_declarative_validation_mismatch_total 0
+	# HELP apiserver_validation_declarative_validation_panic_total [BETA] Number of times declarative validation has panicked during validation.
+	# TYPE apiserver_validation_declarative_validation_panic_total counter
+	apiserver_validation_declarative_validation_panic_total 0
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_mismatch_total", "declarative_validation_panic_total"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Increment the metrics again to ensure they're still functional
+	Metrics.EmitDeclarativeValidationMismatchMetric()
+	Metrics.EmitDeclarativeValidationPanicMetric()
+
+	// Verify they've been incremented correctly
+	expected = `
+	# HELP apiserver_validation_declarative_validation_mismatch_total [BETA] Number of times declarative validation results differed from handwritten validation results for core types.
+	# TYPE apiserver_validation_declarative_validation_mismatch_total counter
+	apiserver_validation_declarative_validation_mismatch_total 1
+	# HELP apiserver_validation_declarative_validation_panic_total [BETA] Number of times declarative validation has panicked during validation.
+	# TYPE apiserver_validation_declarative_validation_panic_total counter
+	apiserver_validation_declarative_validation_panic_total 1
+	`
+
+	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(expected), "declarative_validation_mismatch_total", "declarative_validation_panic_total"); err != nil {
+		t.Fatal(err)
+	}
+}


Reviews:
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-07T18:25:19Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T18:36:02Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T18:38:52Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T20:36:27Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-07T21:13:08Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T21:16:49Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T21:20:08Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-07T21:35:38Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T21:41:42Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-07T22:01:48Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T23:32:27Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-07T23:54:57Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T00:05:49Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T00:55:28Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T01:01:54Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T01:10:18Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T01:16:47Z
user: login: thockin
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-08T01:33:22Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T02:01:50Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-08T20:26:56Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-08T21:08:42Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T01:19:58Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T21:12:29Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T21:14:20Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T21:16:08Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T22:23:51Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T22:36:38Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T23:04:13Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T23:05:27Z
user: login: thockin
body: Overalll it looks good.  It's a little twisty, but I am not sure it can be much simpler.
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T23:24:50Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T23:28:51Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-09T23:41:14Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-09T23:57:54Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T00:26:14Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T00:37:44Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T01:29:24Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T01:30:55Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T01:44:58Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T01:58:55Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T02:00:05Z
user: login: jpbetz
state: COMMENTED
author_association: OWNER
submitted_at: 2025-03-10T02:03:40Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T02:10:35Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T02:10:44Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T06:02:38Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T17:32:25Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T19:15:47Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T19:28:49Z
user: login: thockin
body: Are we going to end up with an e2e test change that asserts the metrics are always 0?

My main concern is making sure that if WE break something around this, CI will fail.
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T21:19:48Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T21:36:59Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T21:37:30Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T21:38:23Z
user: login: aaron-prindle
state: COMMENTED
author_association: COLLABORATOR
submitted_at: 2025-03-10T21:38:43Z

Review comments:
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: The vast majority of requests to the API server are valid.  Having that path be alloc free seems valuable.  Should this function short-circuit beforer this allow if the inputs are length 0?
created_at: 2025-03-07T18:11:46Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Why accumulate coveredImperative and then loop a second time instead of gating with `if !err.CoveredByDeclarative { continue}` in a single loop?
created_at: 2025-03-07T18:13:41Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Let's phrase this differently.

If the system is working correctly this should never happen, so being extra clear on what went wrong, the severity of it, and what action the user should take is worth including here.

I'm thinking phrasing along the lines of:

"Unexpected difference between hand written validation and declarative validation error results ... "
"this indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem" (if applicable)

created_at: 2025-03-07T18:21:34Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
+					matcher.Render(iErr),
+				),
+			)
+		}
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Extra error in declarative validation not found among imperative errors marked as CoveredByDeclarative: %s",
+					matcher.Render(dErr),
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	// Only proceed if there's a mismatch
+	if len(mismatchDetails) > 0 {
+		// Log information about the mismatch
+		for _, detail := range mismatchDetails {
+			klog.Warning(detail)
+		}
+		// Emit the metric
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Sorry if this is written down elsewhere, but is this metric documented as counting the # of requests that have a mismatch, or the total number of mismatches encountered?
created_at: 2025-03-07T18:25:14Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: Updated, this logic is now in a single loop now
created_at: 2025-03-07T18:36:02Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: Thanks for flagging this - added the suggested short circuit to the method now:

```
	// short circuit here to minimize allocs for usual case of 0 validation errors
	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
		return mismatchDetails
	}
```

created_at: 2025-03-07T18:38:51Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
+					matcher.Render(iErr),
+				),
+			)
+		}
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Extra error in declarative validation not found among imperative errors marked as CoveredByDeclarative: %s",
+					matcher.Render(dErr),
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	// Only proceed if there's a mismatch
+	if len(mismatchDetails) > 0 {
+		// Log information about the mismatch
+		for _, detail := range mismatchDetails {
+			klog.Warning(detail)
+		}
+		// Emit the metric
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: It should be the total # of mismatches encountered:
```
  # declarative_validation_mismatch_total tracks the number of mismatched valdation results and errors
  # when comparing the outputs of hand-written validations vs declarative validations
```

this code was incorrect given the KEP description above (the code initially was # of requests).  I have fixed this now to the total # of mismatches encountered
created_at: 2025-03-07T20:36:27Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,96 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
+					matcher.Render(iErr),
+				),
+			)
+		}
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Extra error in declarative validation not found among imperative errors marked as CoveredByDeclarative: %s",
+					matcher.Render(dErr),
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	// Only proceed if there's a mismatch
+	if len(mismatchDetails) > 0 {
+		// Log information about the mismatch
+		for _, detail := range mismatchDetails {
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: nit: guarding slice iteration by size is unnecessary and not idiomatic. let's drop it
created_at: 2025-03-07T21:13:08Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,94 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	// Only compare imperative errors that are actually CoveredByDeclarative.
+	coveredImperative := make(field.ErrorList, 0, len(imperativeErrs))
+	for _, err := range imperativeErrs {
+		if err.CoveredByDeclarative {
+			coveredImperative = append(coveredImperative, err)
+		}
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	var mismatchDetails []string
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range coveredImperative {
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: I've updated this now, the text now reads:

```golang
fmt.Sprintf(
	"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
		"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
	matcher.Render(iErr),
),
```

```golang
fmt.Sprintf(
	"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
		"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
	matcher.Render(dErr),
),
```
created_at: 2025-03-07T21:16:49Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,96 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Imperative validation error marked as CoveredByDeclarative but missing from declarative validation: %s",
+					matcher.Render(iErr),
+				),
+			)
+		}
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Extra error in declarative validation not found among imperative errors marked as CoveredByDeclarative: %s",
+					matcher.Render(dErr),
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	// Only proceed if there's a mismatch
+	if len(mismatchDetails) > 0 {
+		// Log information about the mismatch
+		for _, detail := range mismatchDetails {
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: Done
created_at: 2025-03-07T21:20:07Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: I don't love the O(n^2) here but I've mostly convinced myself it is a non-issue in practice (real world practical limit on number of validation errors fora single request  is small).  Leaving this comment to give someone a chance to tell me I'm wrong.
created_at: 2025-03-07T21:22:00Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,134 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"strings"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// TestCheckDeclarativeValidationMismatches tests all scenarios for
+// the checkDeclarativeValidationMismatches function
+func TestCheckDeclarativeValidationMismatches(t *testing.T) {
+	replicasPath := field.NewPath("spec").Child("replicas")
+	minReadySecondsPath := field.NewPath("spec").Child("minReadySeconds")
+	selectorPath := field.NewPath("spec").Child("selector")
+	containersPath := field.NewPath("spec").Child("template").Child("spec").Child("containers")
+
+	tests := []struct {
+		name                    string
+		imperativeErrors        field.ErrorList
+		declarativeErrors       field.ErrorList
+		expectMismatches        bool
+		expectDetailsContaining []string
+	}{
+		{
+			name: "Matching subset of imperative w/ covered and declarative errors- no mismatch",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- missing declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"minReadySeconds",
+			},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- extra declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(containersPath, nil, "extra declarative error E").WithOrigin("foo"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"extra error(s) found",
+				"containers",
+			},
+		},
path: pkg/apis/core/validation/validation_declarative_test.go
user: login: jpbetz
body: Can we test the edges?  I'm confident when I look at both the tests and implementation code that this is right, but when I look at just the tests, I'm less confident, and I want to not only be sure this code is right, but also make sure future edits don't break it.  How about we cover:

- declarative and imperative return 0 errors
- declarative returns multiple errors with origins and the origins are not all the same (match and non-match case) (This is not an edge, but it's a combo I didn't see covered)
- ~declarative and imperative return exactly 1 error (match and non-match cases)~ (OK, this is not a true edge)
- declarative returns 0 errors, imperative returns 1 error (match and non-match cases)
- declarative returns 1 errors, imperative returns 0 error (match and non-match cases)
created_at: 2025-03-07T21:31:57Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,134 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"strings"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// TestCheckDeclarativeValidationMismatches tests all scenarios for
+// the checkDeclarativeValidationMismatches function
+func TestCheckDeclarativeValidationMismatches(t *testing.T) {
+	replicasPath := field.NewPath("spec").Child("replicas")
+	minReadySecondsPath := field.NewPath("spec").Child("minReadySeconds")
+	selectorPath := field.NewPath("spec").Child("selector")
+	containersPath := field.NewPath("spec").Child("template").Child("spec").Child("containers")
+
+	tests := []struct {
+		name                    string
+		imperativeErrors        field.ErrorList
+		declarativeErrors       field.ErrorList
+		expectMismatches        bool
+		expectDetailsContaining []string
+	}{
+		{
+			name: "Matching subset of imperative w/ covered and declarative errors- no mismatch",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- missing declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"minReadySeconds",
+			},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- extra declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(containersPath, nil, "extra declarative error E").WithOrigin("foo"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"extra error(s) found",
+				"containers",
+			},
+		},
path: pkg/apis/core/validation/validation_declarative_test.go
user: login: jpbetz
body: Defining some fields before declaring the test grid, like `errA = field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum")` might make the tests easier to read/write too
created_at: 2025-03-07T21:33:36Z
author_association: OWNER
diff_hunk: @@ -125,10 +128,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		allErrs = append(allErrs, rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)...)
+		// Run declarative validation
+		declarativeErrs := ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Should we guard against panic in declarative validation while rolling this out?
created_at: 2025-03-07T21:35:12Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: +1  In the description I noted some possible alternatives here, I can change to using one of the alternatives mentioned if preferable.: 

> 
> Currently checking that Declarative Validation errors are a subset of Imperative Validation (w/ Covered error) is done by running the matcher across all pairs in the 2 error lists - N x M elements - O(N^2).
> - Have an alternative solution that "buckets" items in a map that is likely faster (O(N) typically I would assume, O(N^2) worst case if all items in same bucket) , not sure if we wanted to solely rely on the matcher though ( eg: if the bucketing will always be correct, etc.) - https://gist.github.com/aaron-prindle/1bc0ef2822baa00e363ea378c531b41c
> - Could do something like the above and compare counts which would be O(N) but currently want to use matcher directly as the final step of identifying a match, perhaps not necessary though
created_at: 2025-03-07T21:41:42Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: OK, great. Good for followup discussion. This LGTM for 1.33
created_at: 2025-03-07T22:01:48Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,134 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"strings"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// TestCheckDeclarativeValidationMismatches tests all scenarios for
+// the checkDeclarativeValidationMismatches function
+func TestCheckDeclarativeValidationMismatches(t *testing.T) {
+	replicasPath := field.NewPath("spec").Child("replicas")
+	minReadySecondsPath := field.NewPath("spec").Child("minReadySeconds")
+	selectorPath := field.NewPath("spec").Child("selector")
+	containersPath := field.NewPath("spec").Child("template").Child("spec").Child("containers")
+
+	tests := []struct {
+		name                    string
+		imperativeErrors        field.ErrorList
+		declarativeErrors       field.ErrorList
+		expectMismatches        bool
+		expectDetailsContaining []string
+	}{
+		{
+			name: "Matching subset of imperative w/ covered and declarative errors- no mismatch",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches:        false,
+			expectDetailsContaining: []string{},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- missing declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"unmatched error(s) found",
+				"minReadySeconds",
+			},
+		},
+		{
+			name: "Non-matching subset of imperative w/ covered and declarative errors- extra declarative error",
+			imperativeErrors: field.ErrorList{
+				field.Invalid(replicasPath, nil, "regular error A"),
+				createCoveredError(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				createCoveredError(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(selectorPath, nil, "regular error D"),
+			},
+			declarativeErrors: field.ErrorList{
+				field.Invalid(minReadySecondsPath, -1, "covered error B").WithOrigin("minimum"),
+				field.Invalid(replicasPath, nil, "covered error C").WithOrigin("minimum"),
+				field.Invalid(containersPath, nil, "extra declarative error E").WithOrigin("foo"),
+			},
+			expectMismatches: true,
+			expectDetailsContaining: []string{
+				"Unexpected difference between hand written validation and declarative validation error results",
+				"extra error(s) found",
+				"containers",
+			},
+		},
path: pkg/apis/core/validation/validation_declarative_test.go
user: login: aaron-prindle
body: I have refactored so that the errs are variables and added test cases for the suggested edge cases mentioned
created_at: 2025-03-07T23:32:27Z
author_association: COLLABORATOR
diff_hunk: @@ -125,10 +128,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		allErrs = append(allErrs, rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)...)
+		// Run declarative validation
+		declarativeErrs := ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: aaron-prindle
body: Added panic recover in Validate and ValidateUpdate:

```go
func() {
	defer func() {
		if r := recover(); r != nil {
			declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
		}
	}()
	declarativeErrs = ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
}()
```

```go
func() {
	defer func() {
		if r := recover(); r != nil {
			declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
		}
	}()
	declarativeErrs = rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
	declarativeErrs = append(declarativeErrs, rest.ValidateUpdateDeclaratively(ctx, nil, legacyscheme.Scheme, obj, old)...)
}()
```
created_at: 2025-03-07T23:54:56Z
author_association: COLLABORATOR
diff_hunk: @@ -125,10 +128,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		allErrs = append(allErrs, rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)...)
+		// Run declarative validation
+		declarativeErrs := ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Thx!  So if a panic happens, declarative validation emits a exactly one error.  That error is guaranteed to not match imperative, so:

- if Takeover is false, imperative results are returned, metric is incremented.

- if takeover is true, error is sent in response, request fails, metric is incremented


This all sounds right to me.
created_at: 2025-03-08T00:05:49Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Oh, I'd failed to notice the package of this file last review pass.  Do we need a copy of this in each api group package?  I was expecting to write once and share
created_at: 2025-03-08T00:54:26Z
author_association: OWNER
diff_hunk: @@ -125,14 +128,31 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation
+		var declarativeErrs field.ErrorList
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
+				}
+			}()
+			declarativeErrs = ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Given that we've got  `ValidateDeclaratively` how about we wrap it with another func, ideally one that lives in a shared package, that does the panic handling?
created_at: 2025-03-08T01:01:30Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Can this live in the same "rest" package as `ValidateDeclaratively`?  I haven't reasoned though the imports and if there will be problems, but if the imports work it might be a good place
created_at: 2025-03-08T01:10:18Z
author_association: OWNER
diff_hunk: @@ -125,14 +128,31 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation
+		var declarativeErrs field.ErrorList
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
+				}
+			}()
+			declarativeErrs = ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: That is, add a `WithRecover` func, maybe in the same package as `ValidateDeclaratively`, that takes a function, with the  `ValidateDeclaratively` signature as an arg and returns a function, also with the same signature as `ValidateDeclaratively`.  Calling the returned function runs the wrapped function and handles any panics.
created_at: 2025-03-08T01:16:47Z
author_association: OWNER
diff_hunk: @@ -47,6 +47,9 @@ import (
 	"sigs.k8s.io/structured-merge-diff/v4/fieldpath"
 )
 
+// Add to package
+var ValidateDeclarativelyFunc = rest.ValidateDeclaratively
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: thockin
body: I don't follow - when will this var ever not be this value?  Comment?
created_at: 2025-03-08T01:17:14Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +128,31 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation
+		var declarativeErrs field.ErrorList
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: thockin
body: Is this logged, too?

Do we want a metric for how often this happens?
created_at: 2025-03-08T01:19:18Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
path: pkg/apis/core/validation/validation_declarative.go
user: login: thockin
body: I don't think we need to recommend disabling the gate.  That is pretty scary and might make people more anxious than this warrants?
created_at: 2025-03-08T01:30:33Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
path: pkg/apis/core/validation/validation_declarative.go
user: login: thockin
body: We might recommend to disable the takeover gate if set.

We might suggest disabling this if we hit a panic


created_at: 2025-03-08T01:31:29Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
path: pkg/apis/core/validation/validation_declarative.go
user: login: thockin
body: Yeah this really doesn't belong here. It doesn't have anything to do with the validation itself.  Do we have a util package under registry somewhere?

Or maybe a validation package under registry?
created_at: 2025-03-08T01:32:40Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
path: pkg/apis/core/validation/validation_declarative.go
user: login: jpbetz
body: Good call.  A un-alarming message when takeover is false and a recommendation to disable takeover when it is true sounds ideal.
created_at: 2025-03-08T02:01:37Z
author_association: OWNER
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: I've moved this to same "rest" package as ValidateDeclaratively for now into the same file and test file:

staging/src/k8s.io/apiserver/pkg/registry/rest/validation.go
staging/src/k8s.io/apiserver/pkg/registry/rest/validation_test.go

created_at: 2025-03-08T20:26:56Z
author_association: COLLABORATOR
diff_hunk: @@ -47,6 +47,9 @@ import (
 	"sigs.k8s.io/structured-merge-diff/v4/fieldpath"
 )
 
+// Add to package
+var ValidateDeclarativelyFunc = rest.ValidateDeclaratively
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: OK, I caught up on this one.

I don't think we should introduce exported mutable global state in this way. I follow how it makes it possible to mock out validation for testing purposes.

The integration test server is not really designed to mock out behavior like this. I do like the signal the integration test provides.  But since a bug free apiserver should never serve mismatches, I don't know of a way to test this behavior from the integration test server, at least not without building capabilities into the server to dependency inject mocks, and I'm not sure that's a direction we should go.  

It might be better to ship without these tests?  We could look into adding similar tests to a package like staging/src/k8s.io/apiserver/pkg/server but I suspect it is quite a lot of work, and I'm not sure it's worth it.  The unit test coverage we already have that shows how mismatches are computed feels good enough to me.
created_at: 2025-03-08T21:08:42Z
author_association: OWNER
diff_hunk: @@ -47,6 +47,9 @@ import (
 	"sigs.k8s.io/structured-merge-diff/v4/fieldpath"
 )
 
+// Add to package
+var ValidateDeclarativelyFunc = rest.ValidateDeclaratively
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: aaron-prindle
body: +1, I agree that this is not ideal and for the reasons noted.  I have removed this test (`test/integration/apiserver/declarative_validation_metrics_test.go`) for now and removed the associated ValidateDeclarativelyFunc indirection that was used by the test (now strategy.go uses ValidateDeclaratively directly).
created_at: 2025-03-09T01:19:57Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +128,31 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation
+		var declarativeErrs field.ErrorList
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
+				}
+			}()
+			declarativeErrs = ValidateDeclarativelyFunc(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: aaron-prindle
body: I have added a WithRecover and WithRecoverUpdate method to validate.go and associated tests in validate_test.go.  Now in strategy.go the call looks like:

```go
declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
```
```go
		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
		declarativeErrs = append(
			declarativeErrs,
			rest.WithRecoverUpdate(rest.ValidateUpdateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj, old)...)

```


created_at: 2025-03-09T21:12:29Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +128,31 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation
+		var declarativeErrs field.ErrorList
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					declarativeErrs = append(declarativeErrs, field.InternalError(nil, fmt.Errorf("panic during declarative validation: %v", r)))
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: aaron-prindle
body: I have updated this so that there is now a new meteri - declarative_validation_panic_total and also logged this.  Additionally I updated this initial logic such that.  

if DeclarativeValidationTakeover=enabled and ValidateDeclaratively panics -> output a validation error (append to the ErroList) stating the panic

if DeclarativeValidationTakeover=disabled and ValidateDeclaratively panics -> log a warning that the panic occured but don't modify the ErrorList in any way
created_at: 2025-03-09T21:14:20Z
author_association: COLLABORATOR
diff_hunk: @@ -0,0 +1,95 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package validation
+
+import (
+	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/klog/v2"
+
+	fldtest "k8s.io/apimachinery/pkg/util/validation/field/testing"
+	validationmetrics "k8s.io/component-base/metrics/prometheus/validation"
+)
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found.  Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		foundMatch := false
+
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This indicates a major bug in the implementation of declarative validation, please disable DeclarativeValidation feature gate to correct this problem",
path: pkg/apis/core/validation/validation_declarative.go
user: login: aaron-prindle
body: I have updated the message here, the messages now have different wording an recommendation based on the enabled/disabled value of DeclarativeValidationTakeover:

```go
recommendation := "This difference should not affect system operation since hand written validation is authoritative."
if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
	recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
}	
	...

mismatchDetails = append(mismatchDetails,
	fmt.Sprintf(
		"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
			"This may indicate an issue with declarative validation. %s",
		matcher.Render(iErr),
		recommendation,
	),
)
	
```
created_at: 2025-03-09T21:16:08Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +125,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Great, looks like we've got a home for all the support code.

The code here in the Update/UpdateValidate functions is going to be duplicated into the strategies for every single kind.  Can we refine the presentation any further?

I'm imagining getting it down to something close to:

```
if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
	// Run declarative validation
	declarativeErrs = rcStrategy.validateDeclaratively(ctx, nil, obj)
	
	// Compare imperative and declarative errors and log + emit metric if there's a mismatch
	rest.CompareDeclarativeErrorsAndEmitMismatches(allErrs, declarativeErrs)
	
	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
		allErrs = append(allErrs.RemoveCoveredByDeclarative(), declarativeErrs...)
	}
}
```

It might make sense to declare validateDeclaratively in rcStrategy initialization. For example:

```
validateDeclaratively = rest.WithRecovery(rest.ValidateDeclaratively)
```

An alternative would be to just add functions like `rest.validateDeclarativelyWithRecover` ?
created_at: 2025-03-09T21:47:33Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ~Can this function be declared generically, eliminating the need for a separate implementation for update?~

EDIT: Nevermind, I thought about this more, and it cannot.
created_at: 2025-03-09T22:36:38Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real validation
+			errs = validateFunc(ctx, options, scheme, obj)
+		}()
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: Why this additional `func()` ?  Doesn't a defer work the same if declared in the surrounding function?

EDIT: example below.
created_at: 2025-03-09T23:04:12Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real validation
+			errs = validateFunc(ctx, options, scheme, obj)
+		}()
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real update validation
+			errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+		}()
+
+		return errs
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ```suggestion
	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
		defer createDeclarativeValidationPanicHandler(&errs)()
		return validateUpdateFunc(ctx, options, scheme, obj, oldObj)
```

?
created_at: 2025-03-09T23:05:27Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: thockin
body: IIUC this is very subtly different than the matcher.Test() logic.  Suppose we have the following:..

Imperative = `(A, B*, C*, D)`
Declarative = `(B, B, C)` 

In particular, there are 2 B, because they have the same field and origin, but different details.  Matcher will consider the imperative B to match both declarative B.  Does that matter here?  Maybe we don't plan do that sort of refactoring while this whole conversion process is going on, but how confident are we?  I guess we will end up with some sort of mapping function for multi-version, so maybe I am just over-worrying?

created_at: 2025-03-09T23:15:47Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +125,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: thockin
body: Is there ever a time we DON'T want to recover?
created_at: 2025-03-09T23:24:01Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: Just wanted to flag the use of a gate here in our utility functions in apiserver.  We do check flags in the apiserver in other places.  But I can't help but wonder if this would be cleaner if we were able to somehow only return the InternalError in this function and avoid burying this feature gate check.
created_at: 2025-03-09T23:28:51Z
author_association: OWNER
diff_hunk: @@ -125,14 +125,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Not today.  When the migration is 100%, I wasn't expecting to keep the recovery.  So I think a `ValidateDeclarativelyWithRecovery` function is fine, but I'm not sure we could include recovery in our `ValidateDeclaratively` function to because it would be backward incompatible to remove it later.
created_at: 2025-03-09T23:41:14Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real validation
+			errs = validateFunc(ctx, options, scheme, obj)
+		}()
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: > Doesn't a defer work the same if declared in the surrounding function?

Not in my testing.  If the additional func() is removed, errs isn't updated properly in the DeclarativeValidationTakeover=enabled case (it is nil when it should be len(1) and the test fails), specifically this line:
```
*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))

```

runs in both cases but the updated errs is only correct w/ the additional `func()`:

w/ additional `func()`:
```
Running tool: /usr/lib/google-golang/bin/go test -timeout 30s -run ^TestWithRecover$ k8s.io/apiserver/pkg/registry/rest

ok  	k8s.io/apiserver/pkg/registry/rest	0.029s
```

w/o additional `func()`:
```
Running tool: /usr/lib/google-golang/bin/go test -timeout 30s -run ^TestWithRecover$ k8s.io/apiserver/pkg/registry/rest

--- FAIL: TestWithRecover (0.00s)
    --- FAIL: TestWithRecover/panic_with_takeover_enabled (0.00s)
        /usr/local/google/home/aprindle/kubernetes/staging/src/k8s.io/apiserver/pkg/registry/rest/validate_test.go:427: WithRecover() gotErrs = field.ErrorList(nil), want field.ErrorList{(*field.Error)(0xc0003d9a40)}
FAIL
FAIL	k8s.io/apiserver/pkg/registry/rest	0.030s
FAIL
```
created_at: 2025-03-09T23:57:53Z
author_association: COLLABORATOR
diff_hunk: @@ -125,14 +125,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: aaron-prindle
body: I have now added:
- rest.ValidateDeclarativelyWithRecover
- rest.ValidateUpdateDeclarativelyWithRecover

directly in validate.go and updated strategy.go to use those new methods.  
created_at: 2025-03-10T00:26:14Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: Oh, I see we're using the flags in `gatherDeclarativeValidationMismatches`.  This is probably fine for now.
created_at: 2025-03-10T00:37:44Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real validation
+			errs = validateFunc(ctx, options, scheme, obj)
+		}()
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: My below example works for me locally:

```
return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
	defer createDeclarativeValidationPanicHandler(&errs)()
	// Call validation
	return validateFunc(ctx, options, scheme, obj)
}
```

I _would_ expect this to fail:

```
return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
	var errs field.ErrorList
	defer createDeclarativeValidationPanicHandler(&errs)()
	// Call validation
	errs = validateFunc(ctx, options, scheme, obj)
	return errs
}
```

because the defer accesses a local variable after it has been returned by value, so I'd expect appends called by a defer to have no effect on the returned value

EDIT: Note the use of a named return in my working example.  Named returns not only declare a variable (and allow bare returns, which should usually be avoided), they are also "assigned to the return value", making it possible for a defer to intercept and modify a return value in this sort of way.
created_at: 2025-03-10T01:29:24Z
author_association: OWNER
diff_hunk: @@ -125,14 +125,23 @@ func (rcStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object)
 func (rcStrategy) Validate(ctx context.Context, obj runtime.Object) field.ErrorList {
 	controller := obj.(*api.ReplicationController)
 	opts := pod.GetValidationOptionsFromPodTemplate(controller.Spec.Template, nil)
+
+	// Run imperative validation
 	allErrs := corevalidation.ValidateReplicationController(controller, opts)
+
+	// If DeclarativeValidation feature gate is enabled, run both validations
 	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidation) {
-		declarativeErrs := rest.ValidateDeclaratively(ctx, nil, legacyscheme.Scheme, obj)
+		// Run declarative validation with panic recovery
+		declarativeErrs := rest.WithRecover(rest.ValidateDeclaratively)(ctx, nil, legacyscheme.Scheme, obj)
path: pkg/registry/core/replicationcontroller/strategy.go
user: login: jpbetz
body: Thanks, the strategy code looks cleaner to me now.
created_at: 2025-03-10T01:30:55Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+		var errs field.ErrorList
+		func() {
+			defer createDeclarativeValidationPanicHandler(&errs)()
+
+			// Call the real validation
+			errs = validateFunc(ctx, options, scheme, obj)
+		}()
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Ah apologies, I missed the named return initially.  You are correct, I have updated my code to be as suggested and removed the additional `func()`


created_at: 2025-03-10T01:44:58Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ```suggestion
		return validateFunc(ctx, options, scheme, obj)
```
created_at: 2025-03-10T01:58:31Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call update validation
+		errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+
+		return errs
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ```suggestion
		return validateUpdateFunc(ctx, options, scheme, obj, oldObj)
```
created_at: 2025-03-10T01:58:48Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call update validation
+		errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+
+		return errs
+	}
+}
+
+// ValidateDeclarativelyWithRecover validates obj against declarative validation tags
+// with panic recovery logic. It uses the API version extracted from ctx and the
+// provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return WithRecover(ValidateDeclaratively)(ctx, nil, scheme, obj)
+}
+
+// ValidateUpdateDeclarativelyWithRecover validates obj and oldObj against declarative
+// validation tags with panic recovery logic. It uses the API version extracted from
+// ctx and the provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateUpdateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return WithRecoverUpdate(ValidateUpdateDeclaratively)(ctx, nil, scheme, obj, oldObj)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ```suggestion
	return WithRecoverUpdate(ValidateUpdateDeclaratively)(ctx, options, scheme, obj, oldObj)
```
created_at: 2025-03-10T01:59:46Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call update validation
+		errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+
+		return errs
+	}
+}
+
+// ValidateDeclarativelyWithRecover validates obj against declarative validation tags
+// with panic recovery logic. It uses the API version extracted from ctx and the
+// provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return WithRecover(ValidateDeclaratively)(ctx, nil, scheme, obj)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: ```suggestion
	return WithRecover(ValidateDeclaratively)(ctx, options, scheme, obj)
```
created_at: 2025-03-10T02:00:02Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call update validation
+		errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+
+		return errs
+	}
+}
+
+// ValidateDeclarativelyWithRecover validates obj against declarative validation tags
+// with panic recovery logic. It uses the API version extracted from ctx and the
+// provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return WithRecover(ValidateDeclaratively)(ctx, nil, scheme, obj)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: jpbetz
body: I believe extending `TestValidateDeclaratively` to also test the Recover functions would have caught this.
created_at: 2025-03-10T02:03:40Z
author_association: OWNER
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Done!
created_at: 2025-03-10T02:10:34Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,171 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
+			if !matchedDeclarative[j] && matcher.Matches(iErr, dErr) {
+				matchedDeclarative[j] = true
+				foundMatch = true
+				break
+			}
+		}
+		if !foundMatch {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	// Any remaining unmatched declarative errors are considered "extra".
+	for j, dErr := range declarativeErrs {
+		if !matchedDeclarative[j] {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					matcher.Render(dErr),
+					recommendation,
+				),
+			)
+		}
+	}
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment metrics and either log or append errors based on feature gate settings.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call validation
+		errs = validateFunc(ctx, options, scheme, obj)
+
+		return errs
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if DeclarativeValidationTakeover=disabled, and adding a validation error if enabled.
+func WithRecoverUpdate(
+	validateUpdateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs)()
+
+		// Call update validation
+		errs = validateUpdateFunc(ctx, options, scheme, obj, oldObj)
+
+		return errs
+	}
+}
+
+// ValidateDeclarativelyWithRecover validates obj against declarative validation tags
+// with panic recovery logic. It uses the API version extracted from ctx and the
+// provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return WithRecover(ValidateDeclaratively)(ctx, nil, scheme, obj)
+}
+
+// ValidateUpdateDeclarativelyWithRecover validates obj and oldObj against declarative
+// validation tags with panic recovery logic. It uses the API version extracted from
+// ctx and the provided scheme for validation.
+//
+// The ctx MUST contain requestInfo, which determines the target API for
+// validation. The obj is converted to the API version using the provided scheme
+// before validation occurs. The scheme MUST have the declarative validation
+// registered for the requested resource/subresource.
+//
+// option should contain any validation options that the declarative validation
+// tags expect.
+//
+// Returns a field.ErrorList containing any validation errors. An internal error
+// is included if requestInfo is missing from the context, if version
+// conversion fails, or if a panic occurs during validation when
+// DeclarativeValidationTakeover is enabled.
+func ValidateUpdateDeclarativelyWithRecovery(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj, oldObj runtime.Object) field.ErrorList {
+	return WithRecoverUpdate(ValidateUpdateDeclaratively)(ctx, nil, scheme, obj, oldObj)
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Apologies, thanks for catching this, fixed now
created_at: 2025-03-10T02:10:44Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: ~~Thanks for noting this delta.  I have updated this so that the imperative errors don't map 1:1 w/ declarative errors but instead now map 1:many.~~

created_at: 2025-03-10T06:02:37Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: ~~From additional conversation, I have also added deduping to the imperative errors s.t. now for a given imperative error there will only be 1 of those errors matched against declarative -> 1:many~~
created_at: 2025-03-10T17:32:24Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: I've updated the code here to be more aligned with the logic in the error matcher, specifically matcher.Test.  I have also added a test case for the above case:
```go
		{
			name: "Declarative returns 1 error, imperative returns 3 matching errors  - no mismatch",
			imperativeErrors: field.ErrorList{
				coveredErrB,
			},
			declarativeErrors: field.ErrorList{
				errB,
				errB,
				errBWithDiffDetail,
			},
			expectMismatches:        false,
			expectDetailsContaining: []string{},
		},
```
created_at: 2025-03-10T19:15:47Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +111,137 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if utilfeature.DefaultFeatureGate.Enabled(features.DeclarativeValidationTakeover) {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+
+	matcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	matchedDeclarative := make([]bool, len(declarativeErrs))
+	// Match each "covered" imperative error to a declarative error.
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+		foundMatch := false
+		for j, dErr := range declarativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: I have also added exact deduping to the imperativeErrs:
```go
	dedupedImperativeErrs := field.ErrorList{}
	for _, err := range imperativeErrs {
		found := false
		for _, existingErr := range dedupedImperativeErrs {
			if exactMatcher.Matches(existingErr, err) {
				found = true
				break
			}
		}
		if !found {
			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
		}
	}
	imperativeErrs = dedupedImperativeErrs
```
created_at: 2025-03-10T19:28:48Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: thockin
body: Can I get you to comment on this block, so future you (or me) doesn't trip over the details?
created_at: 2025-03-10T21:12:34Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: thockin
body: Comment on why we are doing this?
created_at: 2025-03-10T21:12:45Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		tmp := make(field.ErrorList, 0, len(remaining))
+		matchCount := 0
+
+		for _, dErr := range remaining {
+			if fuzzyMatcher.Matches(iErr, dErr) {
+				matchCount++
+			} else {
+				tmp = append(tmp, dErr)
+			}
+		}
+
+		if matchCount == 0 {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					fuzzyMatcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+
+		remaining = tmp
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra"
+	for _, dErr := range remaining {
+		mismatchDetails = append(mismatchDetails,
+			fmt.Sprintf(
+				"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+					"This may indicate an issue with declarative validation. %s",
+				fuzzyMatcher.Render(dErr),
+				recommendation,
+			),
+		)
+	}
+
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment the panic metric and either log or append errors based on the takeover parameter.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList, takeover bool) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if takeover {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecover(
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: thockin
body: Does this need to be a publis symbol now?  It's `rest.WithRecover` but it is very validation-specific.  Can it just fold into `ValidateDeclarativelyWithRecovery`?
created_at: 2025-03-10T21:18:37Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		tmp := make(field.ErrorList, 0, len(remaining))
+		matchCount := 0
+
+		for _, dErr := range remaining {
+			if fuzzyMatcher.Matches(iErr, dErr) {
+				matchCount++
+			} else {
+				tmp = append(tmp, dErr)
+			}
+		}
+
+		if matchCount == 0 {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					fuzzyMatcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+
+		remaining = tmp
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra"
+	for _, dErr := range remaining {
+		mismatchDetails = append(mismatchDetails,
+			fmt.Sprintf(
+				"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+					"This may indicate an issue with declarative validation. %s",
+				fuzzyMatcher.Render(dErr),
+				recommendation,
+			),
+		)
+	}
+
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment the panic metric and either log or append errors based on the takeover parameter.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList, takeover bool) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if takeover {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+	takeover bool,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs, takeover)()
+
+		return validateFunc(ctx, options, scheme, obj)
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecoverUpdate(
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: thockin
body: Same but for update
created_at: 2025-03-10T21:18:45Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Done, added the following comment:
```
	// Dedupe imperative errors of exact error matches as they are
	// not intended and come from (buggy) duplicate validation calls
	// This is necessary as without deduping we could get unmatched
	// imperative errors for cases that are correct (matching)
```
created_at: 2025-03-10T21:36:59Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Done, added the following comment:
```
	// Match each "covered" imperative error to declarative errors.
	// We use a fuzzy matching approach to find corresponding declarative errors
	// for each imperative error marked as CoveredByDeclarative.
	// As matches are found, they're removed from the 'remaining' list.
	// They are removed from `remaining` with a "1:many" mapping: for a given
	// imperative error we mark as matched all matching declarative errors
	// This allows us to:
	// 1. Detect imperative errors that should have matching declarative errors but don't
	// 2. Identify extra declarative errors with no imperative counterpart
	// Both cases indicate issues with the declarative validation implementation
```
created_at: 2025-03-10T21:37:30Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		tmp := make(field.ErrorList, 0, len(remaining))
+		matchCount := 0
+
+		for _, dErr := range remaining {
+			if fuzzyMatcher.Matches(iErr, dErr) {
+				matchCount++
+			} else {
+				tmp = append(tmp, dErr)
+			}
+		}
+
+		if matchCount == 0 {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					fuzzyMatcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+
+		remaining = tmp
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra"
+	for _, dErr := range remaining {
+		mismatchDetails = append(mismatchDetails,
+			fmt.Sprintf(
+				"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+					"This may indicate an issue with declarative validation. %s",
+				fuzzyMatcher.Render(dErr),
+				recommendation,
+			),
+		)
+	}
+
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment the panic metric and either log or append errors based on the takeover parameter.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList, takeover bool) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if takeover {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecover(
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: Fixed, this is private now.  It is likely better to have be private and not folded into `ValidateDeclarativelyWithRecovery` as the testing for withRecover allows for easier mocking of ValidateDeclaratively to hit important edge cases for testing
created_at: 2025-03-10T21:38:23Z
author_association: COLLABORATOR
diff_hunk: @@ -106,3 +109,197 @@ func parseSubresourcePath(subresourcePath string) ([]string, error) {
 	parts := strings.Split(subresourcePath[1:], "/")
 	return parts, nil
 }
+
+// CompareDeclarativeErrorsAndEmitMismatches checks for mismatches between imperative and declarative validation
+// and logs + emits metrics when inconsistencies are found
+func CompareDeclarativeErrorsAndEmitMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) {
+	mismatchDetails := gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs, takeover)
+	for _, detail := range mismatchDetails {
+		// Log information about the mismatch
+		klog.Warning(detail)
+
+		// Increment the metric for the mismatch
+		validationmetrics.Metrics.EmitDeclarativeValidationMismatchMetric()
+	}
+}
+
+// gatherDeclarativeValidationMismatches compares imperative and declarative validation errors
+// and returns detailed information about any mismatches found. Errors are compared via type, field, and origin
+func gatherDeclarativeValidationMismatches(imperativeErrs, declarativeErrs field.ErrorList, takeover bool) []string {
+	var mismatchDetails []string
+	// short circuit here to minimize allocs for usual case of 0 validation errors
+	if len(imperativeErrs) == 0 && len(declarativeErrs) == 0 {
+		return mismatchDetails
+	}
+	// recommendation based on takeover status
+	recommendation := "This difference should not affect system operation since hand written validation is authoritative."
+	if takeover {
+		recommendation = "Consider disabling the DeclarativeValidationTakeover feature gate."
+	}
+	fuzzyMatcher := fldtest.ErrorMatcher{}.ByType().ByField().ByOrigin().RequireOriginWhenInvalid()
+	exactMatcher := fldtest.ErrorMatcher{}.Exactly()
+
+	dedupedImperativeErrs := field.ErrorList{}
+	for _, err := range imperativeErrs {
+		found := false
+		for _, existingErr := range dedupedImperativeErrs {
+			if exactMatcher.Matches(existingErr, err) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			dedupedImperativeErrs = append(dedupedImperativeErrs, err)
+		}
+	}
+	imperativeErrs = dedupedImperativeErrs
+
+	// Create a copy of declarative errors to track remaining ones
+	remaining := make(field.ErrorList, len(declarativeErrs))
+	copy(remaining, declarativeErrs)
+
+	// Match each "covered" imperative error to declarative errors
+	for _, iErr := range imperativeErrs {
+		if !iErr.CoveredByDeclarative {
+			continue
+		}
+
+		tmp := make(field.ErrorList, 0, len(remaining))
+		matchCount := 0
+
+		for _, dErr := range remaining {
+			if fuzzyMatcher.Matches(iErr, dErr) {
+				matchCount++
+			} else {
+				tmp = append(tmp, dErr)
+			}
+		}
+
+		if matchCount == 0 {
+			mismatchDetails = append(mismatchDetails,
+				fmt.Sprintf(
+					"Unexpected difference between hand written validation and declarative validation error results, unmatched error(s) found %s. "+
+						"This may indicate an issue with declarative validation. %s",
+					fuzzyMatcher.Render(iErr),
+					recommendation,
+				),
+			)
+		}
+
+		remaining = tmp
+	}
+
+	// Any remaining unmatched declarative errors are considered "extra"
+	for _, dErr := range remaining {
+		mismatchDetails = append(mismatchDetails,
+			fmt.Sprintf(
+				"Unexpected difference between hand written validation and declarative validation error results, extra error(s) found %s. "+
+					"This may indicate an issue with declarative validation. %s",
+				fuzzyMatcher.Render(dErr),
+				recommendation,
+			),
+		)
+	}
+
+	return mismatchDetails
+}
+
+// createDeclarativeValidationPanicHandler returns a function with panic recovery logic
+// that will increment the panic metric and either log or append errors based on the takeover parameter.
+func createDeclarativeValidationPanicHandler(errs *field.ErrorList, takeover bool) func() {
+	return func() {
+		if r := recover(); r != nil {
+			// Increment the panic metric counter
+			validationmetrics.Metrics.EmitDeclarativeValidationPanicMetric()
+
+			const errorFmt = "panic during declarative validation: %v"
+			if takeover {
+				// If takeover is enabled, output as a validation error as authorative validator panicked and validation should error
+				*errs = append(*errs, field.InternalError(nil, fmt.Errorf(errorFmt, r)))
+			} else {
+				// if takeover not enabled, log the panic as a warning
+				klog.Warningf(errorFmt, r)
+			}
+		}
+	}
+}
+
+// WithRecover wraps a validation function with panic recovery logic.
+// It takes a validation function with the ValidateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecover(
+	validateFunc func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList,
+	takeover bool,
+) func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) field.ErrorList {
+	return func(ctx context.Context, options sets.Set[string], scheme *runtime.Scheme, obj runtime.Object) (errs field.ErrorList) {
+		defer createDeclarativeValidationPanicHandler(&errs, takeover)()
+
+		return validateFunc(ctx, options, scheme, obj)
+	}
+}
+
+// WithRecoverUpdate wraps an update validation function with panic recovery logic.
+// It takes a validation function with the ValidateUpdateDeclaratively signature
+// and returns a function with the same signature.
+// The returned function will execute the wrapped function and handle any panics by
+// incrementing the panic metric, and logging an error message
+// if takeover=false, and adding a validation error if takeover=true.
+func WithRecoverUpdate(
path: staging/src/k8s.io/apiserver/pkg/registry/rest/validate.go
user: login: aaron-prindle
body: done
created_at: 2025-03-10T21:38:43Z
author_association: COLLABORATOR

PR comments:
user: login: yongruilin
created_at: 2025-03-07T19:22:54Z
body: FYI, I've updated the #121  to use a different approach for using the featuregate, may need to rebase once that settle.
author_association: COLLABORATOR
user: login: jpbetz
created_at: 2025-03-10T02:35:06Z
body: LGTM

author_association: OWNER
user: login: aaron-prindle
created_at: 2025-03-10T21:44:50Z
body: > Are we going to end up with an e2e test change that asserts the metrics are always 0?

+1 It likely makes sense to test that in normal operation the metrics are always 0 via an E2E test.  I can add such an E2E test to this PR if we think it is necessary for 1.33.  For such an E2E test, is there a simple way check the cluster metrics for a representative workload or would the whole test have to be bespoke?
author_association: COLLABORATOR