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

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Merged
merged 5 commits into from
Aug 25, 2021
Merged

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

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ce19238
exclude Annotated from _name temporarily
Fidget-Spinner Aug 19, 2021
a943fce
stricter tests
Fidget-Spinner Aug 19, 2021
f26b866
Merge remote-tracking branch 'upstream/main' into name_annotated
Fidget-Spinner Aug 21, 2021
1cebc04
fix tests, remove news
Fidget-Spinner Aug 21, 2021
ba279d2
__name__ for Annotated is 'Annotated'
Fidget-Spinner Aug 21, 2021
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5 changes: 5 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4568,6 +4568,11 @@ def test_annotated_in_other_types(self):
X = List[Annotated[T, 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):
def test_canonical_usage_with_variable_annotation(self):
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7 changes: 6 additions & 1 deletion Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1575,7 +1575,7 @@ def __init__(self, origin, metadata):
if isinstance(origin, _AnnotatedAlias):
metadata = origin.__metadata__ + metadata
origin = origin.__origin__
super().__init__(origin, origin, name="Annotated")
super().__init__(origin, origin)
self.__metadata__ = metadata

def copy_with(self, params):
Expand Down Expand Up @@ -1603,6 +1603,11 @@ def __eq__(self, other):
def __hash__(self):
return hash((self.__origin__, self.__metadata__))

def __getattr__(self, attr):
if attr in {'__name__', '__qualname__'}:
return 'Annotated'
return super().__getattr__(attr)


class Annotated:
"""Add context specific metadata to a type.
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