Support for optional fields

[wim07101993]

When declaring a field as optional the protoc-gen-go compiler exits with the error: protos/test.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.

Is this still experimental? It was added in v1.22.0 almost 4 years ago.

command: protoc --go_out "generated" protos/test.proto

proto file:

syntax = "proto3";

package option_test;

option go_package = "grpc_test";

message OptionMessage {
  optional int32 value = 1;
}

$ protoc --version
libprotoc 3.12.4

$ protoc-gen-go --version
protoc-gen-go v1.28.1

[neild]

That error message is printed by protoc, not the Go code generator.

I believe the most recent version of protoc is 25.3:
https://github.com/protocolbuffers/protobuf/releases

[wim07101993]

Indeed, the version I had came from the Ubuntu package manager but hasn't been updated since 2020... The latest releases from github seem to work.