License_files improvements

[cdce8p]

Summary of changes

• Add support for glob patterns in license_file and license_files options.
• Add default patterns if neither is specified to match behavior of bdist_wheel.
  https://wheel.readthedocs.io/en/stable/user_guide.html#including-license-files-in-the-generated-wheel-file
• Added deprecation warning if license_file file is used. license_files is a full replacement.
• Added additional documentation for the license_files option.

The implementation is similar to the one used by wheel: wheel/bdist_wheel.py

Closes #2616

Pull Request Checklist

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

[jaraco]

In my experience, MANIFEST.in only affects the sdist. Can you confirm that exclude in MANIFEST.in with LICENSE present has the same effect as not specifying a license on older Setuptools?

[cdce8p]

I'm not exactly sure what you mean. AFAIK the change itself will only the sdist command. bdist_wheel will use the license_file and license_files fields or the default patterns. Therefore it's probably not wise to exclude a license file in the MANIFEST.in to begin with. But in case you only care about the source dist, any exclude does have president over a matched license file. There are two existing test cases that cover it.
I'm going to remove the last sentence, since it's probably more confusing than helpful especially to beginners.

setuptools/setuptools/tests/test_egg_info.py

Lines 637 to 655 in 7432981

	({
	'setup.cfg': DALS("""
	[metadata]
	license_files = LICENSE
	"""),
	'MANIFEST.in': "exclude LICENSE",
	'LICENSE': "Test license"
	}, [], ['LICENSE']), # license file is manually excluded
	({
	'setup.cfg': DALS("""
	[metadata]
	license_files =
	LICENSE-ABC
	LICENSE-XYZ
	"""),
	'MANIFEST.in': "exclude LICENSE-XYZ",
	'LICENSE-ABC': "ABC license",
	'LICENSE-XYZ': "XYZ license"
	}, ['LICENSE-ABC'], ['LICENSE-XYZ']), # subset is manually excluded

[jaraco]

Nice work. Thorough and clean. Just a couple of nitpicks or requests for additional information, but it's basically ready to go.

[cdce8p]

Thanks for the review! I did a rebase to get rid of the test fix and pushed a small commit to address the comments: 608c376

As a side note here, I was thinking about if it would be possible to do these steps even earlier. PEP 639, currently still a draft but quite far along, would add the License-File (multiple) field to the package metadata, Link. To support that use case, the pattern matching for license files probably needs to happen during the egg-info command. What is your opinion regarding this? Could you give my a pointer on how to best approach it?

[jaraco]

What is your opinion regarding this? Could you give my a pointer on how to best approach it?

I'm in favor of exposing the license text(s) in metadata. I don't have any active context on such an effort. I don't even know where license files are presented currently.

I'd start out by filing a bug and describe the problem and start exploring possible solutions. I'd use that forum to examine the code and current behavior and devise a transition to a solution that meets the need. I'd identify projects and people that would be affected by such a change and gather their feedback.