gh-141174: Test re-stringifying a `ForwardRef` (#155689)

https://github.com/python/cpython/commit/5dab4902dd24a692b9f9c0cea1cad14c429307c2
commit: 5dab4902dd24a692b9f9c0cea1cad14c429307c2
branch: main
author: dr-carlos <[email protected]>
committer: JelleZijlstra <[email protected]>
date: 2026-08-13T14:14:33Z
summary:

gh-141174: Test re-stringifying a `ForwardRef` (#155689)

Test that re-evaluating a `ForwardRef` with `STRING` format uses the cache

files:
M Lib/test/test_annotationlib.py

diff --git a/Lib/test/test_annotationlib.py b/Lib/test/test_annotationlib.py
index 5087c3ca425f1f..5bfcf5ce4131e3 100644
--- a/Lib/test/test_annotationlib.py
+++ b/Lib/test/test_annotationlib.py
@@ -2133,8 +2133,13 @@ def f(a: unknown | str | int | list[str] | tuple[int, ...]): ...
         self.assertIsNone(fr.__resolved_str_cache__)
 
         self.assertEqual(fr.evaluate(format=Format.STRING), "unknown | str | int | list[str] | tuple[int, ...]")
+
+        # Test that the cache is now set correctly
         self.assertEqual(fr.__resolved_str_cache__, "unknown | str | int | list[str] | tuple[int, ...]")
 
+        # Test that future evaluations return the same cache
+        self.assertIs(fr.evaluate(format=Format.STRING), fr.__resolved_str_cache__)
+
     def test_evaluate_forwardref_format(self):
         fr = ForwardRef("undef")
         evaluated = fr.evaluate(format=Format.FORWARDREF)

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