Proto3 repeated field not packed by default

[kitak]

Message definitions

proto3_test.proto:

syntax = "proto3";

package test;

message Test3Int32RepDefault {
    repeated int32 repeated_int32 = 1;
}

message Test3Int32RepPackedTrue {
    repeated int32 repeated_int32 = 1 [packed = true];
}

Compiled via:

$ protoc --version
libprotoc 3.6.1
$ protoc --dart_out=grpc:. ./proto3_test.proto

Serialization Code and results

import './proto3_test.pb.dart';
import 'dart:io';

Future<void> main() async {
  final repDefault = Test3Int32RepDefault()
    ..repeatedInt32.addAll([2,3,5]);
  final file = File("./rep_default");
  file.writeAsBytes(repDefault.writeToBuffer());

  final packedTrue = Test3Int32RepPackedTrue()
    ..repeatedInt32.addAll([2,3,5]);
  final file2 = File("./packed_true");
  file2.writeAsBytes(packedTrue.writeToBuffer());
}

$ hexdump rep_default
0000000 08 02 08 03 08 05
0000006
$ hexdump packed_true
0000000 0a 03 02 03 05
0000005

The repeated field with default packed setting compiles to a non-packed field although it should be packed by default.

[shekohex]

I hit this bug today between my server (in Rust) which correctly packs the values by default as per protobuf3 spec, and dart does not do that by default!

I ended up explicitly adding [packed = true] to the fields as a workaround for now!