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bpo-44524: Don't modify MRO when inheriting from typing.Annotated (GH-27841)

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Ken Jin 2021-08-26 02:13:59 +08:00 • committed by GitHub
parent 551da597a0
commit 23384a1749
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2 changed files with 11 additions and 1 deletions
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5
Lib/test/test_typing.py
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@ -4568,6 +4568,11 @@ class AnnotatedTests(BaseTestCase):
X = List[Annotated[T, 5]] X = List[Annotated[T, 5]]
self.assertEqual(X[int], List[Annotated[int, 5]]) self.assertEqual(X[int], List[Annotated[int, 5]])
def test_annotated_mro(self):
class X(Annotated[int, (1, 10)]): ...
self.assertEqual(X.__mro__, (X, int, object),
"Annotated should be transparent.")
class TypeAliasTests(BaseTestCase): class TypeAliasTests(BaseTestCase):
def test_canonical_usage_with_variable_annotation(self): def test_canonical_usage_with_variable_annotation(self):

7
Lib/typing.py
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@ -1575,7 +1575,7 @@ class _AnnotatedAlias(_GenericAlias, _root=True):
if isinstance(origin, _AnnotatedAlias): if isinstance(origin, _AnnotatedAlias):
metadata = origin.__metadata__ + metadata metadata = origin.__metadata__ + metadata
origin = origin.__origin__ origin = origin.__origin__
super().__init__(origin, origin, name="Annotated") super().__init__(origin, origin)
self.__metadata__ = metadata self.__metadata__ = metadata
def copy_with(self, params): def copy_with(self, params):
@ -1603,6 +1603,11 @@ class _AnnotatedAlias(_GenericAlias, _root=True):
def __hash__(self): def __hash__(self):
return hash((self.__origin__, self.__metadata__)) return hash((self.__origin__, self.__metadata__))
def __getattr__(self, attr):
if attr in {'__name__', '__qualname__'}:
return 'Annotated'
return super().__getattr__(attr)
class Annotated: class Annotated:
"""Add context specific metadata to a type. """Add context specific metadata to a type.