export well known protos

[smparkes]

When we run protoc from within bazel, we need access to the well known protos, e.g., Any, so that protoc can include them.

[xfxyjwf]

Are you using genrule to invoke protoc? Why not use the _proto_library rule implemented in protobuf.bzl?

[liujisi]

LGTM

[smparkes]

This is actually part of making protoc work for me from bazel. I have my own skylark extension to run protoc (handles, among other things, java) but will eventually try to submit a PR (if you'd like it/when I get a chance to clean it up.)

The current protoc defined in protobuf.bzl doesn't include access to the well known protos, e.g., Any, so trying to bazel run/bazel-bin won't work:

❯❯❯ ./bazel-bin/protoc --cpp_out=. foo.proto
google/protobuf/any.proto: File not found.
foo.proto: Import "google/protobuf/any.proto" was not found or had errors.
foo.proto:7:12: "google.protobuf.Any" is not defined.

Step one (I think ...) is to tell bazel these files are used elsewhere, e.g., by protoc. That's what I added the filegroup for: that way, should they change, the output of protoc is invalidated.

The second step is to pass them to protoc when it gets run. I've hacked that in my extension but am not happy with it: it adds a -I flag when it runs protoc but it to src which is less than great so I want to (eventually) improve that.

[xfxyjwf]

LGTM

Thanks for the explanation.