bpo-41517: do not allow Enums to be extended (#22271)
fix bug that let Enums be extended via multiple inheritance
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parent
0705ec8a14
commit
3064dbf5df
19
Lib/enum.py
19
Lib/enum.py
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@ -124,10 +124,12 @@ class EnumMeta(type):
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"""Metaclass for Enum"""
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@classmethod
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def __prepare__(metacls, cls, bases):
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# check that previous enum members do not exist
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metacls._check_for_existing_members(cls, bases)
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# create the namespace dict
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enum_dict = _EnumDict()
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# inherit previous flags and _generate_next_value_ function
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member_type, first_enum = metacls._get_mixins_(bases)
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member_type, first_enum = metacls._get_mixins_(cls, bases)
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if first_enum is not None:
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enum_dict['_generate_next_value_'] = getattr(first_enum, '_generate_next_value_', None)
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return enum_dict
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@ -143,7 +145,7 @@ class EnumMeta(type):
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ignore = classdict['_ignore_']
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for key in ignore:
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classdict.pop(key, None)
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member_type, first_enum = metacls._get_mixins_(bases)
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member_type, first_enum = metacls._get_mixins_(cls, bases)
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__new__, save_new, use_args = metacls._find_new_(classdict, member_type,
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first_enum)
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@ -402,7 +404,7 @@ class EnumMeta(type):
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"""
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metacls = cls.__class__
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bases = (cls, ) if type is None else (type, cls)
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_, first_enum = cls._get_mixins_(bases)
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_, first_enum = cls._get_mixins_(cls, bases)
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classdict = metacls.__prepare__(class_name, bases)
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# special processing needed for names?
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@ -475,7 +477,14 @@ class EnumMeta(type):
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return cls
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@staticmethod
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def _get_mixins_(bases):
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def _check_for_existing_members(class_name, bases):
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for chain in bases:
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for base in chain.__mro__:
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if issubclass(base, Enum) and base._member_names_:
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raise TypeError("%s: cannot extend enumeration %r" % (class_name, base.__name__))
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@staticmethod
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def _get_mixins_(class_name, bases):
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"""Returns the type for creating enum members, and the first inherited
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enum class.
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@ -500,7 +509,7 @@ class EnumMeta(type):
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elif not issubclass(base, Enum):
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candidate = base
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if len(data_types) > 1:
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raise TypeError('too many data types: %r' % data_types)
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raise TypeError('%r: too many data types: %r' % (class_name, data_types))
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elif data_types:
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return data_types[0]
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else:
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@ -1009,6 +1009,9 @@ class TestEnum(unittest.TestCase):
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cyan = 4
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magenta = 5
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yellow = 6
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with self.assertRaisesRegex(TypeError, "EvenMoreColor: cannot extend enumeration 'Color'"):
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class EvenMoreColor(Color, IntEnum):
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chartruese = 7
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def test_exclude_methods(self):
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class whatever(Enum):
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@ -0,0 +1 @@
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fix bug allowing Enums to be extended via multiple inheritance
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