Protobuf and gRPC Support

[PranavSathy]

It would be awesome if there any way to support generating, compiling and linking in gRPC service definitions in Scala (using ScalaPB).

https://github.com/scalapb/ScalaPB

Is this something could be potentially incorporated into rules_scala?

[johnynek]

Yes. It could be. You could see the Twitter Scrooge rules as examples of how you might do this.

[johnynek]

@azymnis here is our protobuf/grpc issue. Can you comment here if you are working? I think we have someone at Stripe who will also chime in soon.

[azymnis]

@johnynek sure, I could pick this up this week. If anyone else has already done this though or they are close, let me know so we don't do double work

[azymnis]

@johnynek @ittaiz here's an ugly way to do this. Bundle scalapb's spbc with rules_scala: https://github.com/scalapb/ScalaPB/releases

Then we can have a protopb_library that will call spbc on all proto_library targets that it depends on. Does that sound too terrible?

FWIW this seems to be the approach that bazel has taken internally with protobuf and grpc: https://github.com/bazelbuild/bazel/blob/master/third_party/protobuf/BUILD

[johnynek]

yeah, that sounds right. I would call it scala_proto_library or something. You might want to check out:

https://github.com/bazelbuild/rules_scala/blob/master/twitter_scrooge/twitter_scrooge.bzl

to see how we did this with scrooge. To "bundle" we point to the jar (or binary if we really have to) that bazel can pull down and run.

[azymnis]

I'll start working on this today. If anyone has picked this up already please speak up

[jxm-stripe]

I'd not call my work all that close, TBH, mainly due to major unfamiliarity with bazel concepts.

[azymnis]

@jxm-stripe do you have a PR up?

[azymnis]

@johnynek @ittaiz I think we can close this, right?

[ittaiz]

indeed. again thank you for your work!
btw, you might be interested in #650