fix panic, when service Handler returns (nil, nil)

rpc_util.go

@@ -26,6 +26,7 @@ import (
  "fmt"
  "io"
  "math"
+ "reflect"
  "strings"
  "sync"
  "time"
@@ -641,7 +642,8 @@ func (p *parser) recvMsg(maxReceiveMessageSize int) (pf payloadFormat, msg []byt
 // error if it is too large to be transmitted by grpc. If msg is nil, it
 // generates an empty message.
 func encode(c baseCodec, msg any) ([]byte, error) {
- if msg == nil { // NOTE: typed nils will not be caught by this check
+ if msg == nil ||
+ reflect.ValueOf(msg).IsNil() { // in gRPC, msg must be a ptr(or nil ptr)
  return nil, nil
  }
  b, err := c.Marshal(msg)

rpc_util_test.go

@@ -191,6 +191,24 @@ func (s) TestToRPCErr(t *testing.T) {
  }
 }
 
+func (s) TestNilReply(t *testing.T) {
+ type XxxReply struct {
+ proto.Message
+ }
+
+ handler := func() (any, error) {
+ return func() (*XxxReply, error) {
+ return nil, nil
+ }()
+ }
+
+ reply, _ := handler()
+ raw, err := encode(encoding.GetCodec(protoenc.Name), reply)
+ if err != nil || raw != nil {
+ t.Fatal(err)
+ }
+}
+
 // bmEncode benchmarks encoding a Protocol Buffer message containing mSize
 // bytes.
 func bmEncode(b *testing.B, mSize int) {