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gh-146553: Fix infinite loop in typing.get_type_hints() on circular __wrapped__ #146554

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gh-146553: Fix infinite loop in typing.get_type_hints() on circular __wrapped__ #146554

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61a821b
gh-146553: Fix infinite loop in typing.get_type_hints() on circular _…
raminfp Mar 28, 2026
4e9afee
gh-146553: Use inspect.unwrap() for cycle detection instead of custom…
raminfp Mar 28, 2026
e205384
gh-146553: Use _lazy_load_unwrap() helper instead of local import in …
raminfp Mar 30, 2026
27c948d
gh-146553: Replace _lazy_load_* helpers with _LazyInspect for lazy in…
raminfp Mar 30, 2026
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18 changes: 18 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6837,6 +6837,24 @@ def test_get_type_hints_wrapped_decoratored_func(self):
self.assertEqual(gth(ForRefExample.func), expects)
self.assertEqual(gth(ForRefExample.nested), expects)

def test_get_type_hints_wrapped_cycle_self(self):
# gh-146553: __wrapped__ self-reference must raise ValueError,
# not loop forever.
def f(x: int) -> str: ...
f.__wrapped__ = f
with self.assertRaisesRegex(ValueError, 'wrapper loop'):
get_type_hints(f)

def test_get_type_hints_wrapped_cycle_mutual(self):
# gh-146553: mutual __wrapped__ cycle (a -> b -> a) must raise
# ValueError, not loop forever.
def a(): ...
def b(): ...
a.__wrapped__ = b
b.__wrapped__ = a
with self.assertRaisesRegex(ValueError, 'wrapper loop'):
get_type_hints(a)

def test_get_type_hints_annotated(self):
def foobar(x: List['X']): ...
X = Annotated[int, (1, 10)]
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6 changes: 3 additions & 3 deletions Lib/typing.py
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Expand Up @@ -1972,6 +1972,7 @@ def _lazy_load_getattr_static():

_cleanups.append(_lazy_load_getattr_static.cache_clear)


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def _pickle_psargs(psargs):
return ParamSpecArgs, (psargs.__origin__,)

Expand Down Expand Up @@ -2483,10 +2484,9 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
if isinstance(obj, types.ModuleType):
globalns = obj.__dict__
else:
nsobj = obj
# Find globalns for the unwrapped object.
while hasattr(nsobj, '__wrapped__'):
nsobj = nsobj.__wrapped__
import inspect
nsobj = inspect.unwrap(obj)
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@picnixz picnixz Mar 29, 2026

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Everytime I see local imports for inspect, I feel that we need to have a lower-level inspect utililty that can have less functions but more common to avoid having to import inspect.

What I can suggest for this specific PR is to use lazy import inspect instead at the top-level to make it a bit cleaner. For backports, we'll however need to use a local import. Note that we have other places with a local import to inspect, which you can eventually remove since we would have both a lazy and a local import (which would be redundant). I'll let @JelleZijlstra decide whether to want lazy imports.

If we switch to lazy imports, we'll also need to update the lazy import tests somewhere to check that inspect is lazily imported.

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@JelleZijlstra JelleZijlstra Mar 30, 2026

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Maybe inspect.unwrap should live in functools instead, it's closely related to functools.wraps after all. But it's probably too late for that. Lazy importing sounds good to me.

globalns = getattr(nsobj, '__globals__', {})
if localns is None:
localns = globalns
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-03-28-11-43-25.gh-issue-146553.mXaWza.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
Fix :func:`typing.get_type_hints` hanging indefinitely when a callable has a
circular ``__wrapped__`` chain (e.g. ``f.__wrapped__ = f``). A
:exc:`ValueError` is now raised on cycle detection, matching the behavior of
:func:`inspect.unwrap`.
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