What is the proper way of offering targets with a fixed toolchain for other bazel workspaces?

[lucasmuna]

Hello,

I'm currently wondering what is the proper way of offering a target (py_binary for example) with a fixed toolchain for another bazel workspace.

Problematic

We could think of two workspaces base and child.

base would offer @base//:print_version target that is a py_binary loaded from load("@base_python//:defs.bzl", "py_binary").

@base_python would come from something like python_register_toolchains(name = "base_python", python_version = "3.9",.

Now, it works as expected inside base, but, if a child bazel workspace loads base, things gets complicated.

Main reason is because I don't control child rules_python version and its toolchains.

Minimal reproduction

I built an example here: https://github.com/lucasmuna/rules_python_offer_toolchain/

What I tried

1. Add the --extra_toolchains flag aiming something like @base_python_toolchains//:x86_64-unknown-linux-gnu_toolchain;
2. Customize base rules_python name (this also solves an older child rules_python version not having some newer APIs but leads to another issues);
3. Make the offered target load py_binary directly from @base_python//:defs.bzl.

Some solutions seems to works for a certain setup some for another but none of those were generic enough.

Maybe I'm missing something or maybe I'm not even supposed to follow this path.

I also had some other ideas like:

• I just say my python code is compatible with X Y Z;
• or I create and offer my own toolchains.

Any ideas are welcomed :)