Add fileDescWireFormatContainingSymbol and handle file_containing_symbol

reflection/serverreflection.go

@@ -221,6 +221,40 @@ func (s *serverReflectionServer) fileDescWireFormatByFilename(name string) ([]by
 	return b, nil
 }
 
+func (s *serverReflectionServer) fileDescWireFormatContainingSymbol(name string) ([]byte, error) {
+	var (
+		fd *dpb.FileDescriptorProto
+	)
+	// Check if it's a type name.
+	if st, err := s.typeForName(name); err == nil {
+		fd, _, err = s.fileDescForType(st)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// Check if it's a service name or method name.
+		meta := s.s.Metadata(name)
+		if meta != nil {
+			if enc, ok := meta.([]byte); ok {
+				fd, err = s.decodeFileDesc(enc)
+				if err != nil {
+					return nil, err
+				}
+			}
+		}
+	}
+
+	// Marshal to wire format.
+	if fd != nil {
+		b, err := proto.Marshal(fd)
+		if err != nil {
+			return nil, err
+		}
+		return b, nil
+	}
+	return nil, fmt.Errorf("unknown symbol: %v", name)
+}
+
 func (s *serverReflectionServer) allExtensionNumbersForType(st reflect.Type) ([]int32, error) {
 	m, ok := reflect.Zero(reflect.PtrTo(st)).Interface().(proto.Message)
 	if !ok {
@@ -254,6 +288,12 @@ func (s *serverReflectionServer) ServerReflectionInfo(stream rpb.ServerReflectio
 			}
 			response = &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}}
 		case *rpb.ServerReflectionRequest_FileContainingSymbol:
+			b, err := s.fileDescWireFormatContainingSymbol(req.FileContainingSymbol)
+			if err != nil {
+				// TODO grpc error or send message back
+				return err
+			}
+			response = &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}}
 		case *rpb.ServerReflectionRequest_FileContainingExtension:
 		case *rpb.ServerReflectionRequest_AllExtensionNumbersOfType:
 		case *rpb.ServerReflectionRequest_ListServices: