Repository: zeromicro/go-zero
Pull request #2568 (2022-11-03 16:29:59)

feat: conf inherit


Patch:
diff --git a/core/mapping/fieldoptions.go b/core/mapping/fieldoptions.go
index 37cc13e4..1e8a2ab6 100644
--- a/core/mapping/fieldoptions.go
+++ b/core/mapping/fieldoptions.go
@@ -8,6 +8,7 @@ type (
 	// use context and OptionalDep option to determine the value of Optional
 	// nothing to do with context.Context
 	fieldOptionsWithContext struct {
+		Inherit    bool
 		FromString bool
 		Optional   bool
 		Options    []string
@@ -40,6 +41,10 @@ func (o *fieldOptionsWithContext) getDefault() (string, bool) {
 	return o.Default, len(o.Default) > 0
 }
 
+func (o *fieldOptionsWithContext) inherit() bool {
+	return o != nil && o.Inherit
+}
+
 func (o *fieldOptionsWithContext) optional() bool {
 	return o != nil && o.Optional
 }
diff --git a/core/mapping/unmarshaler.go b/core/mapping/unmarshaler.go
index 3f52f1fb..0f456a35 100644
--- a/core/mapping/unmarshaler.go
+++ b/core/mapping/unmarshaler.go
@@ -70,15 +70,15 @@ func UnmarshalKey(m map[string]interface{}, v interface{}) error {
 
 // Unmarshal unmarshals m into v.
 func (u *Unmarshaler) Unmarshal(m map[string]interface{}, v interface{}) error {
-	return u.UnmarshalValuer(MapValuer(m), v)
+	return u.UnmarshalValuer(mapValuer(m), v)
 }
 
 // UnmarshalValuer unmarshals m into v.
 func (u *Unmarshaler) UnmarshalValuer(m Valuer, v interface{}) error {
-	return u.unmarshalWithFullName(m, v, "")
+	return u.unmarshalWithFullName(simpleValuer{current: m}, v, "")
 }
 
-func (u *Unmarshaler) unmarshalWithFullName(m Valuer, v interface{}, fullName string) error {
+func (u *Unmarshaler) unmarshalWithFullName(m valuerWithParent, v interface{}, fullName string) error {
 	rv := reflect.ValueOf(v)
 	if err := ValidatePtr(&rv); err != nil {
 		return err
@@ -102,7 +102,7 @@ func (u *Unmarshaler) unmarshalWithFullName(m Valuer, v interface{}, fullName st
 }
 
 func (u *Unmarshaler) processAnonymousField(field reflect.StructField, value reflect.Value,
-	m Valuer, fullName string) error {
+	m valuerWithParent, fullName string) error {
 	key, options, err := u.parseOptionsWithContext(field, m, fullName)
 	if err != nil {
 		return err
@@ -120,7 +120,7 @@ func (u *Unmarshaler) processAnonymousField(field reflect.StructField, value ref
 }
 
 func (u *Unmarshaler) processAnonymousFieldOptional(field reflect.StructField, value reflect.Value,
-	key string, m Valuer, fullName string) error {
+	key string, m valuerWithParent, fullName string) error {
 	var filled bool
 	var required int
 	var requiredFilled int
@@ -161,7 +161,7 @@ func (u *Unmarshaler) processAnonymousFieldOptional(field reflect.StructField, v
 }
 
 func (u *Unmarshaler) processAnonymousFieldRequired(field reflect.StructField, value reflect.Value,
-	m Valuer, fullName string) error {
+	m valuerWithParent, fullName string) error {
 	maybeNewValue(field, value)
 	fieldType := Deref(field.Type)
 	indirectValue := reflect.Indirect(value)
@@ -175,8 +175,8 @@ func (u *Unmarshaler) processAnonymousFieldRequired(field reflect.StructField, v
 	return nil
 }
 
-func (u *Unmarshaler) processField(field reflect.StructField, value reflect.Value, m Valuer,
-	fullName string) error {
+func (u *Unmarshaler) processField(field reflect.StructField, value reflect.Value,
+	m valuerWithParent, fullName string) error {
 	if usingDifferentKeys(u.key, field) {
 		return nil
 	}
@@ -189,15 +189,23 @@ func (u *Unmarshaler) processField(field reflect.StructField, value reflect.Valu
 }
 
 func (u *Unmarshaler) processFieldNotFromString(field reflect.StructField, value reflect.Value,
-	mapValue interface{}, opts *fieldOptionsWithContext, fullName string) error {
+	vp valueWithParent, opts *fieldOptionsWithContext, fullName string) error {
 	fieldType := field.Type
 	derefedFieldType := Deref(fieldType)
 	typeKind := derefedFieldType.Kind()
-	valueKind := reflect.TypeOf(mapValue).Kind()
+	valueKind := reflect.TypeOf(vp.value).Kind()
+	mapValue := vp.value
 
 	switch {
 	case valueKind == reflect.Map && typeKind == reflect.Struct:
-		return u.processFieldStruct(field, value, mapValue, fullName)
+		if mv, ok := mapValue.(map[string]interface{}); ok {
+			return u.processFieldStruct(field, value, &simpleValuer{
+				current: mapValuer(mv),
+				parent:  vp.parent,
+			}, fullName)
+		} else {
+			return errTypeMismatch
+		}
 	case valueKind == reflect.Map && typeKind == reflect.Map:
 		return u.fillMap(field, value, mapValue)
 	case valueKind == reflect.String && typeKind == reflect.Map:
@@ -292,18 +300,7 @@ func (u *Unmarshaler) processFieldPrimitiveWithJSONNumber(field reflect.StructFi
 }
 
 func (u *Unmarshaler) processFieldStruct(field reflect.StructField, value reflect.Value,
-	mapValue interface{}, fullName string) error {
-	convertedValue, ok := mapValue.(map[string]interface{})
-	if !ok {
-		valueKind := reflect.TypeOf(mapValue).Kind()
-		return fmt.Errorf("error: field: %s, expect map[string]interface{}, actual %v", fullName, valueKind)
-	}
-
-	return u.processFieldStructWithMap(field, value, MapValuer(convertedValue), fullName)
-}
-
-func (u *Unmarshaler) processFieldStructWithMap(field reflect.StructField, value reflect.Value,
-	m Valuer, fullName string) error {
+	m valuerWithParent, fullName string) error {
 	if field.Type.Kind() == reflect.Ptr {
 		baseType := Deref(field.Type)
 		target := reflect.New(baseType).Elem()
@@ -342,7 +339,7 @@ func (u *Unmarshaler) processFieldTextUnmarshaler(field reflect.StructField, val
 }
 
 func (u *Unmarshaler) processNamedField(field reflect.StructField, value reflect.Value,
-	m Valuer, fullName string) error {
+	m valuerWithParent, fullName string) error {
 	key, opts, err := u.parseOptionsWithContext(field, m, fullName)
 	if err != nil {
 		return err
@@ -353,16 +350,22 @@ func (u *Unmarshaler) processNamedField(field reflect.StructField, value reflect
 	if u.opts.canonicalKey != nil {
 		canonicalKey = u.opts.canonicalKey(key)
 	}
-	mapValue, hasValue := getValue(m, canonicalKey)
-	if hasValue {
-		return u.processNamedFieldWithValue(field, value, mapValue, key, opts, fullName)
+
+	valuer := createValuer(m, opts)
+	mapValue, hasValue := getValue(valuer, canonicalKey)
+	if !hasValue {
+		return u.processNamedFieldWithoutValue(field, value, opts, fullName)
 	}
 
-	return u.processNamedFieldWithoutValue(field, value, opts, fullName)
+	return u.processNamedFieldWithValue(field, value, valueWithParent{
+		value:  mapValue,
+		parent: valuer,
+	}, key, opts, fullName)
 }
 
 func (u *Unmarshaler) processNamedFieldWithValue(field reflect.StructField, value reflect.Value,
-	mapValue interface{}, key string, opts *fieldOptionsWithContext, fullName string) error {
+	vp valueWithParent, key string, opts *fieldOptionsWithContext, fullName string) error {
+	mapValue := vp.value
 	if mapValue == nil {
 		if opts.optional() {
 			return nil
@@ -384,7 +387,7 @@ func (u *Unmarshaler) processNamedFieldWithValue(field reflect.StructField, valu
 	fieldKind := Deref(field.Type).Kind()
 	switch fieldKind {
 	case reflect.Array, reflect.Map, reflect.Slice, reflect.Struct:
-		return u.processFieldNotFromString(field, value, mapValue, opts, fullName)
+		return u.processFieldNotFromString(field, value, vp, opts, fullName)
 	default:
 		if u.opts.fromString || opts.fromString() {
 			valueKind := reflect.TypeOf(mapValue).Kind()
@@ -403,7 +406,7 @@ func (u *Unmarshaler) processNamedFieldWithValue(field reflect.StructField, valu
 			return fillPrimitive(field.Type, value, mapValue, opts, fullName)
 		}
 
-		return u.processFieldNotFromString(field, value, mapValue, opts, fullName)
+		return u.processFieldNotFromString(field, value, vp, opts, fullName)
 	}
 }
 
@@ -431,7 +434,9 @@ func (u *Unmarshaler) processNamedFieldWithoutValue(field reflect.StructField, v
 	switch fieldKind {
 	case reflect.Array, reflect.Map, reflect.Slice:
 		if !opts.optional() {
-			return u.processFieldNotFromString(field, value, emptyMap, opts, fullName)
+			return u.processFieldNotFromString(field, value, valueWithParent{
+				value: emptyMap,
+			}, opts, fullName)
 		}
 	case reflect.Struct:
 		if !opts.optional() {
@@ -439,10 +444,14 @@ func (u *Unmarshaler) processNamedFieldWithoutValue(field reflect.StructField, v
 			if err != nil {
 				return err
 			}
+
 			if required {
 				return fmt.Errorf("%q is not set", fullName)
 			}
-			return u.processFieldNotFromString(field, value, emptyMap, opts, fullName)
+
+			return u.processFieldNotFromString(field, value, valueWithParent{
+				value: emptyMap,
+			}, opts, fullName)
 		}
 	default:
 		if !opts.optional() {
@@ -738,6 +747,20 @@ func WithCanonicalKeyFunc(f func(string) string) UnmarshalOption {
 	}
 }
 
+func createValuer(v valuerWithParent, opts *fieldOptionsWithContext) valuerWithParent {
+	if opts.inherit() {
+		return recursiveValuer{
+			current: v,
+			parent:  v.Parent(),
+		}
+	}
+
+	return simpleValuer{
+		current: v,
+		parent:  v.Parent(),
+	}
+}
+
 func fillDurationValue(fieldKind reflect.Kind, value reflect.Value, dur string) error {
 	d, err := time.ParseDuration(dur)
 	if err != nil {
@@ -805,26 +828,30 @@ func fillWithSameType(field reflect.StructField, value reflect.Value, mapValue i
 }
 
 // getValue gets the value for the specific key, the key can be in the format of parentKey.childKey
-func getValue(m Valuer, key string) (interface{}, bool) {
+func getValue(m valuerWithParent, key string) (interface{}, bool) {
 	keys := readKeys(key)
 	return getValueWithChainedKeys(m, keys)
 }
 
-func getValueWithChainedKeys(m Valuer, keys []string) (interface{}, bool) {
-	if len(keys) == 1 {
+func getValueWithChainedKeys(m valuerWithParent, keys []string) (interface{}, bool) {
+	switch len(keys) {
+	case 0:
+		return nil, false
+	case 1:
 		v, ok := m.Value(keys[0])
 		return v, ok
-	}
-
-	if len(keys) > 1 {
+	default:
 		if v, ok := m.Value(keys[0]); ok {
 			if nextm, ok := v.(map[string]interface{}); ok {
-				return getValueWithChainedKeys(MapValuer(nextm), keys[1:])
+				return getValueWithChainedKeys(recursiveValuer{
+					current: mapValuer(nextm),
+					parent:  m,
+				}, keys[1:])
 			}
 		}
-	}
 
-	return nil, false
+		return nil, false
+	}
 }
 
 func join(elem ...string) string {
diff --git a/core/mapping/utils.go b/core/mapping/utils.go
index 7d8af4df..8d21fd58 100644
--- a/core/mapping/utils.go
+++ b/core/mapping/utils.go
@@ -15,6 +15,7 @@ import (
 
 const (
 	defaultOption      = "default"
+	inheritOption      = "inherit"
 	stringOption       = "string"
 	optionalOption     = "optional"
 	optionsOption      = "options"
@@ -335,6 +336,8 @@ func parseNumberRange(str string) (*numberRange, error) {
 
 func parseOption(fieldOpts *fieldOptions, fieldName, option string) error {
 	switch {
+	case option == inheritOption:
+		fieldOpts.Inherit = true
 	case option == stringOption:
 		fieldOpts.FromString = true
 	case strings.HasPrefix(option, optionalOption):
diff --git a/core/mapping/valuer.go b/core/mapping/valuer.go
index d1a0dfea..e22c877f 100644
--- a/core/mapping/valuer.go
+++ b/core/mapping/valuer.go
@@ -7,12 +7,94 @@ type (
 		Value(key string) (interface{}, bool)
 	}
 
-	// A MapValuer is a map that can use Value method to get values with given keys.
-	MapValuer map[string]interface{}
+	// A valuerWithParent defines a node that has a parent node.
+	valuerWithParent interface {
+		Valuer
+		// Parent get the parent valuer for current node.
+		Parent() valuerWithParent
+	}
+
+	// A node is a map that can use Value method to get values with given keys.
+	node struct {
+		current Valuer
+		parent  valuerWithParent
+	}
+
+	// A valueWithParent is used to wrap the value with its parent.
+	valueWithParent struct {
+		value  interface{}
+		parent valuerWithParent
+	}
+
+	// mapValuer is a type for map to meet the Valuer interface.
+	mapValuer map[string]interface{}
+	// simpleValuer is a type to get value from current node.
+	simpleValuer node
+	// recursiveValuer is a type to get the value recursively from current and parent nodes.
+	recursiveValuer node
 )
 
-// Value gets the value associated with the given key from mv.
-func (mv MapValuer) Value(key string) (interface{}, bool) {
+// Value gets the value assciated with the given key from mv.
+func (mv mapValuer) Value(key string) (interface{}, bool) {
 	v, ok := mv[key]
 	return v, ok
 }
+
+// Value gets the value associated with the given key from sv.
+func (sv simpleValuer) Value(key string) (interface{}, bool) {
+	v, ok := sv.current.Value(key)
+	return v, ok
+}
+
+// Parent get the parent valuer from sv.
+func (sv simpleValuer) Parent() valuerWithParent {
+	if sv.parent == nil {
+		return nil
+	}
+
+	return recursiveValuer{
+		current: sv.parent,
+		parent:  sv.parent.Parent(),
+	}
+}
+
+// Value gets the value associated with the given key from rv,
+// and it will inherit the value from parent nodes.
+func (rv recursiveValuer) Value(key string) (interface{}, bool) {
+	val, ok := rv.current.Value(key)
+	if !ok {
+		if parent := rv.Parent(); parent != nil {
+			return parent.Value(key)
+		}
+
+		return nil, false
+	}
+
+	if vm, ok := val.(map[string]interface{}); ok {
+		if parent := rv.Parent(); parent != nil {
+			pv, pok := parent.Value(key)
+			if pok {
+				if pm, ok := pv.(map[string]interface{}); ok {
+					for k, v := range vm {
+						pm[k] = v
+					}
+					return pm, true
+				}
+			}
+		}
+	}
+
+	return val, true
+}
+
+// Parent get the parent valuer from rv.
+func (rv recursiveValuer) Parent() valuerWithParent {
+	if rv.parent == nil {
+		return nil
+	}
+
+	return recursiveValuer{
+		current: rv.parent,
+		parent:  rv.parent.Parent(),
+	}
+}
diff --git a/zrpc/config.go b/zrpc/config.go
index 36dd0074..225ee2eb 100644
--- a/zrpc/config.go
+++ b/zrpc/config.go
@@ -12,7 +12,7 @@ type (
 	RpcServerConf struct {
 		service.ServiceConf
 		ListenOn      string
-		Etcd          discov.EtcdConf    `json:",optional"`
+		Etcd          discov.EtcdConf    `json:",optional,inherit"`
 		Auth          bool               `json:",optional"`
 		Redis         redis.RedisKeyConf `json:",optional"`
 		StrictControl bool               `json:",optional"`
@@ -25,7 +25,7 @@ type (
 
 	// A RpcClientConf is a rpc client config.
 	RpcClientConf struct {
-		Etcd      discov.EtcdConf `json:",optional"`
+		Etcd      discov.EtcdConf `json:",optional,inherit"`
 		Endpoints []string        `json:",optional"`
 		Target    string          `json:",optional"`
 		App       string          `json:",optional"`


Test patch:
diff --git a/core/mapping/unmarshaler_test.go b/core/mapping/unmarshaler_test.go
index f445817d..e4fd78fd 100644
--- a/core/mapping/unmarshaler_test.go
+++ b/core/mapping/unmarshaler_test.go
@@ -7,10 +7,10 @@ import (
 	"strings"
 	"testing"
 	"time"
+	"unicode"
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
-
 	"github.com/zeromicro/go-zero/core/stringx"
 )
 
@@ -38,6 +38,29 @@ func TestUnmarshalWithoutTagName(t *testing.T) {
 	assert.True(t, in.Optional)
 }
 
+func TestUnmarshalWithoutTagNameWithCanonicalKey(t *testing.T) {
+	type inner struct {
+		Name string `key:"name"`
+	}
+	m := map[string]interface{}{
+		"Name": "go-zero",
+	}
+
+	var in inner
+	unmarshaler := NewUnmarshaler(defaultKeyName, WithCanonicalKeyFunc(func(s string) string {
+		first := true
+		return strings.Map(func(r rune) rune {
+			if first {
+				first = false
+				return unicode.ToTitle(r)
+			}
+			return r
+		}, s)
+	}))
+	assert.Nil(t, unmarshaler.Unmarshal(m, &in))
+	assert.Equal(t, "go-zero", in.Name)
+}
+
 func TestUnmarshalBool(t *testing.T) {
 	type inner struct {
 		True           bool `key:"yes"`
@@ -2718,6 +2741,256 @@ func TestUnmarshalNestedMapSimpleTypeMatch(t *testing.T) {
 	assert.Equal(t, "1", c.Anything["id"])
 }
 
+func TestUnmarshalInheritPrimitiveUseParent(t *testing.T) {
+	type (
+		component struct {
+			Name      string `key:"name"`
+			Discovery string `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery string    `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": "localhost:8080",
+		"component": map[string]interface{}{
+			"name": "test",
+		},
+	}, &s))
+	assert.Equal(t, "localhost:8080", s.Discovery)
+	assert.Equal(t, "localhost:8080", s.Component.Discovery)
+}
+
+func TestUnmarshalInheritPrimitiveUseSelf(t *testing.T) {
+	type (
+		component struct {
+			Name      string `key:"name"`
+			Discovery string `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery string    `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": "localhost:8080",
+		"component": map[string]interface{}{
+			"name":      "test",
+			"discovery": "localhost:8888",
+		},
+	}, &s))
+	assert.Equal(t, "localhost:8080", s.Discovery)
+	assert.Equal(t, "localhost:8888", s.Component.Discovery)
+}
+
+func TestUnmarshalInheritPrimitiveNotExist(t *testing.T) {
+	type (
+		component struct {
+			Name      string `key:"name"`
+			Discovery string `key:"discovery,inherit"`
+		}
+		server struct {
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NotNil(t, UnmarshalKey(map[string]interface{}{
+		"component": map[string]interface{}{
+			"name": "test",
+		},
+	}, &s))
+}
+
+func TestUnmarshalInheritStructUseParent(t *testing.T) {
+	type (
+		discovery struct {
+			Host string `key:"host"`
+			Port int    `key:"port"`
+		}
+		component struct {
+			Name      string    `key:"name"`
+			Discovery discovery `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery discovery `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": map[string]interface{}{
+			"host": "localhost",
+			"port": 8080,
+		},
+		"component": map[string]interface{}{
+			"name": "test",
+		},
+	}, &s))
+	assert.Equal(t, "localhost", s.Discovery.Host)
+	assert.Equal(t, 8080, s.Discovery.Port)
+	assert.Equal(t, "localhost", s.Component.Discovery.Host)
+	assert.Equal(t, 8080, s.Component.Discovery.Port)
+}
+
+func TestUnmarshalInheritStructUseSelf(t *testing.T) {
+	type (
+		discovery struct {
+			Host string `key:"host"`
+			Port int    `key:"port"`
+		}
+		component struct {
+			Name      string    `key:"name"`
+			Discovery discovery `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery discovery `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": map[string]interface{}{
+			"host": "localhost",
+			"port": 8080,
+		},
+		"component": map[string]interface{}{
+			"name": "test",
+			"discovery": map[string]interface{}{
+				"host": "remotehost",
+				"port": 8888,
+			},
+		},
+	}, &s))
+	assert.Equal(t, "localhost", s.Discovery.Host)
+	assert.Equal(t, 8080, s.Discovery.Port)
+	assert.Equal(t, "remotehost", s.Component.Discovery.Host)
+	assert.Equal(t, 8888, s.Component.Discovery.Port)
+}
+
+func TestUnmarshalInheritStructNotExist(t *testing.T) {
+	type (
+		discovery struct {
+			Host string `key:"host"`
+			Port int    `key:"port"`
+		}
+		component struct {
+			Name      string    `key:"name"`
+			Discovery discovery `key:"discovery,inherit"`
+		}
+		server struct {
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NotNil(t, UnmarshalKey(map[string]interface{}{
+		"component": map[string]interface{}{
+			"name": "test",
+		},
+	}, &s))
+}
+
+func TestUnmarshalInheritStructUsePartial(t *testing.T) {
+	type (
+		discovery struct {
+			Host string `key:"host"`
+			Port int    `key:"port"`
+		}
+		component struct {
+			Name      string    `key:"name"`
+			Discovery discovery `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery discovery `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": map[string]interface{}{
+			"host": "localhost",
+			"port": 8080,
+		},
+		"component": map[string]interface{}{
+			"name": "test",
+			"discovery": map[string]interface{}{
+				"port": 8888,
+			},
+		},
+	}, &s))
+	assert.Equal(t, "localhost", s.Discovery.Host)
+	assert.Equal(t, 8080, s.Discovery.Port)
+	assert.Equal(t, "localhost", s.Component.Discovery.Host)
+	assert.Equal(t, 8888, s.Component.Discovery.Port)
+}
+
+func TestUnmarshalInheritStructUseSelfIncorrectType(t *testing.T) {
+	type (
+		discovery struct {
+			Host string `key:"host"`
+			Port int    `key:"port"`
+		}
+		component struct {
+			Name      string    `key:"name"`
+			Discovery discovery `key:"discovery,inherit"`
+		}
+		server struct {
+			Discovery discovery `key:"discovery"`
+			Component component `key:"component"`
+		}
+	)
+
+	var s server
+	assert.NotNil(t, UnmarshalKey(map[string]interface{}{
+		"discovery": map[string]interface{}{
+			"host": "localhost",
+		},
+		"component": map[string]interface{}{
+			"name": "test",
+			"discovery": map[string]string{
+				"host": "remotehost",
+			},
+		},
+	}, &s))
+}
+
+func TestUnmarshaler_InheritFromGrandparent(t *testing.T) {
+	type (
+		component struct {
+			Name      string `key:"name"`
+			Discovery string `key:"discovery,inherit"`
+		}
+		middle struct {
+			Value component `key:"value"`
+		}
+		server struct {
+			Discovery string `key:"discovery"`
+			Middle    middle `key:"middle"`
+		}
+	)
+
+	var s server
+	assert.NoError(t, UnmarshalKey(map[string]interface{}{
+		"discovery": "localhost:8080",
+		"middle": map[string]interface{}{
+			"value": map[string]interface{}{
+				"name": "test",
+			},
+		},
+	}, &s))
+	assert.Equal(t, "localhost:8080", s.Discovery)
+	assert.Equal(t, "localhost:8080", s.Middle.Value.Discovery)
+}
+
 func TestUnmarshalValuer(t *testing.T) {
 	unmarshaler := NewUnmarshaler(jsonTagKey)
 	var foo string
diff --git a/core/mapping/valuer_test.go b/core/mapping/valuer_test.go
new file mode 100644
index 00000000..01ee56f5
--- /dev/null
+++ b/core/mapping/valuer_test.go
@@ -0,0 +1,33 @@
+package mapping
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMapValuerWithInherit_Value(t *testing.T) {
+	input := map[string]interface{}{
+		"discovery": map[string]interface{}{
+			"host": "localhost",
+			"port": 8080,
+		},
+		"component": map[string]interface{}{
+			"name": "test",
+		},
+	}
+	valuer := recursiveValuer{
+		current: mapValuer(input["component"].(map[string]interface{})),
+		parent: simpleValuer{
+			current: mapValuer(input),
+		},
+	}
+
+	val, ok := valuer.Value("discovery")
+	assert.True(t, ok)
+
+	m, ok := val.(map[string]interface{})
+	assert.True(t, ok)
+	assert.Equal(t, "localhost", m["host"])
+	assert.Equal(t, 8080, m["port"])
+}