packaging.tags does not include `m` for abi tag in Python 3.7 (and below)

[chrahunt]

Environment

OS: Windows 10
Packaging version: 19.1
Python version: Python 3.7.4 (tags/v3.7.4:e09359112e, Jul 8 2019, 20:34:20) [MSC v.1916 64 bit (AMD64)], from nuget

Issue: The ABI tag for Python 3.7 in sys_tags() does not have cp37m (just cp37):

(.venv) PS C:\Users\User\Desktop> python -c 'from packaging.tags import sys_tags; print(list(sys_tags()))'
[<cp37-cp37-win_amd64 @ 2675185733256>, <cp37-abi3-win_amd64 @ 2675185848584>, <cp37-none-win_amd64 @ 2675185852360>, <cp36-abi3-win_amd64 @ 2675185868424>, <cp35-abi3-win_amd64 @ 2675185868488>, <cp34-abi3-win_amd64 @ 2675188128520>, <cp33-abi3-win_amd64 @ 2675188128776>, <cp32-abi3-win_amd64 @ 2675188129032>, <py37-none-win_amd64 @ 2675188129544>, <py3-none-win_amd64 @ 2675188154440>, <py36-none-win_amd64 @ 2675188154696>, <py35-none-win_amd64 @ 2675188154952>, <py34-none-win_amd64 @ 2675188155208>, <py33-none-win_amd64 @ 2675188155464>, <py32-none-win_amd64 @ 2675188155720>, <py31-none-win_amd64 @ 2675188155976>, <py30-none-win_amd64 @ 2675188156232>, <cp37-none-any @ 2675188129288>, <py37-none-any @ 2675185733576>, <py3-none-any @ 2675188156680>, <py36-none-any @ 2675188156936>, <py35-none-any @ 2675188157192>, <py34-none-any @ 2675188157448>, <py33-none-any @ 2675188157704>, <py32-none-any @ 2675188157960>, <py31-none-any @ 2675188158216>, <py30-none-any @ 2675188162632>]

Expected: The ABI tag for Python 3.7 should have cp37m.

It looks like we are relying strictly on either SOABI or WITH_PYMALLOC being available here, but neither are:

(.venv) PS C:\Users\User\Desktop> python -c "from sysconfig import get_config_var as c; print(c('SOABI')); print(c('WITH_PYMALLOC'))"
None
None

Related to #180.

[brettcannon]

The culprit is the comment:

packaging/packaging/tags.py

Line 84 in 6cb4ac1

# TODO: This code is simpler compared to pep425tags as CPython 2.7 didn't seem

where I mention that I left out the fallback semantics as I couldn't find a place where they were influencing results. Looks like they were still being used. 😁

Probably need to go back through https://github.com/pypa/pip/blob/0b23e2d68a7de096b75fe3ad290acd7239b6f8fa/src/pip/_internal/pep425tags.py#L110-L125 and use the fallbacks.

[brettcannon]

Comparing the tags that are produced by pip 19.2.2 and packaging.tags 19.1 on Windows 10, the ones pip has which packaging doesn't are:

1. cp3-none-any
2. cp37-cp37m-win_amd64

Under Debian on WSL:

1. cp3-none-any

So that cp37m case on Windows is the one issue (the cp3-non-any has been purposefully left out as it doesn't make sense).