feat(AIP-203): require field_behavior

docs/rules/0203/field-behavior-required.md

@@ -0,0 +1,69 @@
+---
+rule:
+  aip: 203
+  name: [core, '0203', field-behavior-required]
+  summary: Field behavior is required, and must have one of OUTPUT_ONLY,
+  REQUIRED, or OPTIONAL.
+permalink: /203/field-behavior-required
+redirect_from:
+  - /0203/field-behavior-required
+---
+
+# Field Behavior Required
+
+This rule enforces that each field has a `google.api.field_behavior` annotation
+with valid values, as mandated by[AIP-203][]
+
+## Details
+
+This rule looks at all fields and ensures they have a
+`google.api.field_behavior` annotation. It also verifies that they have at least
+one of the options `OUTPUT_ONLY`, `REQUIRED`, or `OPTIONAL`: all fields must
+fall into of these categories.
+
+## Examples
+
+**Incorrect** code for this rule:
+
+```proto
+// Incorrect.
+message Book {
+  string name = 1;
+
+  // No field behavior
+  optional string title = 2;
+}
+```
+
+**Correct** code for this rule:
+
+```proto
+// Correct.
+message Book {
+  string name = 1;
+
+  string title = 2 [(google.api.field_behavior) = REQUIRED];
+}
+```
+
+## 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 {
+  string name = 1;
+
+  // Required. The title of the book.
+  // (-- api-linter: core::0203::field-behavior-required=disabled
+  //     aip.dev/not-precedent: We need to do this because reasons. --)
+  optional string title = 2;
+}
+```
+
+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

docs/rules/0203/required-and-optional.md

@@ -35,7 +35,7 @@ message Book {
 **Correct** code for this rule:
 
 ```proto
-// Incorrect.
+// Correct.
 message Book {
   string name = 1;
 

rules/aip0203/aip0203.go

@@ -31,6 +31,7 @@ var standardFields = stringset.New("etag")
 func AddRules(r lint.RuleRegistry) error {
 	return r.Register(
 		203,
+		fieldBehaviorRequired,
 		inputOnly,
 		immutable,
 		optional,

rules/aip0203/field_behavior_required.go

@@ -0,0 +1,51 @@
+// 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 (
+	"fmt"
+
+	"bitbucket.org/creachadair/stringset"
+	"github.com/googleapis/api-linter/lint"
+	"github.com/googleapis/api-linter/rules/internal/utils"
+	"github.com/jhump/protoreflect/desc"
+)
+
+var requiredOneOfFieldBehavior = stringset.New(
+	"OPTIONAL", "REQUIRED", "OUTPUT_ONLY",
+)
+
+var fieldBehaviorRequired = &lint.FieldRule{
+	Name: lint.NewRuleName(203, "field-behavior-required"),
+	LintField: func(f *desc.FieldDescriptor) []lint.Problem {
+		fieldBehavior := utils.GetFieldBehavior(f)
+		if len(fieldBehavior) == 0 {
+			return []lint.Problem{{
+				Message:    "google.api.field_behavior annotation must be set",
+				Descriptor: f,
+			}}
+		}
+		// check for at least one valid annotation
+		if !requiredOneOfFieldBehavior.Intersects(fieldBehavior) {
+			return []lint.Problem{{
+				Message: fmt.Sprintf(
+					"google.api.field_behavior must have at least one of the following behaviors set: %v",
+					requiredOneOfFieldBehavior,
+				),
+				Descriptor: f,
+			}}
+		}
+		return nil
+	},
+}

rules/aip0203/field_behavior_required_test.go

@@ -0,0 +1,76 @@
+// 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"
+)
+
+const ()
+
+func TestFieldBehaviorRequired(t *testing.T) {
+	for _, test := range []struct {
+		name        string
+		Annotations string
+		problems    testutils.Problems
+	}{
+		{
+			"ValidRequired",
+			"[(google.api.field_behavior) = REQUIRED]",
+			nil,
+		},
+		{
+			"ValidOptional",
+			"[(google.api.field_behavior) = OPTIONAL]",
+			nil,
+		},
+		{
+			"ValidOutputOnly",
+			"[(google.api.field_behavior) = OUTPUT_ONLY]",
+			nil,
+		},
+		{
+			"ValidOptionalImmutable",
+			`[(google.api.field_behavior) = OUTPUT_ONLY,
+			  (google.api.field_behavior) = OPTIONAL]`,
+			nil,
+		},
+		{
+			"InvalidImmutable",
+			"[(google.api.field_behavior) = IMMUTABLE]",
+			testutils.Problems{{Message: "must have at least one"}},
+		},
+		{
+			"InvalidEmpty",
+			"",
+			testutils.Problems{{Message: "annotation must be set"}},
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			f := testutils.ParseProto3Tmpl(t, `
+				import "google/api/field_behavior.proto";
+
+				message Book {
+					int32 page_count = 1 {{.Annotations}};
+				}
+			`, test)
+			field := f.GetMessageTypes()[0].GetFields()[0]
+			if diff := test.problems.SetDescriptor(field).Diff(fieldBehaviorRequired.Lint(f)); diff != "" {
+				t.Errorf(diff)
+			}
+		})
+	}
+}