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gh-92118: Add test for traceback when exception is modified by ExitStack.__exit__ #92339

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Merged
merged 3 commits into from
May 5, 2022
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gh-92118: Add test for traceback when exception is modified by ExitStack.__exit__ #92339

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01ee553
gh-92118: Add test for traceback when exception is modified by ExitSt…
iritkatriel May 5, 2022
f77f1cd
remove redundant assertions
iritkatriel May 5, 2022
235044a
fix test_contextlib_async
iritkatriel May 5, 2022
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33 changes: 33 additions & 0 deletions Lib/test/test_contextlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -748,6 +748,39 @@ def test_exit_suppress(self):
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__)
self.assertEqual(len(ve_frames), 5)
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It is redundant, And if it fail, the report will be less informative than failing the test which compares lists.

self.assertEqual(
[(f.name, f.line) for f in ve_frames],
[('test_exit_exception_traceback', 'with self.exit_stack() as stack:'),
('__exit__', 'raise exc_details[1]'),
('__exit__', 'if cb(*exc_details):'),
('_exit_wrapper', 'callback(*args, **kwds)'),
('raise_exc', 'raise exc')])

self.assertIsInstance(exc.__context__, ZeroDivisionError)
zde_frames = traceback.extract_tb(exc.__context__.__traceback__)
self.assertEqual(len(zde_frames), 1)
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
Expand Down