use forwardref instead

Author: mschoettle

Lib/unittest/mock.py

@@ -120,7 +120,7 @@ def _get_signature_object(func, as_instance, eat_self):
     else:
         sig_func = func
     try:
-        return func, inspect.signature(sig_func, annotation_format=Format.STRING)
+        return func, inspect.signature(sig_func, annotation_format=Format.FORWARDREF)
     except ValueError:
         # Certain callable types are not supported by inspect.signature()
         return None

Misc/NEWS.d/next/Library/2026-03-10-14-57-15.gh-issue-145754.YBL5Ko.rst

@@ -1 +1,3 @@
-Request signature during mock autospec with string annotation format
+Request signature during mock autospec with forwardref annotation format.
+This prevents runtime errors when a type referred in a type hint is
+imported within a `TYPE_CHECKING` block.