feat(AIP-122): Flag self-link fields in resources

docs/rules/0122/no-self-links.md

@@ -0,0 +1,76 @@
+---
+rule:
+  aip: 122
+  name: [core, '0122', no-self-links]
+  summary: Resources should not contain self-links.
+permalink: /122/no-self-links
+redirect_from:
+  - /0122/no-self-links
+---
+
+# No self links
+
+This rule enforces that resource messages do not contain any fields called
+`string self_link`, as mandated in [AIP-122][].
+
+## Details
+
+This rule complains if it sees a resource field of type `string` that is also
+named `self_link`.
+
+## Examples
+
+**Incorrect** code for this rule:
+
+```proto
+// Incorrect.
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1;
+
+  // Incorrect. Resources should contain self-links.
+  string self_link = 2;
+}
+```
+
+**Correct** code for this rule:
+
+```proto
+// Correct.
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1;
+}
+```
+
+## 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
+// Incorrect.
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1;
+
+  // (-- api-linter: core::0122::no-self-links=disabled
+  //     aip.dev/not-precedent: We need to do this because reasons. --)
+  string self_link = 2;
+}
+```
+
+If you need to violate this rule for an entire file, place the comment at the
+top of the file.
+
+[aip-122]: https://aip.dev/122
+[aip.dev/not-precedent]: https://aip.dev/not-precedent

rules/aip0122/aip0122.go

@@ -27,6 +27,7 @@ func AddRules(r lint.RuleRegistry) error {
 		resourceCollectionIdentifiers,
 		httpURICase,
 		nameSuffix,
+		noSelfLinks,
 		resourceReferenceType,
 		resourceIdOutputOnly,
 		embeddedResource,

rules/aip0122/no_self_links.go

@@ -0,0 +1,40 @@
+// Copyright 2023 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 aip0122
+
+import (
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+	"github.com/jhump/protoreflect/desc"
+	"google.golang.org/protobuf/types/descriptorpb"
+)
+
+var noSelfLinks = &lint.MessageRule{
+	Name:   lint.NewRuleName(122, "no-self-links"),
+	OnlyIf: utils.IsResource,
+	LintMessage: func(m *desc.MessageDescriptor) []lint.Problem {
+		problems := []lint.Problem{}
+		for _, field := range m.GetFields() {
+			if field.GetType() == descriptorpb.FieldDescriptorProto_TYPE_STRING &&
+				field.GetName() == "self_link" {
+				problems = append(problems, lint.Problem{
+					Message:    "Resources must not contain self-links.",
+					Descriptor: field,
+				})
+			}
+		}
+		return problems
+	},
+}

rules/aip0122/no_self_links_test.go

@@ -0,0 +1,50 @@
+// Copyright 2023 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 aip0122
+
+import (
+	"testing"
+
+	"github.com/googleapis/api-linter/rules/internal/testutils"
+)
+
+func TestNoSelfLinks(t *testing.T) {
+	for _, test := range []struct {
+		name      string
+		FieldName string
+		problems  testutils.Problems
+	}{
+		{"Valid", "author", nil},
+		{"InvalidSelfLink", "self_link", testutils.Problems{{Message: "self-links"}}},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			f := testutils.ParseProto3Tmpl(t, `
+			import "google/api/resource.proto";
+			message Book {
+				option (google.api.resource) = {
+					type: "library.googleapis.com/Book"
+				};
+				string name = 1;
+
+				string {{ .FieldName }} = 2;
+			}
+		`, test)
+			field := f.GetMessageTypes()[0].GetFields()[1]
+			if diff := test.problems.SetDescriptor(field).Diff(noSelfLinks.Lint(f)); diff != "" {
+				t.Errorf(diff)
+			}
+		})
+	}
+}