Can't compile with Proto3 optional fields

[alancleary]

I see that support for Proto3 optional fields was added in pull #884, which was included in release 1.2.1. However, when I try to generate TypeScript files from a protobuf file containing optional fields I receive an error:

helloworld.proto: is a proto3 file that contains optional fields, but code
generator --js_out hasn't been updated to support optional fields in proto3.
Please ask the owner of this code generator to support proto3 optional.

I'm using protoc version 3.12.4 and grpc-web version 1.2.1.

Here's the protoc command:

$ protoc -I=. helloworld.proto --experimental_allow_proto3_optional \
  --js_out=import_style=commonjs,binary:. \
  --grpc-web_out=import_style=typescript,mode=grpcwebtext:.

And here's helloworld.proto:

syntax = "proto3";

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
}

message HelloRequest {
  optional string name = 1;
}

message HelloReply {
  string message = 1;
}

Hopefully this is an error on my part, otherwise I guess this could be considered a feature request. Any thoughts on what might be happening here?

[stanley-cheung]

I believe for --js_out, which is the part of the standard protoc distribution (not a grpc-web distribution), that part of the plugin has only been updated since version 3.13.0, but I am not sure. In any case, please check with the protocolbuffers repo for that particular plugin.

[alancleary]

Thanks for the quick reply, @stanley-cheung. I didn't realize --js_out is part of the protoc distribution. I upgraded protoc to version 3.13.0 and indeed it compiled with Proto3 optional fields. Cheers!