feat(AIP-136): request message name (#1386)

[AIP-136](https://google.aip.dev/136)

> Custom methods should take a request message matching the RPC name, with a `Request` suffix.

docs/rules/0136/request-message-name.md

@@ -0,0 +1,71 @@
+---
+rule:
+  aip: 136
+  name: [core, '0136', request-message-name]
+  summary: Custom methods must have standardized request message names.
+permalink: /136/request-message-name
+redirect_from:
+  - /0136/request-message-name
+---
+
+# Custom methods: Request message
+
+This rule enforces that all custom methods should take a request message
+matching the RPC name, with a `Request` suffix [AIP-136][].
+
+## Details
+
+This rule looks at any method that is not a standard method, and complains if
+the name of the corresponding input message does not match the name of the RPC
+with the suffix `Request` appended.
+
+## Examples
+
+**Incorrect** code for this rule:
+
+```proto
+// Incorrect.
+// Should be `ArchiveBookRequest`.
+rpc ArchiveBook(Book) returns (ArchiveBookResponse) {
+  option (google.api.http) = {
+    post: "/v1/{name=publishers/*/books/*}:archive"
+    body: "*"
+  };
+}
+
+```
+
+**Correct** code for this rule:
+
+```proto
+// Correct.
+rpc ArchiveBook(ArchiveBookRequest) returns (ArchiveBookResponse) {
+  option (google.api.http) = {
+    post: "/v1/{name=publishers/*/books/*}:archive"
+    body: "*"
+  };
+}
+
+```
+
+## Disabling
+
+If you need to violate this rule, use a leading comment above the method.
+Remember to also include an [aip.dev/not-precedent][] comment explaining why.
+
+```proto
+// (-- api-linter: core::0136::request-message-name=disabled
+//     aip.dev/not-precedent: We need to do this because reasons. --)
+rpc ArchiveBook(Book) returns (ArchiveBookResponse) {
+  option (google.api.http) = {
+    post: "/v1/{name=publishers/*/books/*}:archive"
+    body: "*"
+  };
+}
+```
+
+If you need to violate this rule for an entire file, place the comment at the
+top of the file.
+
+[aip-136]: https://aip.dev/136
+[aip.dev/not-precedent]: https://aip.dev/not-precedent

rules/aip0136/aip0136.go

@@ -31,6 +31,7 @@ func AddRules(r lint.RuleRegistry) error {
 		httpBody,
 		httpMethod,
 		noPrepositions,
+		requestMessageName,
 		standardMethodsOnly,
 		uriSuffix,
 		verbNoun,

rules/aip0136/request_message_name.go

@@ -0,0 +1,27 @@
+// Copyright 2019 Google LLC
+//
+// 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
+//
+//     https://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 aip0136
+
+import (
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+)
+
+// Custom methods should have a properly named Request message.
+var requestMessageName = &lint.MethodRule{
+	Name:       lint.NewRuleName(136, "request-message-name"),
+	OnlyIf:     isCustomMethod,
+	LintMethod: utils.LintMethodHasMatchingRequestName,
+}

rules/aip0136/request_message_name_test.go

@@ -0,0 +1,52 @@
+// Copyright 2019 Google LLC
+//
+// 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
+//
+//     https://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 aip0136
+
+import (
+	"testing"
+
+	"github.com/googleapis/api-linter/rules/internal/testutils"
+)
+
+func TestRequestMessageName(t *testing.T) {
+	// Set up the testing permutations.
+	tests := []struct {
+		testName       string
+		MethodName     string
+		ReqMessageName string
+		problems       testutils.Problems
+	}{
+		{"Valid", "ArchiveBook", "ArchiveBookRequest", testutils.Problems{}},
+		{"Invalid", "ArchiveBook", "ArchiveBookReq", testutils.Problems{{Suggestion: "ArchiveBookRequest"}}},
+		{"Irrelevant", "DeleteBook", "DeleteRequest", testutils.Problems{}},
+	}
+
+	// Run each test individually.
+	for _, test := range tests {
+		t.Run(test.testName, func(t *testing.T) {
+			f := testutils.ParseProto3Tmpl(t, `
+				service Library {
+					rpc {{.MethodName}}({{.ReqMessageName}}) returns (Book) {}
+				}
+				message {{.ReqMessageName}} {}
+				message Book {}
+			`, test)
+			m := f.GetServices()[0].GetMethods()[0]
+			if diff := test.problems.SetDescriptor(m).Diff(requestMessageName.Lint(f)); diff != "" {
+				t.Errorf(diff)
+			}
+		})
+	}
+}