bpo-42567: [Enum] call __init_subclass__ after members are added (GH-23714)

When creating an Enum, type.__new__ calls __init_subclass__, but at that point the members have not been added.

This patch suppresses the initial call, then manually calls the ancestor __init_subclass__ before returning the new Enum class.

1 files changed, 73 insertions, 0 deletions

diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index ab4b52f..20bc5b3 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -2117,6 +2117,43 @@ class TestEnum(unittest.TestCase):
             class ThirdFailedStrEnum(StrEnum):
                 one = '1'
                 two = b'2', 'ascii', 9
+                
+    def test_init_subclass(self):
+        class MyEnum(Enum):
+            def __init_subclass__(cls, **kwds):
+                super(MyEnum, cls).__init_subclass__(**kwds)
+                self.assertFalse(cls.__dict__.get('_test', False))
+                cls._test1 = 'MyEnum'
+        #
+        class TheirEnum(MyEnum):
+            def __init_subclass__(cls, **kwds):
+                super().__init_subclass__(**kwds)
+                cls._test2 = 'TheirEnum'
+        class WhoseEnum(TheirEnum):
+            def __init_subclass__(cls, **kwds):
+                pass
+        class NoEnum(WhoseEnum):
+            ONE = 1
+        self.assertEqual(TheirEnum.__dict__['_test1'], 'MyEnum')
+        self.assertEqual(WhoseEnum.__dict__['_test1'], 'MyEnum')
+        self.assertEqual(WhoseEnum.__dict__['_test2'], 'TheirEnum')
+        self.assertFalse(NoEnum.__dict__.get('_test1', False))
+        self.assertFalse(NoEnum.__dict__.get('_test2', False))
+        #
+        class OurEnum(MyEnum):
+            def __init_subclass__(cls, **kwds):
+                cls._test2 = 'OurEnum'
+        class WhereEnum(OurEnum):
+            def __init_subclass__(cls, **kwds):
+                pass
+        class NeverEnum(WhereEnum):
+            ONE = 'one'
+        self.assertEqual(OurEnum.__dict__['_test1'], 'MyEnum')
+        self.assertFalse(WhereEnum.__dict__.get('_test1', False))
+        self.assertEqual(WhereEnum.__dict__['_test2'], 'OurEnum')
+        self.assertFalse(NeverEnum.__dict__.get('_test1', False))
+        self.assertFalse(NeverEnum.__dict__.get('_test2', False))
+
 
 class TestOrder(unittest.TestCase):
 
@@ -2573,6 +2610,42 @@ class TestFlag(unittest.TestCase):
                 'at least one thread failed while creating composite members')
         self.assertEqual(256, len(seen), 'too many composite members created')
 
+    def test_init_subclass(self):
+        class MyEnum(Flag):
+            def __init_subclass__(cls, **kwds):
+                super().__init_subclass__(**kwds)
+                self.assertFalse(cls.__dict__.get('_test', False))
+                cls._test1 = 'MyEnum'
+        #
+        class TheirEnum(MyEnum):
+            def __init_subclass__(cls, **kwds):
+                super(TheirEnum, cls).__init_subclass__(**kwds)
+                cls._test2 = 'TheirEnum'
+        class WhoseEnum(TheirEnum):
+            def __init_subclass__(cls, **kwds):
+                pass
+        class NoEnum(WhoseEnum):
+            ONE = 1
+        self.assertEqual(TheirEnum.__dict__['_test1'], 'MyEnum')
+        self.assertEqual(WhoseEnum.__dict__['_test1'], 'MyEnum')
+        self.assertEqual(WhoseEnum.__dict__['_test2'], 'TheirEnum')
+        self.assertFalse(NoEnum.__dict__.get('_test1', False))
+        self.assertFalse(NoEnum.__dict__.get('_test2', False))
+        #
+        class OurEnum(MyEnum):
+            def __init_subclass__(cls, **kwds):
+                cls._test2 = 'OurEnum'
+        class WhereEnum(OurEnum):
+            def __init_subclass__(cls, **kwds):
+                pass
+        class NeverEnum(WhereEnum):
+            ONE = 1
+        self.assertEqual(OurEnum.__dict__['_test1'], 'MyEnum')
+        self.assertFalse(WhereEnum.__dict__.get('_test1', False))
+        self.assertEqual(WhereEnum.__dict__['_test2'], 'OurEnum')
+        self.assertFalse(NeverEnum.__dict__.get('_test1', False))
+        self.assertFalse(NeverEnum.__dict__.get('_test2', False))
+
 
 class TestIntFlag(unittest.TestCase):
     """Tests of the IntFlags."""