Potential name conflicts when depending on external protos about rules_proto HOT 4 CLOSED

The main issue is that skylark starlark rules do not allow one to "work" outside the package they are defined in. So, when you ctx.action.declare_file, any file you create must within that package, which has the downstream ramifications you observe. Without having reviewed the specific implementation of the native rules, I don't think they have this restriction.

Arguably the "best" way to accomplish proto compilation is via an aspect-based implementation (which may solve the aforementioned issue), but doing that in a generic way for multiple languages is not trivial.

In any case, I agree the paths for generated protos can get confusing and problematic.

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Hi @pcj:

Thanks for the response! I researched and experimented a little bit more and reached the same point (root cause and solution) you brought up. I am happy that problem is ACK'ed and the root problem is thoroughly exposed. Will work around this issue by copying .proto files around for now.

I believe that the Bazel built-in {cc,java}_proto_library rules use an aspect-based approach. This belief came from this blog post. Though that blog post (2017/02/27) was pretty old by now (2018/12/20).

I am very interested in 'doing that (the aspect way) in a generic way for multiple languages is not trivial' you mentioned. I know it could be hard and a little far fetching, but would you like to shed more light on the difficulties that you can envision?

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OK I have an initial working aspect-based implementation on the "aspect" branch. It still makes my brain hurt, and the code is in complete chaos but you're welcome to try it out.

It works well for dynamic languages like python but will make rules like cpp_proto_library implementations quite difficult.

https://github.com/stackb/rules_proto/tree/aspect

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Thanks for the response. I won't have time to try it out right at the moment. But I will keep an eye on this and try to get this to work when I get some time.

Thanks for everything. Closing for now.

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