Raise an error on invalid egg fragments

[ichard26]

We deprecated anything that isn't a bare project name in an egg fragment in #11567. It's scheduled for removal in pip 25.0. Let's make this an error.

pip/src/pip/_internal/models/link.py

Lines 459 to 475 in 1452429

	def _egg_fragment(self) -> Optional[str]:
	match = self._egg_fragment_re.search(self._url)
	if not match:
	return None
	# An egg fragment looks like a PEP 508 project name, along with
	# an optional extras specifier. Anything else is invalid.
	project_name = match.group(1)
	if not self._project_name_re.match(project_name):
	deprecated(
	reason=f"{self} contains an egg fragment with a non-PEP 508 name",
	replacement="to use the req @ url syntax, and remove the egg fragment",
	gone_in="25.0",
	issue=11617,
	)
	return project_name

cc @woodruffw

[ichard26]

Hmm, editable VCS installs don't support the direct URL syntax. This means the egg fragment is the only supported way to request an extra for VCS URLs. We'd need to revive #9471 before raising an error.

It's probably best to punt this to a later release.

[notatallshaw]

I think uv already supports the syntax "mypackage[extra] @ {VCS_URL}", but I've never looked at how feasible this is in pip or if it's been tried before.