[Feature Request] Public interface for _msvccompiler._get_vc_env

[ozanMSFT]

pytorch's repository is using an import of setuptools / distutil.

https://github.com/pytorch/pytorch/blob/main/tools/build_pytorch_libs.py#L17-L25

def _get_vc_env(vc_arch: str) -> dict[str, str]:
    try:
        from setuptools import distutils  # type: ignore[import]

        return distutils._msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]
    except AttributeError:
        from setuptools._distutils import _msvccompiler  # type: ignore[import]

        return _msvccompiler._get_vc_env(vc_arch)  # type: ignore[no-any-return]

However, its location/implementation is being changed and causing the errors as follows:

AttributeError: module 'distutils._msvccompiler' has no attribute '_get_vc_env'

Example issues:
pypa/setuptools#4874
pytorch/pytorch#148877
pytorch/pytorch#141319

---

Could you please open a reliable public interface for _get_vc_env , so pytorch 's repository could be updated to use that import for the future versions?

[jaraco]

Can you tell me more about the use-case(s) for this function? Does the setuptools.msvc module provide the necessary behaviors? Is _get_vc_env used to extract the inner details of the compiler or is it used simply to pass through to invocations of build tools?

[ozanMSFT]

Based on use case which I've provided in the description for the PyTorch:

It is being used to get necessary environment variables of MSVC as dictionary and it is being passed to cmake for further process.

As far as I see, setuptools.msvc module doesn't have a function to return environment variables as dictionary as _msvccompiler._get_vc_env(vc_arch) does.