annotationlib: ref.evaluate(format=Format.FORWARDREF) returns a ForwardRef with a copied __globals__ that no longer updates #137969
Description
Bug report
Bug description:
This can happen internally in get_annotations and means subsequent attempts to evaluate it will fail even if the names have since been defined.
Underlying logic:
from annotationlib import get_annotations, Format
class Demo:
x: Sequence[undefined]
annos = get_annotations(Demo, format=Format.FORWARDREF)
x_anno = annos['x']
# Try to evaluate the reference, but just give a forwardref if it fails
x_repeat_anno = x_anno.evaluate(format=Format.FORWARDREF)
# The resulting reference no longer shares the globals namespace with the annotate function
print(f"{x_anno.__globals__ is Demo.__annotate__.__globals__ = }") # True
print(f"{x_repeat_anno.__globals__ is Demo.__annotate__.__globals__ = }") # False
# Define the previously undefined attributes
from collections.abc import Sequence
undefined = str
# This means evaluation fails in the second case
print(f"{x_anno.evaluate() = }") # collections.abc.Sequence[str]
print(f"{x_repeat_anno.evaluate() = }") # NameErrorThis evaluate call happens internally if get_annotations has to rely on the fallback behaviour for an unexpected exception, such as an AttributeError:
from annotationlib import get_annotations, Format
import typing
class Works:
a: Sequence[undefined]
b: unknowable
# Intentionally set up an annotation that will raise AttributeError on evaluation
class Fails:
a: Sequence[undefined]
b: typing.doesnotexist
a_works = get_annotations(Works, format=Format.FORWARDREF)['a']
a_fails = get_annotations(Fails, format=Format.FORWARDREF)['a']
# Realise the references
from collections.abc import Sequence
undefined = str
print(f"{a_works.evaluate() = }") # collections.abc.Sequence[str]
print(f"{a_fails.evaluate() = }") # NameErrorThis appears to be caused by the creation of a new globals dict here:
Lines 164 to 167 in e39255e
Commenting this out makes these examples succeed, but obviously breaks type parameters.
CPython versions tested on:
CPython main branch, 3.14
Operating systems tested on:
No response
Linked PRs
- gh-137969: Fix evaluation of
ref.evaluate(format=Format.FORWARDREF)objects #138075 - [3.14] gh-137969: Fix evaluation of
ref.evaluate(format=Format.FORWARDREF)objects (GH-138075) #140929 - Revert "gh-137969: Fix evaluation of
ref.evaluate(format=Format.FORWARDREF)objects (#138075)" #140930 - [3.14] Revert "gh-137969: Fix evaluation of
ref.evaluate(format=Format.FORWARDREF)objects (GH-138075) (#140929)" #140931 - gh-137969: Fix double evaluation of
ForwardRefs which rely on globals #140974 - [3.14] gh-137969: Fix double evaluation of
ForwardRefs which rely on globals (GH-140974) #141527