gh-159344: Notify ThreadingMock waiters before running side effects

Lib/test/test_unittest/testmock/testthreadingmock.py

@@ -70,6 +70,22 @@ def test_instance_check(self):
             self.assertIsInstance(something.method_1, ThreadingMock)
             self.assertIsInstance(something.method_1().method_2(), ThreadingMock)
 
+    def test_wait_after_raising_side_effect(self):
+        mock = self._make_mock(side_effect=ValueError, timeout=0)
+        with self.assertRaises(ValueError):
+            mock(1, key=2)
+        mock.wait_until_called()
+        mock.wait_until_any_call_with(1, key=2)
+
+    def test_wait_during_side_effect(self):
+        def side_effect(*args, **kwargs):
+            mock.wait_until_called()
+            mock.wait_until_any_call_with(*args, **kwargs)
+            return 42
+
+        mock = self._make_mock(side_effect=side_effect, timeout=0)
+        self.assertEqual(mock(1, key=2), 42)
+
     def test_dynamic_child_mocks_are_threading_mocks(self):
         waitable_mock = self._make_mock()
         self.assertIsInstance(waitable_mock.child, ThreadingMock)

Lib/unittest/mock.py

@@ -3107,14 +3107,12 @@ def __get_event(self, expected_args, expected_kwargs):
         return new_event
 
     def _mock_call(self, *args, **kwargs):
-        ret_value = super()._mock_call(*args, **kwargs)
-
         call_event = self.__get_event(args, kwargs)
         call_event.set()
 
         self._mock_event.set()
 
-        return ret_value
+        return super()._mock_call(*args, **kwargs)
 
     def _increment_mock_call(self, /, *args, **kwargs):
         with self._mock_calls_events_lock:

Misc/NEWS.d/next/Library/2026-10-13-20-30-00.gh-issue-159344.mOcKwa.rst

@@ -0,0 +1,2 @@
+Fix :class:`unittest.mock.ThreadingMock` to notify waiting threads when a
+call is recorded, including when its side effect raises an exception or blocks.