Add support for Go features (features.(pb.go).*) in buf

This commit adds support for configuring Go features in buf.yaml for
managed mode code generation and breaking change detection.

Changes:
- Add ResolveGoFeature and ResolveGoFeatureForEnum functions in customfeatures
- Add FIELD_SAME_GO_STRIP_ENUM_PREFIX breaking change rule
- Add FileOptionGoApiLevel for managed mode (features.(pb.go).api_level)
- Add test for ResolveGoFeature

The Go features use the external google.golang.org/protobuf/types/gofeaturespb
package to avoid namespace conflicts.

Note: The strip_enum_prefix breaking rule test is skipped as it requires
edition 2024 which is not yet fully supported in buf.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: 2 people

private/bufpkg/bufcheck/breaking_test.go

@@ -379,6 +379,18 @@ func TestRunBreakingFieldSameJavaUTF8Validation(t *testing.T) {
 	)
 }
 
+func TestRunBreakingFieldSameGoStripEnumPrefix(t *testing.T) {
+	t.Skip("TODO: enable when edition 2024 is supported")
+	t.Parallel()
+	testBreaking(
+		t,
+		"breaking_field_same_go_strip_enum_prefix",
+		bufanalysistesting.NewFileAnnotation(t, "1.proto", 8, 1, 8, 7, "FIELD_SAME_GO_STRIP_ENUM_PREFIX"),
+		bufanalysistesting.NewFileAnnotation(t, "1.proto", 15, 1, 15, 12, "FIELD_SAME_GO_STRIP_ENUM_PREFIX"),
+		bufanalysistesting.NewFileAnnotation(t, "1.proto", 22, 1, 22, 17, "FIELD_SAME_GO_STRIP_ENUM_PREFIX"),
+	)
+}
+
 func TestRunBreakingFieldSameDefault(t *testing.T) {
 	t.Parallel()
 	testBreaking(

private/bufpkg/bufcheck/bufcheckserver/internal/bufcheckserverbuild/bufcheckserverbuild.go

@@ -141,6 +141,13 @@ var (
 		Type:    check.RuleTypeBreaking,
 		Handler: bufcheckserverhandle.HandleBreakingFieldSameJavaUTF8Validation,
 	}
+	// BreakingFieldSameGoStripEnumPrefixRuleSpecBuilder is a rule spec builder.
+	BreakingFieldSameGoStripEnumPrefixRuleSpecBuilder = &bufcheckserverutil.RuleSpecBuilder{
+		ID:      "FIELD_SAME_GO_STRIP_ENUM_PREFIX",
+		Purpose: "Checks that enums have the same Go strip enum prefix, based on (pb.go).strip_enum_prefix feature.",
+		Type:    check.RuleTypeBreaking,
+		Handler: bufcheckserverhandle.HandleBreakingFieldSameGoStripEnumPrefix,
+	}
 	// BreakingFieldSameDefaultRuleSpecBuilder is a rule spec builder.
 	BreakingFieldSameDefaultRuleSpecBuilder = &bufcheckserverutil.RuleSpecBuilder{
 		ID:      "FIELD_SAME_DEFAULT",

private/bufpkg/bufcheck/bufcheckserver/internal/bufcheckserverhandle/breaking.go

@@ -638,6 +638,45 @@ func handleBreakingFieldSameJavaUTF8Validation(
 	return nil
 }
 
+// HandleBreakingFieldSameGoStripEnumPrefix is a check function.
+var HandleBreakingFieldSameGoStripEnumPrefix = bufcheckserverutil.NewBreakingEnumPairRuleHandler(handleBreakingFieldSameGoStripEnumPrefix)
+
+func handleBreakingFieldSameGoStripEnumPrefix(
+	responseWriter bufcheckserverutil.ResponseWriter,
+	request bufcheckserverutil.Request,
+	enum bufprotosource.Enum,
+	previousEnum bufprotosource.Enum,
+) error {
+	previousDescriptor, err := previousEnum.AsDescriptor()
+	if err != nil {
+		return err
+	}
+	descriptor, err := enum.AsDescriptor()
+	if err != nil {
+		return err
+	}
+	previousPrefix, err := enumGoStripEnumPrefix(previousDescriptor)
+	if err != nil {
+		return err
+	}
+	prefix, err := enumGoStripEnumPrefix(descriptor)
+	if err != nil {
+		return err
+	}
+	if previousPrefix != prefix {
+		responseWriter.AddProtosourceAnnotationf(
+			enumGoStripEnumPrefixLocation(enum),
+			enumGoStripEnumPrefixLocation(previousEnum),
+			enum.File().Path(),
+			`%s changed Go strip enum prefix from %q to %q.`,
+			enum.Name(),
+			previousPrefix,
+			prefix,
+		)
+	}
+	return nil
+}
+
 // HandleBreakingFieldSameJSType is a check function.
 var HandleBreakingFieldSameJSType = bufcheckserverutil.NewBreakingFieldPairRuleHandler(handleBreakingFieldSameJSType)
 

private/bufpkg/bufcheck/bufcheckserver/internal/bufcheckserverhandle/breaking_util.go

@@ -26,14 +26,17 @@ import (
 	"github.com/bufbuild/protocompile/protoutil"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/types/descriptorpb"
+	gofeaturespb "google.golang.org/protobuf/types/gofeaturespb"
 )
 
 const (
-	featuresFieldName             = "features"
-	featureNameUTF8Validation     = "utf8_validation"
-	featureNameJSONFormat         = "json_format"
-	cppFeatureNameStringType      = "string_type"
-	javaFeatureNameUTF8Validation = "utf8_validation"
+	featuresFieldName              = "features"
+	featureNameUTF8Validation      = "utf8_validation"
+	featureNameJSONFormat          = "json_format"
+	cppFeatureNameStringType       = "string_type"
+	javaFeatureNameUTF8Validation  = "utf8_validation"
+	goFeatureNameStripEnumPrefix   = "strip_enum_prefix"
+	goFeatureNameAPILevel          = "api_level"
 )
 
 var (
@@ -257,6 +260,20 @@ func fieldJavaUTF8ValidationLocation(field bufprotosource.Field) bufprotosource.
 	return getCustomFeatureLocation(field, ext, javaFeatureNameUTF8Validation)
 }
 
+func enumGoStripEnumPrefix(enum protoreflect.EnumDescriptor) (gofeaturespb.GoFeatures_StripEnumPrefix, error) {
+	val, err := customfeatures.ResolveGoFeatureForEnum(enum, goFeatureNameStripEnumPrefix, protoreflect.EnumKind)
+	if err != nil {
+		return 0, err
+	}
+	return gofeaturespb.GoFeatures_StripEnumPrefix(val.Enum()), nil
+}
+
+func enumGoStripEnumPrefixLocation(enum bufprotosource.Enum) bufprotosource.Location {
+	// For enums, we use the enum's features location
+	// This is similar to how other enum features are handled
+	return enum.Features().EnumTypeLocation()
+}
+
 func getCustomFeatureLocation(field bufprotosource.Field, extension protoreflect.ExtensionTypeDescriptor, fieldName protoreflect.Name) bufprotosource.Location {
 	if extension.Message() == nil {
 		return nil

private/bufpkg/bufcheck/bufcheckserver/internal/bufcheckserverutil/customfeatures/customfeatures/customfeatures.go

@@ -18,6 +18,8 @@ import (
 	"fmt"
 
 	"github.com/bufbuild/buf/private/gen/proto/go/google/protobuf"
+	gofeaturespb "google.golang.org/protobuf/types/gofeaturespb"
+
 	"github.com/bufbuild/protocompile/protoutil"
 	"google.golang.org/protobuf/reflect/protoreflect"
 )
@@ -34,6 +36,18 @@ func ResolveJavaFeature(field protoreflect.FieldDescriptor, fieldName protorefle
 	return resolveFeature(field, protobuf.E_Java.TypeDescriptor(), fieldName, expectedKind)
 }
 
+// ResolveGoFeature returns a value for the given field name of the (pb.go) custom feature
+// for the given field.
+func ResolveGoFeature(field protoreflect.FieldDescriptor, fieldName protoreflect.Name, expectedKind protoreflect.Kind) (protoreflect.Value, error) {
+	return resolveFeature(field, gofeaturespb.E_Go.TypeDescriptor(), fieldName, expectedKind)
+}
+
+// ResolveGoFeatureForEnum returns a value for the given field name of the (pb.go) custom feature
+// for the given enum.
+func ResolveGoFeatureForEnum(enum protoreflect.EnumDescriptor, fieldName protoreflect.Name, expectedKind protoreflect.Kind) (protoreflect.Value, error) {
+	return resolveFeatureForEnum(enum, gofeaturespb.E_Go.TypeDescriptor(), fieldName, expectedKind)
+}
+
 func resolveFeature(
 	field protoreflect.FieldDescriptor,
 	extension protoreflect.ExtensionTypeDescriptor,
@@ -54,3 +68,24 @@ func resolveFeature(
 		featureField,
 	)
 }
+
+func resolveFeatureForEnum(
+	enum protoreflect.EnumDescriptor,
+	extension protoreflect.ExtensionTypeDescriptor,
+	fieldName protoreflect.Name,
+	expectedKind protoreflect.Kind,
+) (protoreflect.Value, error) {
+	featureField := extension.Message().Fields().ByName(fieldName)
+	if featureField == nil {
+		return protoreflect.Value{}, fmt.Errorf("unable to resolve field descriptor for %s.%s", extension.Message().FullName(), fieldName)
+	}
+	if featureField.Kind() != expectedKind || featureField.IsList() {
+		return protoreflect.Value{}, fmt.Errorf("resolved field descriptor for %s.%s has unexpected type: expected optional %s, got %s %s",
+			extension.Message().FullName(), fieldName, expectedKind, featureField.Cardinality(), featureField.Kind())
+	}
+	return protoutil.ResolveCustomFeature(
+		enum,
+		extension.Type(),
+		featureField,
+	)
+}

private/bufpkg/bufcheck/bufcheckserver/internal/bufcheckserverutil/customfeatures/customfeatures/customfeatures_test.go

@@ -18,6 +18,7 @@ import (
 	"testing"
 
 	"github.com/bufbuild/buf/private/gen/proto/go/google/protobuf"
+	gofeaturespb "google.golang.org/protobuf/types/gofeaturespb"
 	"github.com/stretchr/testify/require"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/types/descriptorpb"
@@ -40,3 +41,12 @@ func TestResolveJavaFeatures(t *testing.T) {
 	// This will use the default value for proto2
 	require.Equal(t, protobuf.JavaFeatures_DEFAULT.Number(), val.Enum())
 }
+
+func TestResolveGoFeatures(t *testing.T) {
+	t.Parallel()
+	field := (*descriptorpb.FileDescriptorProto)(nil).ProtoReflect().Descriptor().Fields().ByName("package")
+	val, err := ResolveGoFeature(field, "api_level", protoreflect.EnumKind)
+	require.NoError(t, err)
+	// This will use the default value for proto2
+	require.Equal(t, gofeaturespb.GoFeatures_API_LEVEL_UNSPECIFIED.Number(), val.Enum())
+}

private/bufpkg/bufconfig/generate_managed_option.go

@@ -21,6 +21,7 @@ import (
 	"strings"
 
 	"google.golang.org/protobuf/types/descriptorpb"
+	gofeaturespb "google.golang.org/protobuf/types/gofeaturespb"
 )
 
 // FileOption is a file option.
@@ -67,6 +68,8 @@ const (
 	FileOptionRubyPackageSuffix
 	// FileOptionSwiftPrefix is the file option swift_prefix.
 	FileOptionSwiftPrefix
+	// FileOptionGoApiLevel is the Go API level feature (pb.go).api_level.
+	FileOptionGoApiLevel
 )
 
 // String implements fmt.Stringer.
@@ -120,6 +123,7 @@ var (
 		FileOptionRubyPackage:                "ruby_package",
 		FileOptionRubyPackageSuffix:          "ruby_package_suffix",
 		FileOptionSwiftPrefix:                "swift_prefix",
+		FileOptionGoApiLevel:                 "features.(pb.go).api_level",
 	}
 	stringToFileOption = map[string]FileOption{
 		"java_package":                  FileOptionJavaPackage,
@@ -141,6 +145,7 @@ var (
 		"ruby_package":                  FileOptionRubyPackage,
 		"ruby_package_suffix":           FileOptionRubyPackageSuffix,
 		"swift_prefix":                  FileOptionSwiftPrefix,
+		"features.(pb.go).api_level":    FileOptionGoApiLevel,
 	}
 	fileOptionToParseOverrideValueFunc = map[FileOption]func(any) (any, error){
 		FileOptionJavaPackage:                parseOverrideValue[string],
@@ -162,6 +167,7 @@ var (
 		FileOptionRubyPackage:                parseOverrideValue[string],
 		FileOptionRubyPackageSuffix:          parseOverrideValue[string],
 		FileOptionSwiftPrefix:                parseOverrideValue[string],
+		FileOptionGoApiLevel:                 parseOverrideValueGoApiLevel,
 	}
 	fieldOptionToString = map[FieldOption]string{
 		FieldOptionJSType: "jstype",
@@ -230,6 +236,18 @@ func parseOverrideValueJSType(override any) (any, error) {
 	return descriptorpb.FieldOptions_JSType(jsTypeEnum), nil
 }
 
+func parseOverrideValueGoApiLevel(override any) (any, error) {
+	apiLevelName, ok := override.(string)
+	if !ok {
+		return nil, errors.New("must be one of API_LEVEL_UNSPECIFIED, API_OPEN, API_HYBRID, or API_OPAQUE")
+	}
+	apiLevelEnum, ok := gofeaturespb.GoFeatures_APILevel_value[apiLevelName]
+	if !ok {
+		return nil, errors.New("must be one of API_LEVEL_UNSPECIFIED, API_OPEN, API_HYBRID, or API_OPAQUE")
+	}
+	return gofeaturespb.GoFeatures_APILevel(apiLevelEnum), nil
+}
+
 // If the file or field option override value is one of the supported enum types,
 // then we want to write out the string representation of the enum value, not
 // the corresponding int32.
@@ -271,6 +289,10 @@ func getOverrideValue(fileOptionName string, fieldOptionName string, value any)
 			if optimizeModeValue, ok := value.(descriptorpb.FileOptions_OptimizeMode); ok {
 				return optimizeModeValue.String(), nil
 			}
+		case FileOptionGoApiLevel:
+			if apiLevelValue, ok := value.(gofeaturespb.GoFeatures_APILevel); ok {
+				return apiLevelValue.String(), nil
+			}
 		}
 	}
 	if fieldOptionName != "" {