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gh-150641: Fix evaluating forward references in STRING format can 'leak' internal names in typing #150648

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Merged
JelleZijlstra merged 4 commits into from
Jul 3, 2026
Merged

gh-150641: Fix evaluating forward references in STRING format can 'leak' internal names in typing #150648

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15149f9
Fix evaluating forward references in STRING format can 'leak' interna…
ByteFlowing1337 May 31, 2026
dd079fa
Fix recursive_guard to use __forward_arg__ instead of __resolved_str__
ByteFlowing1337 May 31, 2026
6169b44
Address review
ByteFlowing1337 Jun 30, 2026
589de33
Update Misc/NEWS.d/next/Library/2026-05-31-14-39-25.gh-issue-150641.L…
ByteFlowing1337 Jun 30, 2026
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12 changes: 12 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7561,6 +7561,18 @@ def test_with_module(self):
typing.evaluate_forward_ref(
fwdref_module.fw,)

def test_evaluate_forward_ref_string_format(self):
# Test evaluating forward references in STRING format
# does not 'leak' internal names
# See https://github.com/python/cpython/issues/150641

def f(arg: unknown | str | int | list[str] | tuple[int, ...]): ...

ref = annotationlib.get_annotations(f, format=annotationlib.Format.FORWARDREF)['arg']
self.assertEqual(
typing.evaluate_forward_ref(ref, format=annotationlib.Format.STRING),
"unknown | str | int | list[str] | tuple[int, ...]",
)

class CollectionsAbcTests(BaseTestCase):

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2 changes: 1 addition & 1 deletion Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1019,7 +1019,7 @@ def evaluate_forward_ref(

"""
if format == annotationlib.Format.STRING:
return forward_ref.__forward_arg__
return forward_ref.__resolved_str__
if forward_ref.__forward_arg__ in _recursive_guard:
return forward_ref

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-05-31-14-39-25.gh-issue-150641.LLIhd1.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix bug where :func:`typing.evaluate_forward_ref` with the ``STRING`` format
could leak internal names used by the annotation machinery.
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