jsonpb marshaling Any containing dynamic message missing @type

[cybrcodr]

Sample proto file

syntax = "proto2";
package pb;

message Foo {
  optional google.protobuf.Any iany = 1;
}

Sample code that stores a dynamic message into Foo.iany field.

package test

import (
        "strings"
        "testing"

        "test/pb"

        "github.com/golang/protobuf/jsonpb"
        "github.com/golang/protobuf/proto"
        anypb "github.com/golang/protobuf/ptypes/any"
)

type dynamic struct {
        Json []byte `protobuf:"bytes,1,opt,name=json" json:"json,omitempty"`
}

func (d *dynamic) Reset() {
        d.Json = nil
}

func (d *dynamic) String() string {
        return string(d.Json)
}

func (d *dynamic) ProtoMessage() {}

func (d *dynamic) MarshalJSONPB(_ *jsonpb.Marshaler) ([]byte, error) {
        return d.Json, nil
}

func (d *dynamic) UnmarshalJSONPB(_ *jsonpb.Unmarshaler, jstr []byte) error {
        d.Json = jstr
        return nil
}

func init() {
        proto.RegisterType((*dynamic)(nil), "pb.Dynamic")
}

func TestMarshalAnyDynamic(t *testing.T) {
        d := &dynamic{Json: []byte(`{"hello": "world"}`)}
        b, err := proto.Marshal(d)
        if err != nil {
                t.Fatal(err)
        }

        foo := &pb.Foo{
                Iany: &anypb.Any{
                        TypeUrl: "ok.com/pb.Dynamic",
                        Value:   b,
                },
        }

        m := &jsonpb.Marshaler{}
        s, err := m.MarshalToString(foo)
        if err != nil {
                t.Error(err)
        } else {
                t.Log(s)
        }
}

Outputs:

{"iany":{"hello": "world"}}

Per JSON mapping spec (https://developers.google.com/protocol-buffers/docs/proto3#json)

If the Any contains a value that has a special JSON mapping, it will be converted as follows: {"@type": xxx, "value": yyy}. Otherwise, the value will be converted into a JSON object, and the "@type" field will be inserted to indicate the actual data type.

Output is missing "@type" key-value. I'm going to treat dynamic message as the latter case, i.e. not having any special JSON mapping. So, above should have output

{"iany":{"@type":"ok.com/pb.Dynamic", "hello": "dynamic"}}

[cybrcodr]

Here's a description of a possible solution ...

In the following block for calling JSONPBMarshaler.MarshalJSONPB ...
https://github.com/golang/protobuf/blob/master/jsonpb/jsonpb.go#L121

if typeURL != "", need to add @type key-value into the resulting json bytes.

[cybrcodr]

Fixed in 6e4cc92