8000 bpo-46242: better error message for extending `Enum` with members by sobolevn · Pull Request #30357 · python/cpython · GitHub
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bpo-46242: better error message for extending Enum with members #30357

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Merged
merged 3 commits into from
Jan 14, 2022
Merged

bpo-46242: better error message for extending Enum with members #30357

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958ba17
bpo-46242: better error message for extending `Enum` with members
sobolevn Jan 3, 2022
19772ac
Update 2022-01-03-16-25-06.bpo-46242.f4l_CL.rst
sobolevn Jan 3, 2022
9e7d02c
Try to use `cls._check_for_existing_members`
sobolevn Jan 3, 2022
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9 changes: 4 additions & 5 deletions Lib/enum.py
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Original file line number Diff line number Diff line change
Expand Up @@ -767,7 +767,7 @@ def _create_(cls, class_name, names, *, module=None, qualname=None, type=None, s
"""
metacls = cls.__class__
bases = (cls, ) if type is None else (type, cls)
_, first_enum = cls._get_mixins_(cls, bases)
_, first_enum = cls._get_mixins_(class_name, bases)
classdict = metacls.__prepare__(class_name, bases)

# special processing needed for names?
Expand Down Expand Up @@ -852,8 +852,8 @@ def _check_for_existing_members(class_name, bases):
% (class_name, base.__name__)
)

@staticmethod
def _get_mixins_(class_name, bases):
@classmethod
def _get_mixins_(cls, class_name, bases):
"""
Returns the type for creating enum members, and the first inherited
enum class.
Expand Down Expand Up @@ -894,9 +894,8 @@ def _find_data_type(bases):
if not issubclass(first_enum, Enum):
raise TypeError("new enumerations should be created as "
"`EnumName([mixin_type, ...] [data_type,] enum_type)`")
cls._check_for_existing_members(class_name, bases)
member_type = _find_data_type(bases) or object
if first_enum._member_names_:
raise TypeError("Cannot extend enumerations")
return member_type, first_enum

@staticmethod
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2 changes: 2 additions & 0 deletions Lib/test/test_enum.py
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8017
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Expand Up @@ -1423,6 +1423,8 @@ class MoreColor(Color):
with self.assertRaisesRegex(TypeError, "EvenMoreColor: cannot extend enumeration 'Color'"):
class EvenMoreColor(Color, IntEnum):
chartruese = 7
with self.assertRaisesRegex(TypeError, "Foo: cannot extend enumeration 'Color'"):
Color('Foo', ('pink', 'black'))

def test_exclude_methods(self):
class whatever(Enum):
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-01-03-16-25-06.bpo-46242.f4l_CL.rst
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@@ -0,0 +1 @@
Improve error message when creating a new :class:`enum.Enum` type subclassing an existing ``Enum`` with ``_member_names_`` using :meth:`enum.Enum.__call__`.
0