Show License-Expression if present in package metadata

[befeleme]

With Core Metadata 2.4 a new field, License-Expression, has been added. If it's present, favor it over the deprecated (with PEP 639) legacy unstructured License field.

Closes: #13112

[pfmoore]

Could you add a test for the new output? Thanks.

[ichard26]

Also, it looks like CI is failing as the ubuntu-latest worker is now running Ubuntu 24.04 LTS which doesn't ship with subversion. We'll take a look when we can.

[befeleme]

Could you add a test for the new output? Thanks.

I'm trying to, but have a hard time with simulating the data - do I have to create a package with new metadata in order to make pip "install" it and then assert the output? Any pointers will be appreciated.

One more thing is, when pip itself moves to PEP 639 & setuptools supports it, this won't be true anymore:
https://github.com/pypa/pip/blob/main/tests/functional/test_show.py#L229
I may make test future-proof and assert the expected key per the version of metadata and existence of the field.
Or just wait for the moment to happen and then make a single change in the code.

[pfmoore]

I'm trying to, but have a hard time with simulating the data - do I have to create a package with new metadata in order to make pip "install" it and then assert the output? Any pointers will be appreciated.

You might have to - there's some examples in test_show.py which install a pre-built wheel and show it. See test_show_with_files_from_wheel for an example. Alternatively, you could write a unit test that just exercises print_results with artificial inputs - there's no need to get too clever here.