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gh-105237: Allow calling issubclass(X, typing.Protocol) again #105239

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Merged
JelleZijlstra merged 6 commits into from
Jun 5, 2023
+65 −0
Merged

gh-105237: Allow calling issubclass(X, typing.Protocol) again #105239

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a6b11b0
Allow calling `issubclass(X, Protocol)`
AlexWaygood Jun 2, 2023
36b2ac9
Add back some implementation details so we don't unnecessarily break …
AlexWaygood Jun 2, 2023
db51c8d
Revert unnecessary changes to tests
AlexWaygood Jun 2, 2023
776bf2b
Fix longstanding bug and add many tests
AlexWaygood Jun 2, 2023
ffb7f1c
Small micro-optimisation
AlexWaygood Jun 2, 2023
b85a320
Cleaner solution
AlexWaygood Jun 2, 2023
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Small micro-optimisation
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@AlexWaygood
AlexWaygood committed Jun 2, 2023
commit ffb7f1ccddcb0dafb9221c615e17add7ba746243
9 changes: 9 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2771,6 +2771,15 @@ def x(self): pass
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
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4 changes: 2 additions & 2 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1782,11 +1782,11 @@ 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')
if cls is Protocol:
return type.__subclasscheck__(cls, other)
if (
getattr(cls, '_is_protocol', False)
and not _allow_reckless_class_checks()
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