diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py index f7114eb1fdbdd9..f6e0d203b5be86 100644 --- a/Lib/test/test_typing.py +++ b/Lib/test/test_typing.py @@ -2758,6 +2758,65 @@ def x(self): ... with self.assertRaisesRegex(TypeError, only_classes_allowed): issubclass(1, BadPG) + def test_issubclass_and_isinstance_on_Protocol_itself(self): + class C: + def x(self): pass + + self.assertNotIsSubclass(object, Protocol) + self.assertNotIsInstance(object(), Protocol) + + self.assertNotIsSubclass(str, Protocol) + self.assertNotIsInstance('foo', Protocol) + + self.assertNotIsSubclass(C, Protocol) + self.assertNotIsInstance(C(), Protocol) + + only_classes_allowed = r"issubclass\(\) arg 1 must be a class" + + with self.assertRaisesRegex(TypeError, only_classes_allowed): + issubclass(1, Protocol) + with self.assertRaisesRegex(TypeError, only_classes_allowed): + issubclass('foo', Protocol) + with self.assertRaisesRegex(TypeError, only_classes_allowed): + issubclass(C(), Protocol) + + T = TypeVar('T') + + @runtime_checkable + class EmptyProtocol(Protocol): pass + + @runtime_checkable + class SupportsStartsWith(Protocol): + def startswith(self, x: str) -> bool: ... + + @runtime_checkable + class SupportsX(Protocol[T]): + def x(self): ... + + for proto in EmptyProtocol, SupportsStartsWith, SupportsX: + with self.subTest(proto=proto.__name__): + self.assertIsSubclass(proto, Protocol) + + # gh-105237 / PR #105239: + # check that the presence of Protocol subclasses + # where `issubclass(X, )` evaluates to True + # doesn't influence the result of `issubclass(X, Protocol)` + + self.assertIsSubclass(object, EmptyProtocol) + self.assertIsInstance(object(), EmptyProtocol) + self.assertNotIsSubclass(object, Protocol) + self.assertNotIsInstance(object(), Protocol) + + self.assertIsSubclass(str, SupportsStartsWith) + self.assertIsInstance('foo', SupportsStartsWith) + self.assertNotIsSubclass(str, Protocol) + self.assertNotIsInstance('foo', Protocol) + + self.assertIsSubclass(C, SupportsX) + self.assertIsInstance(C(), SupportsX) + self.assertNotIsSubclass(C, Protocol) + self.assertNotIsInstance(C(), Protocol) + def test_protocols_issubclass_non_callable(self): class C: x = 1 diff --git a/Lib/typing.py b/Lib/typing.py index f589be7295c755..c831ba847fc384 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -1782,6 +1782,8 @@ def __init__(cls, *args, **kwargs): ) def __subclasscheck__(cls, other): + if cls is Protocol: + return type.__subclasscheck__(cls, other) if not isinstance(other, type): # Same error message as for issubclass(1, int). raise TypeError('issubclass() arg 1 must be a class') @@ -1803,6 +1805,8 @@ def __subclasscheck__(cls, other): def __instancecheck__(cls, instance): # We need this method for situations where attributes are # assigned in __init__. + if cls is Protocol: + return type.__instancecheck__(cls, instance) if not getattr(cls, "_is_protocol", False): # i.e., it's a concrete subclass of a protocol return super().__instancecheck__(instance) diff --git a/Misc/NEWS.d/next/Library/2023-06-02-14-57-11.gh-issue-105239.SAmuuj.rst b/Misc/NEWS.d/next/Library/2023-06-02-14-57-11.gh-issue-105239.SAmuuj.rst new file mode 100644 index 00000000000000..35e1b1a217b3a4 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2023-06-02-14-57-11.gh-issue-105239.SAmuuj.rst @@ -0,0 +1,2 @@ +Fix longstanding bug where ``issubclass(object, typing.Protocol)`` would +evaluate to ``True`` in some edge cases. Patch by Alex Waygood. pFad - Phonifier reborn

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