[Python-checkins] gh-93910: [Enum] restore member.member restriction while keeping performance boost (GH-94913)

[ethanfurman]

https://github.com/python/cpython/commit/c20186c3972ff38577c4c5e32ca86748210983d2
commit: c20186c3972ff38577c4c5e32ca86748210983d2
branch: main
author: Ethan Furman <ethan at stoneleaf.us>
committer: ethanfurman <ethan at stoneleaf.us>
date: 2022-07-16T18:13:57-07:00
summary:

gh-93910: [Enum] restore member.member restriction while keeping performance boost (GH-94913)

files:
M Lib/enum.py
M Lib/test/test_enum.py

diff --git a/Lib/enum.py b/Lib/enum.py
index 652878ce1e1df..a4f1f09adae01 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -1101,6 +1101,14 @@ def __new__(cls, value):
     def __init__(self, *args, **kwds):
         pass
 
+    def __getattribute__(self, name):
+        self_dict = super().__getattribute__('__dict__')
+        cls = super().__getattribute__('__class__')
+        value = super().__getattribute__(name)
+        if isinstance(value, cls) and name not in self_dict and name in self._member_names_:
+            raise AttributeError("<enum '%s'> member has no attribute %r" % (cls.__name__, name))
+        return super().__getattribute__(name)
+
     def _generate_next_value_(name, start, count, last_values):
         """
         Generate the next value when not given.
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index aec18c79f7249..87d7c725014e3 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -2646,7 +2646,6 @@ class Private(Enum):
         self.assertEqual(Private._Private__corporal, 'Radar')
         self.assertEqual(Private._Private__major_, 'Hoolihan')
 
-    @unittest.skip("Accessing all values retained for performance reasons, see GH-93910")
     def test_exception_for_member_from_member_access(self):
         with self.assertRaisesRegex(AttributeError, "<enum .Di.> member has no attribute .NO."):
             class Di(Enum):
@@ -2654,6 +2653,12 @@ class Di(Enum):
                 NO = 0
             nope = Di.YES.NO
 
+    def test_no_exception_for_overridden_member_from_member_access(self):
+        class Di(Enum):
+            YES = 1
+            NO = 0
+        Di.YES.NO = Di.NO
+        nope = Di.YES.NO
 
     def test_dynamic_members_with_static_methods(self):
         #