add plugin annotation, which add a annotation of string for message type, which can be used like JAVA's runtime annotation.

Author: u2takey

gogoproto/gogo.pb.go

@@ -124,6 +124,8 @@ extend google.protobuf.MessageOptions {
 
 	optional bool goproto_sizecache = 64034;
 	optional bool goproto_unkeyed = 64035;
+
+	optional string annotation = 64036;
 }
 
 extend google.protobuf.FieldOptions {

gogoproto/gogo.proto

@@ -306,6 +306,11 @@ func IsUnion(file *google_protobuf.FileDescriptorProto, message *google_protobuf
 	return proto.GetBoolExtension(message.Options, E_Onlyone, proto.GetBoolExtension(file.Options, E_OnlyoneAll, false))
 }
 
+
+func GetStringAnnotation(message *google_protobuf.DescriptorProto) string {
+	return proto.GetStringExtension(message.Options, E_Annotation)
+}
+
 func HasGoString(file *google_protobuf.FileDescriptorProto, message *google_protobuf.DescriptorProto) bool {
 	return proto.GetBoolExtension(message.Options, E_Gostring, proto.GetBoolExtension(file.Options, E_GostringAll, false))
 }

gogoproto/helper.go

@@ -0,0 +1,41 @@
+package annotation
+
+import (
+	"github.com/gogo/protobuf/gogoproto"
+	"github.com/gogo/protobuf/protoc-gen-gogo/generator"
+)
+
+
+type annotation struct {
+	*generator.Generator
+	generator.PluginImports
+}
+
+func NewAnnotation() *annotation {
+	return &annotation{}
+}
+
+func (p *annotation) Name() string {
+	return "annotation"
+}
+
+func (p *annotation) Init(g *generator.Generator) {
+	p.Generator = g
+}
+
+func (p *annotation) Generate(file *generator.FileDescriptor) {
+	p.PluginImports = generator.NewPluginImports(p.Generator)
+	for _, message := range file.Messages() {
+		if gogoproto.GetStringAnnotation(message.DescriptorProto) == "" {
+			continue
+		}
+
+		ccTypeName := generator.CamelCaseSlice(message.TypeName())
+		p.P(`func init(){ proto.RegisterAnnotation(`,
+			`(*`, ccTypeName, ")(nil), `",gogoproto.GetStringAnnotation(message.DescriptorProto) ,"`)}")
+	}
+}
+
+func init() {
+	generator.RegisterPlugin(NewAnnotation())
+}

plugin/annotation/annotation.go

@@ -79,6 +79,21 @@ func GetBoolExtension(pb Message, extension *ExtensionDesc, ifnotset bool) bool
 	return *(value.(*bool))
 }
 
+func GetStringExtension(pb Message, extension *ExtensionDesc) string {
+	if reflect.ValueOf(pb).IsNil() {
+		return ""
+	}
+	value, err := GetExtension(pb, extension)
+	if err != nil {
+		return ""
+	}
+
+	if value.(*string) == nil {
+		return ""
+	}
+	return *(value.(*string))
+}
+
 func (this *Extension) Equal(that *Extension) bool {
 	if err := this.Encode(); err != nil {
 		return false

proto/extensions_gogo.go

@@ -595,6 +595,31 @@ func MessageType(name string) reflect.Type {
 	return protoMapTypes[name]
 }
 
+// A registry of message type's annotations.
+var (
+	annotations = make(map[reflect.Type]string) // message type => annotation
+)
+
+// RegisterAnnotation is called from generated code and maps from the
+// message type to its annotation.
+func RegisterAnnotation(x Message, annotation string) {
+	annotations[reflect.TypeOf(x)] = annotation
+}
+
+// GetAnnotation returns the annotation for a message.
+func GetAnnotation(x Message) string {
+	return annotations[reflect.TypeOf(x)]
+}
+
+// GetAnnotations returns all annotations registered.
+func GetAnnotations() []string {
+	var ret []string
+	for _, v := range annotations {
+		ret = append(ret, v)
+	}
+	return ret
+}
+
 // A registry of all linked proto files.
 var (
 	protoFiles = make(map[string][]byte) // file name => fileDescriptor

proto/properties.go

@@ -548,7 +548,7 @@ func (g *Generator) CommandLineParameters(parameter string) {
 	if pluginList == "none" {
 		pluginList = ""
 	}
-	gogoPluginNames := []string{"unmarshal", "unsafeunmarshaler", "union", "stringer", "size", "protosizer", "populate", "marshalto", "unsafemarshaler", "gostring", "face", "equal", "enumstringer", "embedcheck", "description", "defaultcheck", "oneofcheck", "compare"}
+	gogoPluginNames := []string{"annotation", "unmarshal", "unsafeunmarshaler", "union", "stringer", "size", "protosizer", "populate", "marshalto", "unsafemarshaler", "gostring", "face", "equal", "enumstringer", "embedcheck", "description", "defaultcheck", "oneofcheck", "compare"}
 	pluginList = strings.Join(append(gogoPluginNames, pluginList), "+")
 	if pluginList != "" {
 		// Amend the set of plugins.

protoc-gen-gogo/generator/generator.go

@@ -35,6 +35,7 @@ import (
 	"os"
 	"strings"
 
+	_ "github.com/gogo/protobuf/plugin/annotation"
 	_ "github.com/gogo/protobuf/plugin/compare"
 	_ "github.com/gogo/protobuf/plugin/defaultcheck"
 	_ "github.com/gogo/protobuf/plugin/description"