`packages_distributions` relies on setuptools implementation detail

[konstin]

This is a follow-up to #402.

packages_distributions reads top_level.txt to determine the names. This file isn't part of any PEP and to my knowledge only implemented by setuptools, as a historical artifact from eggs. This leads users to believe that build backends not supporting this function have a bug (astral-sh/uv#16423).

Would it be possible to update the documentation to accurately reflect that this is not a problem with some PEP 660 build backends not supplying top-level names, but that this function is generally not expected to work with editable installs at all, with the historical exception of setuptools?

(This may change with PEP 794)

importlib_metadata/importlib_metadata/__init__.py

Lines 1133 to 1134 in 95ecf2a

	def _top_level_declared(dist):
	return (dist.read_text('top_level.txt') or '').split()

[jaraco]

I'd accept a pull request to document this limitation. I would like to see some proper, formal support for a package to represent deterministically the top-level names that it exposes.