Never use the pkg_resources backend on python 3.13+

Author: sbidoul

news/13010.removal.rst

@@ -0,0 +1,2 @@
+On python 3.13+, the ``pkg_resources`` metadata backend is not used anymore,
+and pip does not attempt to detect installed ``.egg`` distributions.

src/pip/_internal/metadata/__init__.py

@@ -30,16 +30,19 @@ def _should_use_importlib_metadata() -> bool:
     """Whether to use the ``importlib.metadata`` or ``pkg_resources`` backend.
 
     By default, pip uses ``importlib.metadata`` on Python 3.11+, and
-    ``pkg_resourcess`` otherwise. This can be overridden by a couple of ways:
+    ``pkg_resourcess`` On Python <3.13. Up to Python 3.12, This can be
+    overridden by a couple of ways:
 
     * If environment variable ``_PIP_USE_IMPORTLIB_METADATA`` is set, it
       dictates whether ``importlib.metadata`` is used, regardless of Python
       version.
-    * On Python 3.11+, Python distributors can patch ``importlib.metadata``
-      to add a global constant ``_PIP_USE_IMPORTLIB_METADATA = False``. This
-      makes pip use ``pkg_resources`` (unless the user set the aforementioned
+    * On Python 3.11+, Python distributors can patch ``importlib.metadata`` to
+      add a global constant ``_PIP_USE_IMPORTLIB_METADATA = False``. This makes
+      pip use ``pkg_resources`` (unless the user set the aforementioned
       environment variable to *True*).
     """
+    if sys.version_info >= (3, 13):
+        return True
     with contextlib.suppress(KeyError, ValueError):
         return bool(strtobool(os.environ["_PIP_USE_IMPORTLIB_METADATA"]))
     if sys.version_info < (3, 11):

src/pip/_internal/metadata/importlib/_envs.py

@@ -173,9 +173,10 @@ def _iter_distributions(self) -> Iterator[BaseDistribution]:
         finder = _DistributionFinder()
         for location in self._paths:
             yield from finder.find(location)
-            for dist in finder.find_eggs(location):
-                _emit_egg_deprecation(dist.location)
-                yield dist
+            if sys.version_info < (3, 13):
+                for dist in finder.find_eggs(location):
+                    _emit_egg_deprecation(dist.location)
+                    yield dist
             # This must go last because that's how pkg_resources tie-breaks.
             yield from finder.find_linked(location)
 

tests/functional/test_uninstall.py

@@ -628,6 +628,10 @@ def test_uninstall_with_symlink(
     assert symlink_target.stat().st_mode == st_mode
 
 
+@pytest.mark.skipif(
+    "sys.version_info >= (3, 13)",
+    reason="Uninstall of .egg distributions not supported in Python 3.13+",
+)
 def test_uninstall_setuptools_develop_install(
     script: PipTestEnvironment, data: TestData
 ) -> None: