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Code Issues Projects Releases Packages Wiki Activity Actions 17

bpo-31033: Improve the traceback for cancelled asyncio tasks (GH-19951)

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When an asyncio.Task is cancelled, the exception traceback now
starts with where the task was first interrupted.  Previously,
the traceback only had "depth one."
This commit is contained in:
Chris Jerdonek 2020-05-17 22:47:31 -07:00 • committed by GitHub
parent d17f3d8315
commit da742ba826
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GPG key ID: 4AEE18F83AFDEB23
10 changed files with 290 additions and 80 deletions
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26
Lib/asyncio/tasks.py
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@ -270,8 +270,7 @@ class Task(futures._PyFuture): # Inherit Python Task implementation
f'_step(): already done: {self!r}, {exc!r}')
if self._must_cancel:
if not isinstance(exc, exceptions.CancelledError):
exc = exceptions.CancelledError(''
if self._cancel_message is None else self._cancel_message)
exc = self._make_cancelled_error()
self._must_cancel = False
coro = self._coro
self._fut_waiter = None
@ -293,11 +292,9 @@ class Task(futures._PyFuture): # Inherit Python Task implementation
else:
super().set_result(exc.value)
except exceptions.CancelledError as exc:
if exc.args:
cancel_msg = exc.args[0]
else:
cancel_msg = None
super().cancel(msg=cancel_msg) # I.e., Future.cancel(self).
# Save the original exception so we can chain it later.
self._cancelled_exc = exc
super().cancel() # I.e., Future.cancel(self).
except (KeyboardInterrupt, SystemExit) as exc:
super().set_exception(exc)
raise
@ -787,8 +784,7 @@ def gather(*coros_or_futures, loop=None, return_exceptions=False):
# Check if 'fut' is cancelled first, as
# 'fut.exception()' will *raise* a CancelledError
# instead of returning it.
exc = exceptions.CancelledError(''
if fut._cancel_message is None else fut._cancel_message)
exc = fut._make_cancelled_error()
outer.set_exception(exc)
return
else:
@ -804,9 +800,12 @@ def gather(*coros_or_futures, loop=None, return_exceptions=False):
for fut in children:
if fut.cancelled():
# Check if 'fut' is cancelled first, as
# 'fut.exception()' will *raise* a CancelledError
# instead of returning it.
# Check if 'fut' is cancelled first, as 'fut.exception()'
# will *raise* a CancelledError instead of returning it.
# Also, since we're adding the exception return value
# to 'results' instead of raising it, don't bother
# setting __context__. This also lets us preserve
# calling '_make_cancelled_error()' at most once.
res = exceptions.CancelledError(
'' if fut._cancel_message is None else
fut._cancel_message)
@ -820,8 +819,7 @@ def gather(*coros_or_futures, loop=None, return_exceptions=False):
# If gather is being cancelled we must propagate the
# cancellation regardless of *return_exceptions* argument.
# See issue 32684.
exc = exceptions.CancelledError(''
if fut._cancel_message is None else fut._cancel_message)
exc = fut._make_cancelled_error()
outer.set_exception(exc)
else:
outer.set_result(results)