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gh-137969: Fix double evaluation of ForwardRefs which rely on globals #140974

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Merged
JelleZijlstra merged 11 commits into from
Nov 13, 2025
+72 −15
Merged

gh-137969: Fix double evaluation of ForwardRefs which rely on globals #140974

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8708272
Extract type param scope instead of copying globals dict
dr-carlos Nov 3, 2025
fc00d21
Add test for re-evaluating ForwardRef generics
dr-carlos Nov 4, 2025
71c9074
Simplify scope logic in `ref.evaluate()` to ensure double-evaluation …
dr-carlos Nov 4, 2025
1c79ac7
Add NEWS entry
dr-carlos Nov 4, 2025
2630802
Update `del` to end of test_re_evaluate_generics
dr-carlos Nov 4, 2025
d02e635
Create new locals dict when necessary
dr-carlos Nov 4, 2025
02b8a83
Revert "Update `del` to end of test_re_evaluate_generics"
dr-carlos Nov 6, 2025
e20da27
Use locals.setdefault() instead of manually checking if key in dict
dr-carlos Nov 6, 2025
65c40d3
Add test to check if arguments to `ref.evaluate()` are mutated
dr-carlos Nov 6, 2025
41c3e64
Include less code within `cell.cell_contents` try-except block
dr-carlos Nov 13, 2025
f457725
Merge branch 'main' into fwdref-double-eval
JelleZijlstra Nov 13, 2025
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Extract type param scope instead of copying globals dict
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@dr-carlos
dr-carlos committed Nov 4, 2025
commit 8708272e86ba62767a5eb23b171633a205728b24
19 changes: 12 additions & 7 deletions Lib/annotationlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -161,14 +161,17 @@ def evaluate(
# as a way of emulating annotation scopes when calling `eval()`
type_params = getattr(owner, "__type_params__", None)

# Type parameters exist in their own scope, which is logically
# between the locals and the globals. We simulate this by adding
# them to the globals. Similar reasoning applies to nonlocals stored in cells.
if type_params is not None or isinstance(self.__cell__, dict):
# Nonlocals logically sit between the locals and the globals. We simulate this
# by overriding the globals.
if isinstance(self.__cell__, dict):
globals = dict(globals)

# Type parameters exist in their own scope, which is logically
# between the locals and the globals.
type_param_scope = {}
if type_params is not None:
for param in type_params:
globals[param.__name__] = param
type_param_scope[param.__name__] = param
if isinstance(self.__cell__, dict):
for cell_name, cell_value in self.__cell__.items():
try:
Expand All @@ -182,6 +185,8 @@ def evaluate(
if arg.isidentifier() and not keyword.iskeyword(arg):
if arg in locals:
return locals[arg]
elif arg in type_param_scope:
return type_param_scope[arg]
elif arg in globals:
return globals[arg]
elif hasattr(builtins, arg):
Expand All @@ -193,15 +198,15 @@ def evaluate(
else:
code = self.__forward_code__
try:
return eval(code, globals=globals, locals=locals)
return eval(code, globals=globals, locals={**type_param_scope, **locals})
except Exception:
if not is_forwardref_format:
raise

# All variables, in scoping order, should be checked before
# triggering __missing__ to create a _Stringifier.
new_locals = _StringifierDict(
{**builtins.__dict__, **globals, **locals},
{**builtins.__dict__, **globals, **type_param_scope, **locals},
globals=globals,
owner=owner,
is_class=self.__forward_is_class__,
Expand Down