feat(AIP-203): disallow IDENTIFIER on non-name (#1244)

docs/rules/0203/resource-identifier-only.md

@@ -0,0 +1,77 @@
+---
+rule:
+  aip: 203
+  name: [core, '0203', resource-identifier-only]
+  summary: Only the resource's name field can have field behavior IDENTIFIER.
+permalink: /203/resource-identifier-only
+redirect_from:
+  - /0203/resource-identifier-only
+---
+
+# Resource name: IDENTIFIER
+
+This rule enforces that only the field representing the resource's name is
+annotated with with `(google.api.field_behavior) = IDENTIFIER`, as mandated
+by [AIP-203][].
+
+## Details
+
+This rule looks at every field with `(google.api.field_behavior) = IDENTIFER`
+and complains if that field is not the resource's name field.
+
+## Examples
+
+**Incorrect** code for this rule:
+
+```proto
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1 [(google.api.field_behavior) = IDENTIFER];
+
+  // Incorrect. Must not be assigned IDENTIFIER.
+  string description = 2 [(google.api.field_behavior) = IDENTIFER];
+}
+```
+
+**Correct** code for this rule:
+
+```proto
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
+
+  // Correct.
+  string description = 2;
+}
+```
+
+## Disabling
+
+If you need to violate this rule, use a leading comment above the field.
+Remember to also include an [aip.dev/not-precedent][] comment explaining why.
+
+```proto
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+  string name = 1 [(google.api.field_behavior) = IDENTIFER];
+
+  // (-- api-linter: core::0203::resource-identifier-only=disabled
+  //     aip.dev/not-precedent: We need to do this because reasons. --)
+  string description = 2 [(google.api.field_behavior) = IDENTIFER];
+}
+```
+
+If you need to violate this rule for an entire file, place the comment at the
+top of the file.
+
+[aip-203]: https://aip.dev/203
+[aip.dev/not-precedent]: https://aip.dev/not-precedent

rules/aip0203/aip0203.go

@@ -25,5 +25,6 @@ func AddRules(r lint.RuleRegistry) error {
 		203,
 		fieldBehaviorRequired,
 		unorderedListRepeated,
+		resourceIdentifierOnly,
 	)
 }

rules/aip0203/resource_identifier_only.go

@@ -0,0 +1,39 @@
+// Copyright 2020 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 aip0203
+
+import (
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+	"github.com/jhump/protoreflect/desc"
+)
+
+var resourceIdentifierOnly = &lint.FieldRule{
+	Name: lint.NewRuleName(203, "resource-identifier-only"),
+	OnlyIf: func(f *desc.FieldDescriptor) bool {
+		return utils.GetFieldBehavior(f).Contains("IDENTIFIER")
+	},
+	LintField: func(f *desc.FieldDescriptor) []lint.Problem {
+		m := f.GetParent().(*desc.MessageDescriptor)
+		if nf := utils.GetResourceNameField(utils.GetResource(m)); utils.IsResource(m) && f.GetName() == nf {
+			return nil
+		}
+
+		return []lint.Problem{{
+			Message:    "The IDENTIFIER `google.api.field_behavior` annotation must only be applied to a resource's name field.",
+			Descriptor: f,
+		}}
+	},
+}

rules/aip0203/resource_identifier_only_test.go

@@ -0,0 +1,80 @@
+// 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 aip0203
+
+import (
+	"testing"
+
+	"github.com/googleapis/api-linter/rules/internal/testutils"
+)
+
+func TestResourceIdentifierOnly(t *testing.T) {
+	testCases := []struct {
+		name, message                                   string
+		ResourceField, NameField, NonResourceExtensions string
+		problems                                        testutils.Problems
+	}{
+		{
+			name:          "Valid",
+			message:       "Book",
+			ResourceField: "string name = 1 [(google.api.field_behavior) = IDENTIFIER];",
+			problems:      nil,
+		},
+		{
+			name:          "ValidNameField",
+			message:       "Book",
+			ResourceField: "string resource_name = 1 [(google.api.field_behavior) = IDENTIFIER];",
+			NameField:     "resource_name",
+			problems:      nil,
+		},
+		{
+			name:                  "InvalidNonResource",
+			message:               "NonResource",
+			NonResourceExtensions: "[(google.api.field_behavior) = IDENTIFIER]",
+			problems:              testutils.Problems{{Message: "resource's name field"}},
+		},
+		{
+			name:          "InvalidResourceNonIdentifier",
+			message:       "Book",
+			ResourceField: "string foo = 1 [(google.api.field_behavior) = IDENTIFIER];",
+			problems:      testutils.Problems{{Message: "resource's name field"}},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			file := testutils.ParseProto3Tmpl(t, `
+			import "google/api/field_behavior.proto";
+			import "google/api/resource.proto";
+			message Book {
+				option (google.api.resource) = {
+					type: "library.googleapis.com/Book"
+					pattern: "books/{book}"
+					name_field: "{{.NameField}}"
+				};
+				{{.ResourceField}}
+			}
+			message NonResource {
+				string foo = 1 {{.NonResourceExtensions}};
+			}
+			`, test)
+			f := file.FindMessage(test.message).GetFields()[0]
+			problems := resourceIdentifierOnly.Lint(file)
+			if diff := test.problems.SetDescriptor(f).Diff(problems); diff != "" {
+				t.Error(diff)
+			}
+		})
+	}
+}

rules/internal/utils/resource.go

@@ -49,3 +49,16 @@ func GetResourcePlural(r *apb.ResourceDescriptor) string {
 
 	return r.Plural
 }
+
+// GetResourceNameField is a convenience method for getting the name of the
+// field that represents the resource's name. This is either set by the
+// `name_field` attribute, or defaults to "name".
+func GetResourceNameField(r *apb.ResourceDescriptor) string {
+	if r == nil {
+		return ""
+	}
+	if n := r.GetNameField(); n != "" {
+		return n
+	}
+	return "name"
+}