[Python-checkins] bpo-42851: [Enum] remove brittle __init_subclass__ support (GH-24154)
ethanfurman
webhook-mailer at python.org
Thu Jan 7 16:18:16 EST 2021
https://github.com/python/cpython/commit/a581a868d97f649aedf868a1d27865a10925c73a
commit: a581a868d97f649aedf868a1d27865a10925c73a
branch: master
author: Ethan Furman <ethan at stoneleaf.us>
committer: ethanfurman <ethan at stoneleaf.us>
date: 2021-01-07T13:17:55-08:00
summary:
bpo-42851: [Enum] remove brittle __init_subclass__ support (GH-24154)
Solution to support calls to `__init_subclass__` with members defined is too brittle and breaks with certain mixins.
files:
A Misc/NEWS.d/next/Library/2021-01-07-11-44-22.bpo-42851.uyQFyd.rst
M Lib/enum.py
M Lib/test/test_enum.py
diff --git a/Lib/enum.py b/Lib/enum.py
index 75249bfdc1be1..a93642068f743 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -9,14 +9,6 @@
]
-class _NoInitSubclass:
- """
- temporary base class to suppress calling __init_subclass__
- """
- @classmethod
- def __init_subclass__(cls, **kwds):
- pass
-
def _is_descriptor(obj):
"""
Returns True if obj is a descriptor, False otherwise.
@@ -227,22 +219,7 @@ def __new__(metacls, cls, bases, classdict, **kwds):
if '__doc__' not in classdict:
classdict['__doc__'] = 'An enumeration.'
- # postpone calling __init_subclass__
- if '__init_subclass__' in classdict and classdict['__init_subclass__'] is None:
- raise TypeError('%s.__init_subclass__ cannot be None')
- # remove current __init_subclass__ so previous one can be found with getattr
- new_init_subclass = classdict.pop('__init_subclass__', None)
- # create our new Enum type
- if bases:
- bases = (_NoInitSubclass, ) + bases
- enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
- enum_class.__bases__ = enum_class.__bases__[1:] #or (object, )
- else:
- enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
- old_init_subclass = getattr(enum_class, '__init_subclass__', None)
- # and restore the new one (if there was one)
- if new_init_subclass is not None:
- enum_class.__init_subclass__ = classmethod(new_init_subclass)
+ enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
enum_class._member_names_ = [] # names in definition order
enum_class._member_map_ = {} # name->value map
enum_class._member_type_ = member_type
@@ -354,9 +331,6 @@ def __new__(metacls, cls, bases, classdict, **kwds):
if _order_ != enum_class._member_names_:
raise TypeError('member order does not match _order_')
- # finally, call parents' __init_subclass__
- if Enum is not None and old_init_subclass is not None:
- old_init_subclass(**kwds)
return enum_class
def __bool__(self):
@@ -734,9 +708,6 @@ def _generate_next_value_(name, start, count, last_values):
else:
return start
- def __init_subclass__(cls, **kwds):
- super().__init_subclass__(**kwds)
-
@classmethod
def _missing_(cls, value):
return None
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 19b4fa5464ce7..196438ada1582 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -2119,52 +2119,7 @@ class ThirdFailedStrEnum(StrEnum):
one = '1'
two = b'2', 'ascii', 9
- def test_init_subclass_calling(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))
- def test_init_subclass_parameter(self):
- class multiEnum(Enum):
- def __init_subclass__(cls, multi):
- for member in cls:
- member._as_parameter_ = multi * member.value
- class E(multiEnum, multi=3):
- A = 1
- B = 2
- self.assertEqual(E.A._as_parameter_, 3)
- self.assertEqual(E.B._as_parameter_, 6)
@unittest.skipUnless(
sys.version_info[:2] == (3, 9),
diff --git a/Misc/NEWS.d/next/Library/2021-01-07-11-44-22.bpo-42851.uyQFyd.rst b/Misc/NEWS.d/next/Library/2021-01-07-11-44-22.bpo-42851.uyQFyd.rst
new file mode 100644
index 0000000000000..927283521e80e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-01-07-11-44-22.bpo-42851.uyQFyd.rst
@@ -0,0 +1 @@
+remove __init_subclass__ support for Enum members
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