Hi folks,

We are using Bazel to build our application and running into trouble with "cross-compilation" of our python projects. Specifically, we are trying to set up bazel such that we can run the projects on MacOS as well as build Debian-based docker containers locally.

For reference, we are on Bazel version 7.6 and rules_python 1.6.3

I have read through #260 and the related issues, as well as the docs at:

https://rules-python.readthedocs.io/en/latest/howto/multi-platform-pypi-deps.html
https://rules-python.readthedocs.io/en/latest/pypi/download.html#bazel-downloader-and-multi-platform-wheel-hub-repository
https://rules-python.readthedocs.io/en/latest/api/rules_python/python/extensions/pip.html#pip.parse

The issue is, when building containers, the python interpreter is correctly chosen (linux aarch64) but the dependency wheels are built for MacOS.

The command we use to build the container:
bazel build //services/service:service_oci_image --platforms=@toolchains_llvm//platforms:linux-aarch64 --extra_toolchains=@llvm_toolchain_cc//:cc-toolchain-aarch64-linux

Load it:
bazel run //:service_load --platforms=@toolchains_llvm//platforms:linux-aarch64

And finally run it:
docker run service:latest

This fails due to the wrong wheel being chosen (in the container):
find /services/service -type f -name "*_pydantic_core*.so"
/services/service/service_bin.runfiles/rules_python~~pip~pip_312_pydantic_core/site-packages/pydantic_core/_pydantic_core.cpython-312-darwin.so

Here's what we do:

MODULE.bazel

PYTHON_VERSION = "3.12.11"
pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
pip.parse(
 hub_name = "pip",
 python_version = PYTHON_VERSION,
 requirements_lock = "//:requirements_lock.txt",
 requirements_by_platform = {
 "//:requirements_lock.txt": "linux_aarch64",
 "//:requirements_lock_darwin.txt": "osx_x86_64",
 },
)
use_repo(pip, "pip")

BUILD.bazel

oci_load(
 name = "service_load",
 image = "//services/service:service_oci_image",
 repo_tags = ["service:latest"],
 visibility = ["//visibility:public"],
)

services/service/BUILD.bazel

py_binary(
 name = "service_bin",
 srcs = ["__main__.py"],
 imports = ["../.."],
 main = "__main__.py",
 visibility = ["//:__subpackages__"],
 deps = [
		...
 "@pip//pydantic",
 ],
)
PACKAGES = [
# 
]
py_oci_image(
 name = "service_oci_image",
 base = "@debian12",
 binary = ":service_bin",
 entrypoint = [
 "/bin/bash",
 "/services/service/service_bin",
 ],
 tars = select(
 {
 "@platforms//cpu:arm64": ["%s/arm64" % package for package in PACKAGES],
 "@platforms//cpu:aarch64": ["%s/arm64" % package for package in PACKAGES],
 },
 ),
 visibility = ["//:__subpackages__"],
)

Our requirements files are compiled on the respective platforms and contain package hashes.

Is there an intermediate solution until #260 is complete that we can use?

Additionally, it would be nice if the solution can play well with gazelle.

Thank you!