feat(AIP-148): add uid-format rule (#1270)

As mandated in AIP-148, the `uid` field **must** have `(google.api.field_info).format = UUID4`. This rule enforces that.

Also fix incorrect doc title for `use-uid` rule doc.

docs/rules/0148/uid-format.md

@@ -0,0 +1,79 @@
+---
+rule:
+  aip: 148
+  name: [core, '0148', uid-format]
+  summary: Annotate uid with UUID4 format.
+permalink: /148/uid-format
+redirect_from:
+  - /0148/uid-format
+---
+
+# `uid` format annotation
+
+This rule encourages the use of the `UUID4` format annotation on the `uid`
+field, as mandated in [AIP-148][].
+
+## Details
+
+This rule looks on for fields named `uid` and complains if it does not have the
+`(google.api.field_info).format = UUID4` annotation or has a format other than
+`UUID4`.
+
+## 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 [(google.api.field_behavior) = IDENTIFIER];
+  string uid = 2; // missing (google.api.field_info).format = UUID4
+}
+```
+
+**Correct** code for this rule:
+
+```proto
+// Correct.
+message Book {
+  option (google.api.resource) = {
+    type: "library.googleapis.com/Book"
+    pattern: "books/{book}"
+  };
+
+  string name = 1 [(google.api.field_behavior) = IDENTIFIER];
+  string uid = 2 [(google.api.field_info).format = UUID4];
+}
+```
+
+## Disabling
+
+If you need to violate this rule, use a leading comment above the field or its
+enclosing message. 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) = IDENTIFIER];
+
+  // (-- api-linter: core::0148::uid-format=disabled
+  //     aip.dev/not-precedent: We need to do this because reasons. --)
+  string uid = 2;
+}
+```
+
+If you need to violate this rule for an entire file, place the comment at the
+top of the file.
+
+[aip-148]: https://aip.dev/148
+[aip.dev/not-precedent]: https://aip.dev/not-precedent

docs/rules/0148/use-uid.md

@@ -8,7 +8,7 @@ redirect_from:
   - /0148/use-uid
 ---
 
-# Human names
+# Use `uid` as the resource ID field
 
 This rule encourages the use of `uid` instead of `id` for resource messages, as
 mandated in [AIP-148][].

rules/aip0148/aip0148.go

@@ -27,5 +27,6 @@ func AddRules(r lint.RuleRegistry) error {
 		fieldBehavior,
 		humanNames,
 		useUid,
+		uidFormat,
 	)
 }

rules/aip0148/uid_format.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 aip0148
+
+import (
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+	"github.com/jhump/protoreflect/desc"
+	"google.golang.org/genproto/googleapis/api/annotations"
+	"google.golang.org/protobuf/types/descriptorpb"
+)
+
+var uidFormat = &lint.FieldRule{
+	Name: lint.NewRuleName(148, "uid-format"),
+	OnlyIf: func(fd *desc.FieldDescriptor) bool {
+		return fd.GetType() == descriptorpb.FieldDescriptorProto_TYPE_STRING && fd.GetName() == uidStr
+	},
+	LintField: func(fd *desc.FieldDescriptor) []lint.Problem {
+		if !utils.HasFormat(fd) || utils.GetFormat(fd) != annotations.FieldInfo_UUID4 {
+			return []lint.Problem{{
+				Message:    "The `uid` field must have a `(google.api.field_info).format = UUID4` annotation.",
+				Descriptor: fd,
+			}}
+		}
+
+		return nil
+	},
+}

rules/aip0148/uid_format_test.go

@@ -0,0 +1,74 @@
+// 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 aip0148
+
+import (
+	"testing"
+
+	"github.com/googleapis/api-linter/rules/internal/testutils"
+)
+
+func TestUidFormat(t *testing.T) {
+	for _, test := range []struct {
+		name, Annotation, FieldName, Type string
+		problems                          testutils.Problems
+	}{
+		{
+			name:       "ValidUidFormat",
+			FieldName:  "uid",
+			Annotation: "[(google.api.field_info).format = UUID4]",
+			Type:       "string",
+		},
+		{
+			name:      "SkipNonUid",
+			FieldName: "other",
+			Type:      "string",
+		},
+		{
+			name:      "SkipNonStringUid",
+			FieldName: "uid",
+			Type:      "Foo",
+		},
+		{
+			name:      "InvalidMissingFormat",
+			FieldName: "uid",
+			Type:      "string",
+			problems:  testutils.Problems{{Message: "format = UUID4"}},
+		},
+		{
+			name:       "InvalidWrongFormat",
+			FieldName:  "uid",
+			Annotation: "[(google.api.field_info).format = IPV4]",
+			Type:       "string",
+			problems:   testutils.Problems{{Message: "format = UUID4"}},
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			f := testutils.ParseProto3Tmpl(t, `
+				import "google/api/field_info.proto";
+
+				message Person {
+					{{.Type}} {{.FieldName}} = 2 {{.Annotation}};
+				}
+
+				message Foo {}
+			`, test)
+			field := f.GetMessageTypes()[0].GetFields()[0]
+			if diff := test.problems.SetDescriptor(field).Diff(uidFormat.Lint(f)); diff != "" {
+				t.Errorf(diff)
+			}
+		})
+	}
+}