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gh-155852: Do not cancel remaining Executor.map calls on a callable's TimeoutError #155853

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gh-155852: Do not cancel remaining Executor.map calls on a callable's TimeoutError #155853

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gh-155852: Do not cancel remaining Executor.map calls on a callable's…
tonghuaroot Aug 15, 2026
355dc7c
Trim the regression test comment
tonghuaroot Aug 15, 2026
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6 changes: 5 additions & 1 deletion Lib/concurrent/futures/_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -310,7 +310,11 @@ def _result_or_cancel(fut, timeout=None):
try:
try:
return (fut.result(timeout), None)
except TimeoutError:
except TimeoutError as exc:
if fut.done():
# The future already finished, so this is the callable's own
# TimeoutError, not the map() timeout waiting for the future.
return (None, exc)
raise
except BaseException as exc:
return (None, exc)
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17 changes: 17 additions & 0 deletions Lib/test/test_concurrent_futures/executor.py
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Expand Up @@ -29,6 +29,13 @@ def raiser(exception, msg='std'):
raise exception(msg)


# Used in test_map_timeout_from_callable
def timeout_on_one(x):
if x == 1:
raise TimeoutError
return x


class FalseyBoolException(Exception):
def __bool__(self):
return False
Expand Down Expand Up @@ -87,6 +94,16 @@ def test_map_exception(self):
self.assertRaises(StopIteration, next, i)
self.assertRaises(StopIteration, next, i)

@warnings_helper.ignore_fork_in_thread_deprecation_warnings()
def test_map_timeout_from_callable(self):
# A TimeoutError from the callable is not the map() timeout.
i = self.executor.map(timeout_on_one, [0, 1, 2, 3])
self.assertEqual(next(i), 0)
self.assertRaises(TimeoutError, next, i)
self.assertEqual(next(i), 2)
self.assertEqual(next(i), 3)
self.assertRaises(StopIteration, next, i)

@warnings_helper.ignore_fork_in_thread_deprecation_warnings()
@support.requires_resource('walltime')
def test_map_timeout(self):
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-08-15-16-00-00.gh-issue-155852.MapTmo.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix :meth:`concurrent.futures.Executor.map` cancelling the remaining calls when
the mapped callable raises :exc:`TimeoutError`; such an exception is now
propagated like any other, without stopping the iteration.
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