Repository: googleapis/api-linter

Issue:
AIP-136: Allow SetIamPolicy
Hey @noahdietz,

it would be great to support `SetIamPolicy` as special edge case.

Currently AIP-136 do not allow SetIamPolicy. I think this worked in earlier versions.

Otherwise i really like `core::0136::response-message-name`.

Example:

```proto
  // (-- api-linter: core::0136::response-message-name=disabled
  //     aip.dev/not-precedent: Google. --)     <---- would love to remove this
  rpc SetIamPolicy(google.iam.v1.SetIamPolicyRequest) returns (google.iam.v1.Policy) {
    option (google.api.http) = {
      post: "/v1/{resource=projects/*/users/*}:setIamPolicy"
      body: "*"
    };
    option (google.api.method_signature) = "resource,policy";
  }
```

Thank you 🙏 

Discussion:
@noahdietz: Yeah this makes sense to do.

For posterity, the rule currently expects that the response is a Resource matching the target in the request or a response with a RPC-based named e.g. `SetIamPolicyResponse`. `Policy` isn't annotated as a resource, and it is not the target of the custom method (that would be the `resource` field which is "any resource" for this mixed-in method).

Either we simply allowlist `google.iam.v1.Policy` as an acceptable response type for custom methods knowing it will only be used for the IAM Policy mix in APIs OR we allowlist `rpc SetIamPolicy` specifically. Not sure which is better here, possibly neither is better, rather it "six in one hand, half a dozen in the other". @noahdietz: @quirogas if you don't mind taking a look, this should be a relatively straightforward one 😺 @quirogas: @loeffel-io, this fix will be included in `api-linter` [2.0.1](https://github.com/googleapis/api-linter/pull/1558)

Solution patch:
diff --git a/go.mod b/go.mod
index 5777cd8..4eabfdd 100644
--- a/go.mod
+++ b/go.mod
@@ -4,7 +4,8 @@ go 1.24.0
 
 require (
 	bitbucket.org/creachadair/stringset v0.0.12
-	cloud.google.com/go/longrunning v0.6.7
+	cloud.google.com/go/iam v1.5.3
+	cloud.google.com/go/longrunning v0.7.0
 	github.com/bmatcuk/doublestar/v4 v4.9.1
 	github.com/bufbuild/protocompile v0.14.1
 	github.com/gertd/go-pluralize v0.2.1
@@ -13,18 +14,18 @@ require (
 	github.com/olekukonko/tablewriter v0.0.5
 	github.com/spf13/pflag v1.0.7
 	github.com/stoewer/go-strcase v1.3.1
-	golang.org/x/text v0.28.0
-	google.golang.org/genproto v0.0.0-20250811230008-5f3141c8851a
-	google.golang.org/genproto/googleapis/api v0.0.0-20250811230008-5f3141c8851a
-	google.golang.org/protobuf v1.36.7
+	golang.org/x/text v0.29.0
+	google.golang.org/genproto v0.0.0-20251022142026-3a174f9686a8
+	google.golang.org/genproto/googleapis/api v0.0.0-20251014184007-4626949a642f
+	google.golang.org/protobuf v1.36.10
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
 	github.com/mattn/go-runewidth v0.0.9 // indirect
-	golang.org/x/net v0.42.0 // indirect
-	golang.org/x/sync v0.16.0 // indirect
-	golang.org/x/sys v0.34.0 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20250804133106-a7a43d27e69b // indirect
-	google.golang.org/grpc v1.74.2 // indirect
+	golang.org/x/net v0.44.0 // indirect
+	golang.org/x/sync v0.17.0 // indirect
+	golang.org/x/sys v0.36.0 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20251014184007-4626949a642f // indirect
+	google.golang.org/grpc v1.75.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 376db36..6d39b52 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,9 @@
 bitbucket.org/creachadair/stringset v0.0.12 h1:APD8dIoAzGv70a6p1oasPDjPwkp+ajszdgKyWUcNqo0=
 bitbucket.org/creachadair/stringset v0.0.12/go.mod h1:KtNk2s0hRO1T0r78lv9Zq/S/Lp0du2zI0Fj5j5Y4LDo=
-cloud.google.com/go/longrunning v0.6.7 h1:IGtfDWHhQCgCjwQjV9iiLnUta9LBCo8R9QmAFsS/PrE=
-cloud.google.com/go/longrunning v0.6.7/go.mod h1:EAFV3IZAKmM56TyiE6VAP3VoTzhZzySwI/YI1s/nRsY=
+cloud.google.com/go/iam v1.5.3 h1:+vMINPiDF2ognBJ97ABAYYwRgsaqxPbQDlMnbHMjolc=
+cloud.google.com/go/iam v1.5.3/go.mod h1:MR3v9oLkZCTlaqljW6Eb2d3HGDGK5/bDv93jhfISFvU=
+cloud.google.com/go/longrunning v0.7.0 h1:FV0+SYF1RIj59gyoWDRi45GiYUMM3K1qO51qoboQT1E=
+cloud.google.com/go/longrunning v0.7.0/go.mod h1:ySn2yXmjbK9Ba0zsQqunhDkYi0+9rlXIwnoAf+h+TPY=
 github.com/bmatcuk/doublestar/v4 v4.9.1 h1:X8jg9rRZmJd4yRy7ZeNDRnM+T3ZfHv15JiBJ/avrEXE=
 github.com/bmatcuk/doublestar/v4 v4.9.1/go.mod h1:xBQ8jztBU6kakFMg+8WGxn0c6z1fTSPVIjEY1Wr7jzc=
 github.com/bufbuild/protocompile v0.14.1 h1:iA73zAf/fyljNjQKwYzUHD6AD4R8KMasmwa/FBatYVw=
@@ -43,34 +45,36 @@ github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsT
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
 go.opentelemetry.io/auto/sdk v1.1.0/go.mod h1:3wSPjt5PWp2RhlCcmmOial7AvC4DQqZb7a7wCow3W8A=
-go.opentelemetry.io/otel v1.36.0 h1:UumtzIklRBY6cI/lllNZlALOF5nNIzJVb16APdvgTXg=
-go.opentelemetry.io/otel v1.36.0/go.mod h1:/TcFMXYjyRNh8khOAO9ybYkqaDBb/70aVwkNML4pP8E=
-go.opentelemetry.io/otel/metric v1.36.0 h1:MoWPKVhQvJ+eeXWHFBOPoBOi20jh6Iq2CcCREuTYufE=
-go.opentelemetry.io/otel/metric v1.36.0/go.mod h1:zC7Ks+yeyJt4xig9DEw9kuUFe5C3zLbVjV2PzT6qzbs=
-go.opentelemetry.io/otel/sdk v1.36.0 h1:b6SYIuLRs88ztox4EyrvRti80uXIFy+Sqzoh9kFULbs=
-go.opentelemetry.io/otel/sdk v1.36.0/go.mod h1:+lC+mTgD+MUWfjJubi2vvXWcVxyr9rmlshZni72pXeY=
-go.opentelemetry.io/otel/sdk/metric v1.36.0 h1:r0ntwwGosWGaa0CrSt8cuNuTcccMXERFwHX4dThiPis=
-go.opentelemetry.io/otel/sdk/metric v1.36.0/go.mod h1:qTNOhFDfKRwX0yXOqJYegL5WRaW376QbB7P4Pb0qva4=
-go.opentelemetry.io/otel/trace v1.36.0 h1:ahxWNuqZjpdiFAyrIoQ4GIiAIhxAunQR6MUoKrsNd4w=
-go.opentelemetry.io/otel/trace v1.36.0/go.mod h1:gQ+OnDZzrybY4k4seLzPAWNwVBBVlF2szhehOBB/tGA=
-golang.org/x/net v0.42.0 h1:jzkYrhi3YQWD6MLBJcsklgQsoAcw89EcZbJw8Z614hs=
-golang.org/x/net v0.42.0/go.mod h1:FF1RA5d3u7nAYA4z2TkclSCKh68eSXtiFwcWQpPXdt8=
-golang.org/x/sync v0.16.0 h1:ycBJEhp9p4vXvUZNszeOq0kGTPghopOL8q0fq3vstxw=
-golang.org/x/sync v0.16.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
-golang.org/x/sys v0.34.0 h1:H5Y5sJ2L2JRdyv7ROF1he/lPdvFsd0mJHFw2ThKHxLA=
-golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
-golang.org/x/text v0.28.0 h1:rhazDwis8INMIwQ4tpjLDzUhx6RlXqZNPEM0huQojng=
-golang.org/x/text v0.28.0/go.mod h1:U8nCwOR8jO/marOQ0QbDiOngZVEBB7MAiitBuMjXiNU=
-google.golang.org/genproto v0.0.0-20250811230008-5f3141c8851a h1:V8Zj/61zlL7B+VH151iV5hJlUnYc3fUNTEhLtyr9Kzc=
-google.golang.org/genproto v0.0.0-20250811230008-5f3141c8851a/go.mod h1:q9+ZJOXH/LcpbpkQSsvYReIH5lCcwvfc2xE8JBSER0Q=
-google.golang.org/genproto/googleapis/api v0.0.0-20250811230008-5f3141c8851a h1:DMCgtIAIQGZqJXMVzJF4MV8BlWoJh2ZuFiRdAleyr58=
-google.golang.org/genproto/googleapis/api v0.0.0-20250811230008-5f3141c8851a/go.mod h1:y2yVLIE/CSMCPXaHnSKXxu1spLPnglFLegmgdY23uuE=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20250804133106-a7a43d27e69b h1:zPKJod4w6F1+nRGDI9ubnXYhU9NSWoFAijkHkUXeTK8=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20250804133106-a7a43d27e69b/go.mod h1:qQ0YXyHHx3XkvlzUtpXDkS29lDSafHMZBAZDc03LQ3A=
-google.golang.org/grpc v1.74.2 h1:WoosgB65DlWVC9FqI82dGsZhWFNBSLjQ84bjROOpMu4=
-google.golang.org/grpc v1.74.2/go.mod h1:CtQ+BGjaAIXHs/5YS3i473GqwBBa1zGQNevxdeBEXrM=
-google.golang.org/protobuf v1.36.7 h1:IgrO7UwFQGJdRNXH/sQux4R1Dj1WAKcLElzeeRaXV2A=
-google.golang.org/protobuf v1.36.7/go.mod h1:jduwjTPXsFjZGTmRluh+L6NjiWu7pchiJ2/5YcXBHnY=
+go.opentelemetry.io/otel v1.37.0 h1:9zhNfelUvx0KBfu/gb+ZgeAfAgtWrfHJZcAqFC228wQ=
+go.opentelemetry.io/otel v1.37.0/go.mod h1:ehE/umFRLnuLa/vSccNq9oS1ErUlkkK71gMcN34UG8I=
+go.opentelemetry.io/otel/metric v1.37.0 h1:mvwbQS5m0tbmqML4NqK+e3aDiO02vsf/WgbsdpcPoZE=
+go.opentelemetry.io/otel/metric v1.37.0/go.mod h1:04wGrZurHYKOc+RKeye86GwKiTb9FKm1WHtO+4EVr2E=
+go.opentelemetry.io/otel/sdk v1.37.0 h1:ItB0QUqnjesGRvNcmAcU0LyvkVyGJ2xftD29bWdDvKI=
+go.opentelemetry.io/otel/sdk v1.37.0/go.mod h1:VredYzxUvuo2q3WRcDnKDjbdvmO0sCzOvVAiY+yUkAg=
+go.opentelemetry.io/otel/sdk/metric v1.37.0 h1:90lI228XrB9jCMuSdA0673aubgRobVZFhbjxHHspCPc=
+go.opentelemetry.io/otel/sdk/metric v1.37.0/go.mod h1:cNen4ZWfiD37l5NhS+Keb5RXVWZWpRE+9WyVCpbo5ps=
+go.opentelemetry.io/otel/trace v1.37.0 h1:HLdcFNbRQBE2imdSEgm/kwqmQj1Or1l/7bW6mxVK7z4=
+go.opentelemetry.io/otel/trace v1.37.0/go.mod h1:TlgrlQ+PtQO5XFerSPUYG0JSgGyryXewPGyayAWSBS0=
+golang.org/x/net v0.44.0 h1:evd8IRDyfNBMBTTY5XRF1vaZlD+EmWx6x8PkhR04H/I=
+golang.org/x/net v0.44.0/go.mod h1:ECOoLqd5U3Lhyeyo/QDCEVQ4sNgYsqvCZ722XogGieY=
+golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
+golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
+golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
+golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=
+gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
+gonum.org/v1/gonum v0.16.0/go.mod h1:fef3am4MQ93R2HHpKnLk4/Tbh/s0+wqD5nfa6Pnwy4E=
+google.golang.org/genproto v0.0.0-20251022142026-3a174f9686a8 h1:a12a2/BiVRxRWIqBbfqoSK6tgq8cyUgMnEI81QlPge0=
+google.golang.org/genproto v0.0.0-20251022142026-3a174f9686a8/go.mod h1:1Ic78BnpzY8OaTCmzxJDP4qC9INZPbGZl+54RKjtyeI=
+google.golang.org/genproto/googleapis/api v0.0.0-20251014184007-4626949a642f h1:OiFuztEyBivVKDvguQJYWq1yDcfAHIID/FVrPR4oiI0=
+google.golang.org/genproto/googleapis/api v0.0.0-20251014184007-4626949a642f/go.mod h1:kprOiu9Tr0JYyD6DORrc4Hfyk3RFXqkQ3ctHEum3ZbM=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20251014184007-4626949a642f h1:1FTH6cpXFsENbPR5Bu8NQddPSaUUE6NA2XdZdDSAJK4=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20251014184007-4626949a642f/go.mod h1:7i2o+ce6H/6BluujYR+kqX3GKH+dChPTQU19wjRPiGk=
+google.golang.org/grpc v1.75.1 h1:/ODCNEuf9VghjgO3rqLcfg8fiOP0nSluljWFlDxELLI=
+google.golang.org/grpc v1.75.1/go.mod h1:JtPAzKiq4v1xcAB2hydNlWI2RnF85XXcV0mhKXr2ecQ=
+google.golang.org/protobuf v1.36.10 h1:AYd7cD/uASjIL6Q9LiTjz8JLcrh/88q5UObnmY3aOOE=
+google.golang.org/protobuf v1.36.10/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/rules/aip0136/response_message_name.go b/rules/aip0136/response_message_name.go
index 4bac474..ba7e0dd 100644
--- a/rules/aip0136/response_message_name.go
+++ b/rules/aip0136/response_message_name.go
@@ -40,6 +40,11 @@ var responseMessageName = &lint.MethodRule{
 		// Reference of the input type's `name` field. This guidance is documented
 		// in https://google.aip.dev/136#resource-based-custom-methods
 
+		// SetIamPolicy is a special case since Policy isn't an annotated resource.
+		if m.Name() == "SetIamPolicy" && m.Output().FullName() == "google.iam.v1.Policy" {
+			return nil
+		}
+
 		// Short-circuit: Output type has `Response` suffix
 		suffixFindings := utils.LintMethodHasMatchingResponseName(m)
 		if len(suffixFindings) == 0 {



Test patch:
diff --git a/rules/aip0136/response_message_name_test.go b/rules/aip0136/response_message_name_test.go
index f9a71a6..a44ce54 100644
--- a/rules/aip0136/response_message_name_test.go
+++ b/rules/aip0136/response_message_name_test.go
@@ -56,6 +56,25 @@ func TestResponseMessageName(t *testing.T) {
 		}
 	})
 
+	t.Run("IAM Policy exception", func(t *testing.T) {
+		file := testutils.ParseProto3Tmpl(t, `
+			package test;
+			import "google/api/resource.proto";
+			import "google/iam/v1/policy.proto";
+
+			service Library {
+				rpc SetIamPolicy(SetIamPolicyRequest) returns (google.iam.v1.Policy);
+			}
+
+			message SetIamPolicyRequest {}
+			`, nil)
+		method := file.Services().Get(0).Methods().Get(0)
+		problems := responseMessageName.Lint(file)
+		if diff := (testutils.Problems{}).SetDescriptor(method).Diff(problems); diff != "" {
+			t.Error(diff)
+		}
+	})
+
 	t.Run("Response Suffix - LRO", func(t *testing.T) {
 		// Set up the testing permutations.
 		tests := []struct {
diff --git a/rules/internal/testutils/parse.go b/rules/internal/testutils/parse.go
index 01dd6ac..773308e 100644
--- a/rules/internal/testutils/parse.go
+++ b/rules/internal/testutils/parse.go
@@ -30,6 +30,7 @@ import (
 	// These imports cause the common protos to be registered with
 	// the protocol buffer registry, and therefore make the call to
 	// `proto.FileDescriptor` work for the imported files.
+	_ "cloud.google.com/go/iam/apiv1/iampb"
 	_ "cloud.google.com/go/longrunning/autogen/longrunningpb"
 	_ "google.golang.org/genproto/googleapis/api/annotations"
 	_ "google.golang.org/genproto/googleapis/api/httpbody"