Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
raminfp wants to merge 2 commits into
base: main
Choose a base branch
from
+25 −3
Open

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

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
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
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
18 changes: 18 additions & 0 deletions Lib/test/test_typing.py
View file
Open in desktop
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)]
Expand Down
6 changes: 3 additions & 3 deletions Lib/typing.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1972,6 +1972,7 @@ def _lazy_load_getattr_static():

_cleanups.append(_lazy_load_getattr_static.cache_clear)


Copy link
Copy Markdown
Member

@picnixz picnixz Mar 29, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please revert this change. Diffs should not change unrelated parts of the code as they are then less readable.

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)
Comment on lines +2488 to +2489
Copy link
Copy Markdown
Member

@picnixz picnixz Mar 29, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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.

globalns = getattr(nsobj, '__globals__', {})
if localns is None:
localns = globalns
Expand Down
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-03-28-11-43-25.gh-issue-146553.mXaWza.rst
View file
Open in desktop
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`.
Loading