Provide support for dash-separated keys in setup.cfg, warns for future incompatibility of certain keys

[melissa-kun-li]

Summary of changes

Closes #1608

This change will preserve dashes in the keys of setup.cfg. This will also implement a compatibility method which will warn users through UserWarning if they use an alias involving a dash which should technically be underscore separated (e.g. using author-email instead of author_email). After warning for these types of aliases, dash to underscore conversion will be performed for compatibility, but in the future Setuptools will no longer support the alias conversion.

Pull Request Checklist

• Changes have tests
• News fragment added in changelog.d/.
  (See documentation for details)

[jaraco]

This is really great. Nice work on creating tests for the warning as well as for the condition that led to this change. Also nice work on the guidance. I'm a little concerned about the explicit list of options. Let's mull over the tradeoffs there and we're good to go.

[jaraco]

Looks great. Well done!

[hugovk]

Hi! I checked https://setuptools.readthedocs.io/en/latest/history.html#v54-1-0 but I wasn't entirely clear: is this meant to warn for all keys using hyphens in setup.cfg? For example, I see warnings for these Flake8 options:

$ cat setup.cfg
[flake8]
extend-ignore = E203
max-line-length = 88

[isort]
profile = black

[tool:pytest]
addopts = -ra --color=yes
testpaths = Tests
$ python setup.py --version
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'extend-ignore' will not be supported in future versions. Please use the underscore name 'extend_ignore' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'max-line-length' will not be supported in future versions. Please use the underscore name 'max_line_length' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'extend-ignore' will not be supported in future versions. Please use the underscore name 'extend_ignore' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'max-line-length' will not be supported in future versions. Please use the underscore name 'max_line_length' instead
  warnings.warn(
8.2.0.dev0

Flake8 themselves say both underscores and hyphens are fine in setup.cfg:

https://flake8.pycqa.org/en/latest/user/configuration.html#project-configuration

Thanks!

[melissa-kun-li]

@hugovk
Hi! So prior to v54.1.0, setup.cfg read hyphens as underscores internally which is why flake8 said that you can use either hyphens or underscores because it was being converted to underscores in the background anyway. However this caused bugs for users who needed dashes to be preserved in setup.cfg. The recent warning is to warn for future deprecation of dashes in keys of setup.cfg for those keys which should actually be underscores. So the flake8 documentation was right before, but maybe now we should let them know so they can update it. edited from what Jason said below, I'll work on a fix so it doesn't warn for flake8 and others :)

@jaraco

[jaraco]

Oh, this was a case I hadn't considered during the review. I had expected it would only apply to sections that setuptools is using.

The setup.cfg file serves as a home for many projects outside the scope of distutils/setuptools. In that case, Setuptools probably shouldn't be as opinionated about the format of the keys. I'd like to avoid other projects needing to mirror this change.

I believe we should come up with a patch to avoid these warnings. I'll convert Hugo's comment to an issue. @melissa-kun-li Would you be interested in working on the patch? In this case, I'd say a test is optional. Use misc for the changelog.

[melissa-kun-li]

@jaraco Sure! I'll work on a fix, I have an idea in mind