Using FieldOptions in both Go and C++

[hochhaus]

I have a *.proto file which uses FieldOptions.

syntax = "proto2";

import "google/protobuf/descriptor.proto";

enum Int64Encoding {
  JS_DEFAULT = 0;
  JS_NUMBER = 1;
}

extend google.protobuf.FieldOptions {
  optional Int64Encoding jstype = 50001;
}

I wish to use this protocol buffer from both C++ and go.

However, protoc-gen-go generates the following import path in the *.pb.go file:

import google_protobuf "google/protobuf"

However, in the go protobuf implementation descriptor.pb.go lives at a different path location. It seems to me that possibly protoc-gen-go should be special cased to write the import as:

import google_protobuf "github.com/golang/protobuf/protoc-gen-go/descriptor"

Does this seem like reasonable behavior for descriptor.proto imports? If so, I will send a patch set. If not, I can easily work around this in our build layer.

[dsymonds]

The Go code generator doesn't treat any import paths as particularly special (that might change as part of #50), so the "google/protobuf" import path is simply a mechanical transformation. You can use the M parameter to declare what the import path should be.

The descriptor package in this repo is really only meant to be for protoc-gen-go's use.

[zeroZshadow]

Sorry to ask after closing, but how does the M parameter work?

[hochhaus]

You can include "M" in your --go_out flag in the following form:

protoc --go_out=M<.proto>=<package>:. <proto>

So if you want to rewrite descriptor.proto (as per my original question), that would look like:

protoc --go_out=Mgoogle/protobuf/descriptor.proto=github.com/golang/protobuf/protoc-gen-go/descriptor:. <file.proto>

You can also include multiple "M" arguments as a comma separated list.

[Antonboom]

@hochhaus

Where can I read more about this "M" option?