bpo-46246: add missing __slots__ to importlib.metadata.DeprecatedList (GH-30452)

Confirmed with @jaraco that this indeed needs a fix.

A question that came up while I was digging into the code: I think `SelectableGroups` could similarly use `__slots__ = ()`, since its purpose seems only for convenience around `dict`, not to have attributes of its own.

Automerge-Triggered-By: GH:jaraco
(cherry picked from commit dd76b3f7d332dd6eced5cbc2ad2adfc397700b3d)

Co-authored-by: Arie Bovenberg <a.c.bovenberg@gmail.com>

diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
index 33ce1b6b569640c6890dc0170d872938c4030acc..c7462f31c7a0f293d5f49b22ebd65f524e32cf9a 100644 (file)
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -236,6 +236,8 @@ class DeprecatedList(list):
     1
     """
 
+    __slots__ = ()
+
     _warn = functools.partial(
         warnings.warn,
         "EntryPoints list interface is deprecated. Cast to list if needed.",

diff --git a/Lib/test/test_importlib/test_metadata_api.py b/Lib/test/test_importlib/test_metadata_api.py
index 4a45312e31cd587ec6499d5880f8143990ba35ac..0890d6cb72e88ac6e862929e79883be608c85481 100644 (file)
--- a/Lib/test/test_importlib/test_metadata_api.py
+++ b/Lib/test/test_importlib/test_metadata_api.py
@@ -172,6 +172,11 @@ class APITests(
             entry_points().get('entries', 'default') == entry_points()['entries']
             entry_points().get('missing', ()) == ()
 
+    def test_entry_points_allows_no_attributes(self):
+        ep = entry_points().select(group='entries', name='main')
+        with self.assertRaises(AttributeError):
+            ep.foo = 4
+
     def test_metadata_for_this_package(self):
         md = metadata('egginfo-pkg')
         assert md['author'] == 'Steven Ma'

diff --git a/Misc/NEWS.d/next/Library/2022-01-07-13-27-53.bpo-46246.CTLx32.rst b/Misc/NEWS.d/next/Library/2022-01-07-13-27-53.bpo-46246.CTLx32.rst
new file mode 100644 (file)
index 0000000..4850171
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-01-07-13-27-53.bpo-46246.CTLx32.rst
@@ -0,0 +1,2 @@
+Add missing ``__slots__`` to ``importlib.metadata.DeprecatedList``. Patch by
+Arie Bovenberg.