Python 3.8 wheels fail to install on Windows

[chrahunt]

Environment

• pip version: 19.2.2
• Python version: 3.8b3
• OS: Windows 10

Description

As described by @rdb in pypa/packaging#180:

On Windows, pip fails to install binary wheels with the following error:

ERROR: mypackage-1.0.0-cp38-cp38-win_amd64.whl is not a supported wheel on this platform.

Expected behavior

pip installs wheels with Python 3.8.

How to Reproduce

:: Goes through (but fails because it is not a zip) even though the ABI tag cp38m is not valid
echo > project-0.1.0-cp38-cp38m-win_amd64.whl
pip install ./project-0.1.0-cp38-cp38m-win_amd64.whl
:: Fails to consider this file even though it has the valid cp38 ABI tag
echo > project-0.1.0-cp38-cp38-win_amd64.whl
pip install ./project-0.1.0-cp38-cp38-win_amd64.whl

Output

(.venv) C:\Users\User\Desktop\test>echo > project-0.1.0-cp38-cp38m-win_amd64.whl

(.venv) C:\Users\User\Desktop\test>pip install ./project-0.1.0-cp38-cp38m-win_amd64.whl
Processing c:\users\user\desktop\test\project-0.1.0-cp38-cp38m-win_amd64.whl
ERROR: Exception:
Traceback (most recent call last):
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\cli\base_command.py", line 188, in main
    status = self.run(options, args)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\commands\install.py", line 345, in run
    resolver.resolve(requirement_set)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\legacy_resolve.py", line 196, in resolve
    self._resolve_one(requirement_set, req)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\legacy_resolve.py", line 359, in _resolve_one
    abstract_dist = self._get_abstract_dist_for(req_to_install)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\legacy_resolve.py", line 305, in _get_abstract_dist_for
    abstract_dist = self.preparer.prepare_linked_requirement(
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\operations\prepare.py", line 195, in prepare_linked_requirement
    unpack_url(
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\download.py", line 1051, in unpack_url
    unpack_file_url(link, location, download_dir, hashes=hashes)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\download.py", line 985, in unpack_file_url
    unpack_file(from_path, location, content_type, link)
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\utils\misc.py", line 732, in unpack_file
    unzip_file(
  File "c:\users\user\desktop\test\.venv\lib\site-packages\pip\_internal\utils\misc.py", line 612, in unzip_file
    zip = zipfile.ZipFile(zipfp, allowZip64=True)
  File "C:\opt\python.3.8.0-b3\tools\lib\zipfile.py", line 1232, in __init__
    self._RealGetContents()
  File "C:\opt\python.3.8.0-b3\tools\lib\zipfile.py", line 1299, in _RealGetContents
    raise BadZipFile("File is not a zip file")
zipfile.BadZipFile: File is not a zip file

(.venv) C:\Users\User\Desktop\test>echo > project-0.1.0-cp38-cp38-win_amd64.whl

(.venv) C:\Users\User\Desktop\test>pip install ./project-0.1.0-cp38-cp38-win_amd64.whl
ERROR: project-0.1.0-cp38-cp38-win_amd64.whl is not a supported wheel on this platform.

Details

In pep425flags here when constructing our ABI tag, we check:

1. if sysconfig.get_config_var('SOABI'), then use that
2. otherwise, if sysconfig.get_config_var('WITH_PYMALLOC'), add m
3. otherwise, if we're running CPython, add m

On Windows, neither SOABI or WITH_PYMALLOC are defined, so then we unconditionally add m to our required ABI tags for CPython. But this is incorrect since m was removed from the ABI as part of 3.8 per bpo-36707.

On macOS and Linux we already have the correct tag since SOABI is defined.

See also

• Don't append "m" ABI flag in Python 3.8 #6874
• Removal of 'm' flag from tag in Python 3.8 packaging#180
• Don't append "m" ABI flag in Python 3.8 wheel#303

[chrahunt]

Closed by #6874.