mirror of https://github.com/python/cpython
gh-103479: [Enum] require __new__ to be considered a data type (GH-103495)
a mixin must either have a __new__ method, or be a dataclass, to be interpreted as a data-type
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@ -865,17 +865,19 @@ Some rules:
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4. When another data type is mixed in, the :attr:`value` attribute is *not the
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same* as the enum member itself, although it is equivalent and will compare
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equal.
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5. %-style formatting: ``%s`` and ``%r`` call the :class:`Enum` class's
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5. A ``data type`` is a mixin that defines :meth:`__new__`, or a
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:class:`~dataclasses.dataclass`
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6. %-style formatting: ``%s`` and ``%r`` call the :class:`Enum` class's
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:meth:`__str__` and :meth:`__repr__` respectively; other codes (such as
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``%i`` or ``%h`` for IntEnum) treat the enum member as its mixed-in type.
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6. :ref:`Formatted string literals <f-strings>`, :meth:`str.format`,
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7. :ref:`Formatted string literals <f-strings>`, :meth:`str.format`,
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and :func:`format` will use the enum's :meth:`__str__` method.
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.. note::
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Because :class:`IntEnum`, :class:`IntFlag`, and :class:`StrEnum` are
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designed to be drop-in replacements for existing constants, their
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:meth:`__str__` method has been reset to their data types
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:meth:`__str__` method has been reset to their data types'
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:meth:`__str__` method.
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When to use :meth:`__new__` vs. :meth:`__init__`
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@ -967,6 +967,7 @@ class EnumType(type):
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@classmethod
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def _find_data_type_(mcls, class_name, bases):
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# a datatype has a __new__ method, or a __dataclass_fields__ attribute
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data_types = set()
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base_chain = set()
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for chain in bases:
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@ -979,7 +980,7 @@ class EnumType(type):
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if base._member_type_ is not object:
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data_types.add(base._member_type_)
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break
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elif '__new__' in base.__dict__ or '__init__' in base.__dict__:
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elif '__new__' in base.__dict__ or '__dataclass_fields__' in base.__dict__:
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data_types.add(candidate or base)
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break
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else:
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@ -2737,10 +2737,10 @@ class TestSpecial(unittest.TestCase):
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return 'ha hah!'
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class Entries(Foo, Enum):
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ENTRY1 = 1
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self.assertEqual(repr(Entries.ENTRY1), '<Entries.ENTRY1: ha hah!>')
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self.assertTrue(Entries.ENTRY1.value == Foo(1), Entries.ENTRY1.value)
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self.assertTrue(isinstance(Entries.ENTRY1, Foo))
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self.assertTrue(Entries._member_type_ is Foo, Entries._member_type_)
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self.assertTrue(Entries.ENTRY1.value == Foo(1), Entries.ENTRY1.value)
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self.assertEqual(repr(Entries.ENTRY1), '<Entries.ENTRY1: ha hah!>')
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#
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# check auto-generated dataclass __repr__ is not used
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#
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@ -2787,8 +2787,7 @@ class TestSpecial(unittest.TestCase):
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DOG = ('medium', 4)
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self.assertRegex(repr(Creature.DOG), "<Creature.DOG: .*CreatureDataMixin object at .*>")
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def test_repr_with_init_data_type_mixin(self):
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# non-data_type is a mixin that doesn't define __new__
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def test_repr_with_init_mixin(self):
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class Foo:
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def __init__(self, a):
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self.a = a
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@ -2797,9 +2796,9 @@ class TestSpecial(unittest.TestCase):
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class Entries(Foo, Enum):
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ENTRY1 = 1
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#
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self.assertEqual(repr(Entries.ENTRY1), '<Entries.ENTRY1: Foo(a=1)>')
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self.assertEqual(repr(Entries.ENTRY1), 'Foo(a=1)')
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def test_repr_and_str_with_non_data_type_mixin(self):
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def test_repr_and_str_with_no_init_mixin(self):
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# non-data_type is a mixin that doesn't define __new__
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class Foo:
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def __repr__(self):
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@ -2911,6 +2910,8 @@ class TestSpecial(unittest.TestCase):
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def test_init_exception(self):
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class Base:
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def __new__(cls, *args):
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return object.__new__(cls)
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def __init__(self, x):
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raise ValueError("I don't like", x)
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with self.assertRaises(TypeError):
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