Update jsonpb to handle Map, Slice, Ptr nil values for EmitDefaults

[ewang]

My attempt at making the Map, Slice, nil Ptr type marshaling match the proto3 JSON spec.

Fixes: #323

Related PRs:
#232
#287

[cybrcodr]

Sorry for the delayed review. I just got assigned to start looking at these. Changes look good. Please to sync to head first and I'll approve.

Thanks.

[ewang]

@cybrcodr Rebased

[cybrcodr]

Thanks!

[tamird]

@cybrcodr @ewang this commit seems to have the unfortunate effect of (*string)(nil) becoming &"" when marshalled and unmarshalled. Specifically, we have this proto:

syntax = "proto2";
package cockroach.build;
option go_package = "build";

import "gogoproto/gogo.proto";

message Info {
  optional string go_version = 1 [(gogoproto.nullable) = false];
  optional string tag = 2 [(gogoproto.nullable) = false];
  optional string time = 3 [(gogoproto.nullable) = false];
  optional string revision = 4 [(gogoproto.nullable) = false];
  optional string cgo_compiler = 5 [(gogoproto.nullable) = false];
  optional string platform = 6 [(gogoproto.nullable) = false];
  optional string distribution = 7 [(gogoproto.nullable) = false];
  optional string type = 8 [(gogoproto.nullable) = false];

  optional string dependencies = 10000;
}

Here's my test case:

func TestProtobuf(t *testing.T) {
	var b bytes.Buffer

	var in build.Info
	if err := (&jsonpb.Marshaler{EmitDefaults: true}).Marshal(&b, &in); err != nil {
		t.Fatal(err)
	}
	var out build.Info
	if err := jsonpb.Unmarshal(&b, &out); err != nil {
		t.Fatal(err)
	}
	if out != in {
		t.Error(pretty.Diff(out, in))
	}
}

and it fails with

--- FAIL: TestProtobuf (0.00s)
	status_test.go:140: [Dependencies: &"" != nil]

[cybrcodr]

Can you try out head version? In #394, deserializing "null" for all message types except wkt ValueType should translate to nil value.

I also tried it out with a simplified example from yours.

syntax = "proto2";
option go_package = "optstring/pb";

message Info {
  optional string dependencies = 10000;
}

package main

import (
        "bytes"
        "fmt"
        "log"

        "optstring/pb"

        "github.com/golang/protobuf/jsonpb"
)

func main() {
        b := &bytes.Buffer{}
        p1 := &pb.Info{}
        fmt.Printf("before serializing %#+v\n", p1)
        m := jsonpb.Marshaler{EmitDefaults: true}
        if err := m.Marshal(b, p1); err != nil {
                log.Fatal(err)
        }
        fmt.Printf("serialized json: %s\n", b.String())

        p2 := &pb.Info{}
        if err := jsonpb.Unmarshal(b, p2); err != nil {
                log.Fatal(err)
        }
        fmt.Printf("deserialized into %#+v\n", p2)
        if p2.Dependencies == nil {
                fmt.Println("is nil!!!")
        }
}

Output...

before serializing &pb.Info{Dependencies:(*string)(nil), XXX_unrecognized:[]uint8(nil)}
serialized json: {"dependencies":null}
deserialized into &pb.Info{Dependencies:(*string)(nil), XXX_unrecognized:[]uint8(nil)}
is nil!!!

Let me know if head doesn't work out for you.

[tamird]

Thanks! We're using gogo/protobuf, so I've filed gogo/protobuf#319. I'll give it a shot once #394 is brought over.