Add fileDescWireFormatByFilename, and handle file_by_filename

reflection/serverreflection.go

@@ -203,6 +203,20 @@ func (s *serverReflectionServer) fileDescContainingExtension(st reflect.Type, ex
 // fd := fileDescContainingExtension()
 // return fd.GetName()
 
+// fileDescWireFormatByFilename returns the file descriptor of file with the given name.
+// TODO exporte and add lock
+func (s *serverReflectionServer) fileDescWireFormatByFilename(name string) ([]byte, error) {
+	fd, ok := s.filenameToDescMap[name]
+	if !ok {
+		return nil, fmt.Errorf("unknown file: %v", name)
+	}
+	b, err := proto.Marshal(fd)
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
 func (s *serverReflectionServer) allExtensionNumbersForType(st reflect.Type) ([]int32, error) {
 	m, ok := reflect.Zero(reflect.PtrTo(st)).Interface().(proto.Message)
 	if !ok {
@@ -225,13 +239,16 @@ func (s *serverReflectionServer) ServerReflectionInfo(stream rpb.ServerReflectio
 		if err != nil {
 			return err
 		}
-		host := in.Host
-		out := &rpb.ServerReflectionResponse{
-			ValidHost:       host,
-			OriginalRequest: in,
-		}
-		switch in.MessageRequest.(type) {
+
+		var response *rpb.FileDescriptorResponse
+		switch req := in.MessageRequest.(type) {
 		case *rpb.ServerReflectionRequest_FileByFilename:
+			b, err := s.fileDescWireFormatByFilename(req.FileByFilename)
+			if err != nil {
+				// TODO grpc error or send message back
+				return err
+			}
+			response = &rpb.FileDescriptorResponse{FileDescriptorProto: [][]byte{b}}
 		case *rpb.ServerReflectionRequest_FileContainingSymbol:
 		case *rpb.ServerReflectionRequest_FileContainingExtension:
 		case *rpb.ServerReflectionRequest_AllExtensionNumbersOfType:
@@ -240,10 +257,15 @@ func (s *serverReflectionServer) ServerReflectionInfo(stream rpb.ServerReflectio
 			return grpc.Errorf(codes.InvalidArgument, "invalid MessageRequest: %v", in.MessageRequest)
 		}
 
+		out := &rpb.ServerReflectionResponse{
+			ValidHost:       in.Host,
+			OriginalRequest: in,
+			MessageResponse: &rpb.ServerReflectionResponse_FileDescriptorResponse{
+				FileDescriptorResponse: response,
+			},
+		}
 		if err := stream.Send(out); err != nil {
 			return err
 		}
 	}
-
-	return nil
 }

reflection/serverreflection_test.go

@@ -5,6 +5,7 @@ import (
 	"sort"
 	"testing"
 
+	"github.com/golang/protobuf/proto"
 	pb "google.golang.org/grpc/reflection/grpc_testing"
 )
 
@@ -113,3 +114,21 @@ func TestAllExtensionNumbersForType(t *testing.T) {
 		}
 	}
 }
+
+// TODO a better test
+func TestFileDescWireFormatByFilename(t *testing.T) {
+	st := reflect.TypeOf(pb.SearchResponse_Result{})
+	fd, _, err := s.fileDescForType(st)
+	if err != nil {
+		t.Fatalf("failed to do fileDescForType for %q", st)
+	}
+	wanted, err := proto.Marshal(fd)
+	if err != nil {
+		t.Fatalf("failed to do Marshal for %q", fd)
+	}
+	b, err := s.fileDescWireFormatByFilename(fd.GetName())
+	t.Logf("fileDescWireFormatByFilename(%q) = %v, %v", fd.GetName(), b, err)
+	if err != nil || !reflect.DeepEqual(b, wanted) {
+		t.Fatalf("fileDescWireFormatByFilename(%q) = %v, %v, want %v, <nil>", fd.GetName(), b, err, wanted)
+	}
+}