deps: fix backwards compatibility with encoding (#6965)

encoding/proto/proto.go

@@ -25,6 +25,7 @@ import (
 
 	"google.golang.org/grpc/encoding"
 	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/protoadapt"
 )
 
 // Name is the name registered for the proto compressor.
@@ -38,21 +39,34 @@ func init() {
 type codec struct{}
 
 func (codec) Marshal(v any) ([]byte, error) {
-	vv, ok := v.(proto.Message)
-	if !ok {
+	vv := messageV2Of(v)
+	if vv == nil {
 		return nil, fmt.Errorf("failed to marshal, message is %T, want proto.Message", v)
 	}
+
 	return proto.Marshal(vv)
 }
 
 func (codec) Unmarshal(data []byte, v any) error {
-	vv, ok := v.(proto.Message)
-	if !ok {
-		return fmt.Errorf("failed to unmarshal, message is %T, want proto.Message", v)
+	vv := messageV2Of(v)
+	if vv == nil {
+		return fmt.Errorf("failed to marshal, message is %T, want proto.Message", v)
 	}
+
 	return proto.Unmarshal(data, vv)
 }
 
+func messageV2Of(v any) proto.Message {
+	switch v := v.(type) {
+	case protoadapt.MessageV1:
+		return protoadapt.MessageV2Of(v)
+	case protoadapt.MessageV2:
+		return v
+	}
+
+	return nil
+}
+
 func (codec) Name() string {
 	return Name
 }