Hi Pythonistas,
%pyproject_save_files automatically handles marking license files with %license when a build backend installs them into a package's dist-info directory and the License-File header is specified in the METADATA file. Currently, only setuptools and hatchling meet this criteria. Notably, poetry and flit do not support this. They will install license texts into the dist-info directory, but they do not add the License-File metadata. The License-File tag is not standardized, and discussion on PEP 639 which defines this standard has stalled. I believe relying on this feature is a problem, as if a project changes build systems or some other config and a packager doesn't realize, suddenly the license file won't be marked with %license or even worse, not installed at all. Since the pyproject macros read the build backend from pyproject.toml without packagers having to manually specify anything (which is generally great!), this situation seems likely to occur.
Until these issues are resolved, I propose banning this in Fedora and requiring packagers to manually mark files with %license or at least adding a large warning to the Packaging Guidelines. It can be similar to the `'*' +auto` flags which are used by pyp2spec for automatic PyPI builds in Copr but not allowed in Fedora proper. What do y'all think? Am I missing something?