use custom marshal/unmarshal interfaces that can preserve marshaler/unmarshaler settings

Author: jhump

jsonpb/jsonpb.go

@@ -74,6 +74,22 @@ type Marshaler struct {
 	OrigName bool
 }
 
+// JSONPBMarshaler is implemented by protobuf messages that customize the
+// way they are marshaled to JSON. Messages that implement this should
+// also implement JSONPBUnmarshaler so that the custom format can be
+// parsed.
+type JSONPBMarshaler interface {
+	MarshalJSONPB(*Marshaler) ([]byte, error)
+}
+
+// JSONPBUnmarshaler is implemented by protobuf messages that customize
+// the way they are unmarshaled from JSON. Messages that implement this
+// should also implement JSONPBMarshaler so that the custom format can be
+// produced.
+type JSONPBUnmarshaler interface {
+	UnmarshalJSONPB(*Unmarshaler, []byte) error
+}
+
 // Marshal marshals a protocol buffer into JSON.
 func (m *Marshaler) Marshal(out io.Writer, pb proto.Message) error {
 	writer := &errWriter{writer: out}
@@ -102,8 +118,8 @@ type wkt interface {
 
 // marshalObject writes a struct to the Writer.
 func (m *Marshaler) marshalObject(out *errWriter, v proto.Message, indent, typeURL string) error {
-	if jsm, ok := v.(json.Marshaler); ok {
-		b, err := jsm.MarshalJSON()
+	if jsm, ok := v.(JSONPBMarshaler); ok {
+		b, err := jsm.MarshalJSONPB(m)
 		if err != nil {
 			return err
 		}
@@ -537,8 +553,8 @@ func (u *Unmarshaler) UnmarshalNext(dec *json.Decoder, pb proto.Message) error {
 	if err := dec.Decode(&inputValue); err != nil {
 		return err
 	}
-	if jsu, ok := pb.(json.Unmarshaler); ok {
-		return jsu.UnmarshalJSON([]byte(inputValue))
+	if jsu, ok := pb.(JSONPBUnmarshaler); ok {
+		return jsu.UnmarshalJSONPB(u, []byte(inputValue))
 	}
 	return u.unmarshalValue(reflect.ValueOf(pb).Elem(), inputValue, nil)
 }