8000 bpo-46571: improve `typing.no_type_check` to skip foreign objects · python/cpython@a03009c · GitHub
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bpo-46571: improve typing.no_type_check to skip foreign objects
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4 files changed

+75
-7
lines changed

4 files changed

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‎Doc/library/typing.rst

Lines changed: 2 additions & 2 deletions
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@@ -1999,8 +1999,8 @@ Functions and decorators
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Decorator to indicate that annotations are not type hints.
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This works as class or function :term:`decorator`. With a class, it
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applies recursively to all methods defined in that class (but not
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to methods defined in its superclasses or subclasses).
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applies recursively to all methods and classes defined in that class
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(but not to methods defined in its superclasses or subclasses).
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This mutates the function(s) in place.
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‎Lib/test/test_typing.py

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@@ -2965,9 +2965,73 @@ def meth(self, x: int): ...
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@no_type_check
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class D(C):
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c = C
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# verify that @no_type_check never affects bases
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self.assertEqual(get_type_hints(C.meth), {'x': int})
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# and never child classes:
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class Child(D):
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def foo(self, x: int): ...
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self.assertEqual(get_type_hints(Child.foo), {'x': int})
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def test_no_type_check_nested_types(self):
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# See https://bugs.python.org/issue46571
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class Other:
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o: int
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class B: # Has the same `__name__`` as `A.B` and different `__qualname__`
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o: int
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@no_type_check
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class A:
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a: int
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class B:
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b: int
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class C:
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c: int
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class D:
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d: int
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Other = Other
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for klass in [A, A.B, A.B.C, A.D]:
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with self.subTest(klass=klass):
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self.assertTrue(klass.__no_type_check__)
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self.assertEqual(get_type_hints(klass), {})
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for not_modified in [Other, B]:
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with self.subTest(not_modified=not_modified):
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with self.assertRaises(AttributeError):
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not_modified.__no_type_check__
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self.assertNotEqual(get_type_hints(not_modified), {})
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def test_no_type_check_foreign_functions(self):
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# We should not modify this function:
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def some(*args: int) -> int:
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...
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@no_type_check
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class A:
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some_alias = some
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some_class = classmethod(some)
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some_static = staticmethod(some)
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with self.assertRaises(AttributeError):
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some.__no_type_check__
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def test_no_type_check_lambda(self):
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@no_type_check
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class A:
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# Corner case: `lambda` is both an assignment and a function:
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bar: Callable[[int], int] = lambda arg: arg
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self.assertTrue(A.bar.__no_type_check__)
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self.assertEqual(get_type_hints(A.bar), {})
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def test_no_type_check_TypeError(self):
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# This simply should not fail with
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# `TypeError: can't set attributes of built-in/extension type 'dict'`
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no_type_check(dict)
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def test_no_type_check_forward_ref_as_string(self):
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class C:
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foo: typing.ClassVar[int] = 7

‎Lib/typing.py

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1959,11 +1959,13 @@ def no_type_check(arg):
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This mutates the function(s) or class(es) in place.
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"""
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if isinstance(arg, type):
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arg_attrs = arg.__dict__.copy()
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for attr, val in arg.__dict__.items():
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if val in arg.__bases__ + (arg,):
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arg_attrs.pop(attr)
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for obj in arg_attrs.values():
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for obj in arg.__dict__.values():
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if (hasattr(obj, '__qualname__')
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and obj.__qualname__ != f'{arg.__qualname__}.{obj.__name__}'):
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# We only modify objects that are defined in this type directly.
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# If classes / methods are nested in multiple layers,
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# we will modify them when processing their direct holders.
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continue
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if isinstance(obj, types.FunctionType):
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obj.__no_type_check__ = True
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if isinstance(obj, type):

‎Misc/NEWS.d/next/Library/2022-02-01-11-21-34.bpo-46571.L40xUJ.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
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Improve :func:`typing.no_type_check` to not modify foreign functions and
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types.

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