gh-138425: Correctly partially evaluate global generics with undefined params in ref.evaluate(format=Format.FORWARDREF)

Lib/annotationlib.py

@@ -187,8 +187,11 @@ def evaluate(
             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__, **locals},
+                {**builtins.__dict__, **globals, **locals},
                 globals=globals,
                 owner=owner,
                 is_class=self.__forward_is_class__,

Lib/test/test_annotationlib.py

@@ -1675,6 +1675,24 @@ def test_name_lookup_without_eval(self):
 
         self.assertEqual(exc.exception.name, "doesntexist")
 
+    def test_evaluate_undefined_generic(self):
+        # Test the codepath where have to eval() with undefined variables.
+        generic = ForwardRef("glob[int, undef]").evaluate(format=Format.FORWARDREF, globals={"glob": dict})
+        self.assertNotIsInstance(generic, ForwardRef)
+        self.assertIs(generic.__origin__, dict)
+        self.assertIs(generic.__args__[0], int)
+
+        generic = ForwardRef("loc[int, undef]").evaluate(format=Format.FORWARDREF, locals={"loc": dict})
+        self.assertNotIsInstance(generic, ForwardRef)
+        self.assertIs(generic.__origin__, dict)
+        self.assertIs(generic.__args__[0], int)
+
+        # Ensure that globals overwrite builtins
+        generic = ForwardRef("list[int, undef]").evaluate(format=Format.FORWARDREF, globals={"list": dict})
+        self.assertNotIsInstance(generic, ForwardRef)
+        self.assertIs(generic.__origin__, dict)
+        self.assertIs(generic.__args__[0], int)
+
     def test_fwdref_invalid_syntax(self):
         fr = ForwardRef("if")
         with self.assertRaises(SyntaxError):

Misc/NEWS.d/next/Library/2025-09-03-18-26-07.gh-issue-138425.cVE9Ho.rst

@@ -0,0 +1,2 @@
+Partially evaluate undefined global generics in
+:py:meth:`annotationlib.ForwardRef.evaluate`