Gathering transitive prebuilt_python_library dependencies

[Ralith]

I want to write a rule to package a Blender extension. Such packages are a zip archive of:

• First-party Python code
• Third-party dependencies in wheel form, exactly as downloaded from pypi
• A manifest file enumerating the wheels

I see PythonLibraryManifestsInterface defines many fields, which I guess are functions that return transitive sets of information about a library and its transitive dependencies? This looks like it could be used to gather all the first-party source code, though I haven't found a way to actually convert any of them to a list of paths I could pass to AnalysisActions.copied_dir. I think this is possible but I don't understand how to use transitive sets; guidance/examples would be very welcome.

More fundamentally, I don't see any fields that look like they describe all the prebuilt_python_library sources. Does such a thing exist? If not, could it be added? I believe this is useful for Python packaging in general: see applications discussed at astral-sh/uv#1681.