diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py index dc1514d63b7775..bf23eb6bdcb090 100644 --- a/Lib/test/test_typing.py +++ b/Lib/test/test_typing.py @@ -1074,6 +1074,32 @@ class CG(PG[T]): pass with self.assertRaises(TypeError): CG[int](42) + def test_protocol_defining_init_does_not_get_overridden(self): + # check that P.__init__ doesn't get clobbered + # see https://bugs.python.org/issue44807 + + class P(Protocol): + x: int + def __init__(self, x: int) -> None: + self.x = x + class C: pass + + c = C() + P.__init__(c, 1) + self.assertEqual(c.x, 1) + + def test_concrete_class_inheriting_init_from_protocol(self): + class P(Protocol): + x: int + def __init__(self, x: int) -> None: + self.x = x + + class C(P): pass + + c = C(1) + self.assertIsInstance(c, C) + self.assertEqual(c.x, 1) + def test_cannot_instantiate_abstract(self): @runtime_checkable class P(Protocol): diff --git a/Lib/typing.py b/Lib/typing.py index ad1435ed23d272..06c2818daba1ef 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -1741,7 +1741,8 @@ def _proto_hook(other): issubclass(base, Generic) and base._is_protocol): raise TypeError('Protocols can only inherit from other' ' protocols, got %r' % base) - cls.__init__ = _no_init_or_replace_init + if cls.__init__ is Protocol.__init__: + cls.__init__ = _no_init_or_replace_init class _AnnotatedAlias(_GenericAlias, _root=True): diff --git a/Misc/NEWS.d/next/Library/2022-03-02-04-25-58.bpo-44807.gHNC9J.rst b/Misc/NEWS.d/next/Library/2022-03-02-04-25-58.bpo-44807.gHNC9J.rst new file mode 100644 index 00000000000000..4757d3420caf8a --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-03-02-04-25-58.bpo-44807.gHNC9J.rst @@ -0,0 +1 @@ +:class:`typing.Protocol` no longer silently replaces :meth:`__init__` methods defined on subclasses. Patch by Adrian Garcia Badaracco.