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gh-156413: Let a None-valued non-callable member keep the Protocol fast path #156451

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gh-156413: Let a None-valued non-callable member keep the Protocol fast path #156451

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gh-156413: Let a None-valued non-callable member keep the Protocol fa…
adamtheturtle Aug 27, 2026
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Cover a property member in the regression test
adamtheturtle Aug 27, 2026
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Cover a property member in the regression test 
A property is not callable when looked up on the class, so it lands in
__non_callable_proto_members__ alongside a plain class attribute. Both
subtests fail without the change.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016TM2nkuPFj6FFmZyUJZYUQ
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@adamtheturtle @claude
adamtheturtle and claude committed Aug 27, 2026
commit 7f7bc3fd95b33aeb00da13ab71e58ac2ea66363b
30 changes: 20 additions & 10 deletions Lib/test/test_typing.py
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Expand Up @@ -3894,22 +3894,32 @@ def test_none_on_non_callable_doesnt_defeat_the_abc_cache(self):
# class out of ABCMeta's cache and made every isinstance() call walk
# all of the protocol members again.
@runtime_checkable
class P(Protocol):
class PAttr(Protocol):
x = 1

@picnixz picnixz Aug 27, 2026

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Can you check with a protocol defining a property as well? it's not really a callable strictly speaking.

@adamtheturtle adamtheturtle Aug 27, 2026

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(Deleted comment that the bot wrote).

Yes - added in a new commit.


@runtime_checkable
class PProperty(Protocol):
@property
def x(self) -> int: ...

class B:
x = None

self.assertIsInstance(B(), P)

# The first check must have cached B as a subclass of P, so the second
# one may not touch the members at all.
typing._lazy_load_getattr_static.cache_clear()
try:
with patch.object(inspect, "getattr_static", side_effect=AssertionError):
for P in (PAttr, PProperty):
with self.subTest(protocol=P.__name__):
self.assertIn("x", P.__non_callable_proto_members__)
self.assertIsInstance(B(), P)
finally:
typing._lazy_load_getattr_static.cache_clear()

# The first check must have cached B as a subclass of P, so
# the second one may not touch the members at all.
typing._lazy_load_getattr_static.cache_clear()
try:
with patch.object(
inspect, "getattr_static", side_effect=AssertionError
):
self.assertIsInstance(B(), P)
finally:
typing._lazy_load_getattr_static.cache_clear()

def test_none_on_callable_blocks_implementation(self):
@runtime_checkable
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