gh-92118: Add test for traceback when exception is modified by (Async)ExitStack.__exit__ (GH-92339)

Lib/test/test_contextlib.py

@@ -748,6 +748,38 @@ class TestBaseExitStack:
             stack.push(lambda *exc: True)
             1/0
 
+    def test_exit_exception_traceback(self):
+        # This test captures the current behavior of ExitStack so that we know
+        # if we ever unintendedly change it. It is not a statement of what the
+        # desired behavior is (for instance, we may want to remove some of the
+        # internal contextlib frames).
+
+        def raise_exc(exc):
+            raise exc
+
+        try:
+            with self.exit_stack() as stack:
+                stack.callback(raise_exc, ValueError)
+                1/0
+        except ValueError as e:
+            exc = e
+
+        self.assertIsInstance(exc, ValueError)
+        ve_frames = traceback.extract_tb(exc.__traceback__)
+        expected = \
+            [('test_exit_exception_traceback', 'with self.exit_stack() as stack:')] + \
+            self.callback_error_internal_frames + \
+            [('_exit_wrapper', 'callback(*args, **kwds)'),
+             ('raise_exc', 'raise exc')]
+
+        self.assertEqual(
+            [(f.name, f.line) for f in ve_frames], expected)
+
+        self.assertIsInstance(exc.__context__, ZeroDivisionError)
+        zde_frames = traceback.extract_tb(exc.__context__.__traceback__)
+        self.assertEqual([(f.name, f.line) for f in zde_frames],
+                         [('test_exit_exception_traceback', '1/0')])
+
     def test_exit_exception_chaining_reference(self):
         # Sanity check to make sure that ExitStack chaining matches
         # actual nested with statements
@@ -1017,6 +1049,10 @@ class TestBaseExitStack:
 
 class TestExitStack(TestBaseExitStack, unittest.TestCase):
     exit_stack = ExitStack
+    callback_error_internal_frames = [
+        ('__exit__', 'raise exc_details[1]'),
+        ('__exit__', 'if cb(*exc_details):'),
+    ]
 
 
 class TestRedirectStream:

Lib/test/test_contextlib_async.py

@@ -487,6 +487,13 @@ class TestAsyncExitStack(TestBaseExitStack, unittest.TestCase):
             return self.run_coroutine(self.__aexit__(*exc_details))
 
     exit_stack = SyncAsyncExitStack
+    callback_error_internal_frames = [
+        ('__exit__', 'return self.run_coroutine(self.__aexit__(*exc_details))'),
+        ('run_coroutine', 'raise exc'),
+        ('run_coroutine', 'raise exc'),
+        ('__aexit__', 'raise exc_details[1]'),
+        ('__aexit__', 'cb_suppress = cb(*exc_details)'),
+    ]
 
     def setUp(self):
         self.loop = asyncio.new_event_loop()