Upstreamed fix from nix, see patch here:
https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/python-modules/setuptools/setuptools-distutils-C%2B%2B.patch

… on PyPy.

…ject and adjust expectations in tests.

…pathlib Path).

Remove extra quotes from litteral strings

This reverts commit d3e5de0.

Starting with b42197c UnixCCompiler got some improved support
for cygwin which made the doctest fail.

The doctest is hard to read as is, and adding more platform specific exceptions
wouldn't help, so just convert to a normal test and special case cygwin to make
the test pass there again.

Mingw32CCompiler() checks that the default compiler isn't cygwin,
so it can't be used under cygwin, so skip it there.

Fix cygwin CI job

Fix PERF401 errors.

…ta file.

Prior to 3.11, singledispatch[method] doesn't know about unions.

… with upstream.

…mum compatibility with other libraries.

… backslashes.

…Instead, trailing slashes are stripped just as they are with pathlib.Path.

Ref pypa/distutils#272 (comment).

…lls `.as_posix()` on it.

This change will have the unintended effect of adding support for backslashes on Windows. Maybe that's fine, or maybe it should be prohibited.

…nkeypatching os.path.

…rive-relative absolute on Windows.

Test for convert_path no longer runs on all operating systems as it's too difficult (impossible) to monkeypatch PurePath reliably.

…n a platform-sensitive way. Should fix failures on mingw.

…files

Allow path objects for data-files

ENH: Extension should be able to accept PathLike sources objects

Otherwise the test fails if arguments are passed to pytest, for example --no-cov:

FAILED distutils/tests/test_dist.py::TestDistributionBehavior::test_venv_install_options -
      distutils.errors.DistutilsArgError: option --no-cov not recognized

…fault compiler

The tests currently assume everywhere that there is only one compiler per platform,
and while it would be possible to parametrize all the tests it would make things more
complex and we'd also have to decide which compiler is required for running the tests and
which one is optional etc.

To avoid all this introduce a DISTUTILS_TEST_DEFAULT_COMPILER env var which can be used
to override the default compiler type for the whole test run. This keeps the tests as is
and makes sure all tests run against the alternative compiler. Also add it to pass_env
for tox, so it gets passed to pytest, if set.

The added CI job installs an ucrt targeting GCC via MSYS2, and forces the MSVC CPython
to use it via DISTUTILS_TEST_DEFAULT_COMPILER=mingw32.

This was added back in the day to make mingw use the same CRT as CPython
(https://bugs.python.org/issue870382), but at least with newer mingw-w64 and
ucrt switching the CRT at "runtime" isn't supported anymore. To build a
compatible extension you have to use a ucrt mingw-w64 build, so things match
up and link against the same CRT.

CPython 3.5+ uses ucrt (see https://wiki.python.org/moin/WindowsCompilers), so
anything besides that is no longer relevant, which only leaves vcruntime140.

Since it's not clear what linking against vcruntime140 solves, and there have
been reports of it needing to be patched out:

* #4101
* pypa/distutils#204 (comment)

let's just make it return nothing. Keep get_msvcr() around for now to avoid breaking
code which patched it.

Fixes #204

Its last use in cygwinccompiler was just removed.

…ars.

…_add_flags logic.

Reduces cyclomatic complexity so it passes QA checks.

…ARED is unset.

Distutils C++ support

…nv_install_options

venv_install_options: add missing clear_argv fixture

…on-mingw-variant2

mingw: make get_msvcr() a noop + add a CI job testing MSVC Python with GCC