bpo-31033: Add a msg argument to Future.cancel() and Task.cancel() (GH-19979)
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index f5de1a2..a3a0a33 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -230,7 +230,7 @@
"""
return base_tasks._task_print_stack(self, limit, file)
- def cancel(self):
+ def cancel(self, msg=None):
"""Request that this task cancel itself.
This arranges for a CancelledError to be thrown into the
@@ -254,13 +254,14 @@
if self.done():
return False
if self._fut_waiter is not None:
- if self._fut_waiter.cancel():
+ if self._fut_waiter.cancel(msg=msg):
# Leave self._fut_waiter; it may be a Task that
# catches and ignores the cancellation so we may have
# to cancel it again later.
return True
# It must be the case that self.__step is already scheduled.
self._must_cancel = True
+ self._cancel_message = msg
return True
def __step(self, exc=None):
@@ -269,7 +270,8 @@
f'_step(): already done: {self!r}, {exc!r}')
if self._must_cancel:
if not isinstance(exc, exceptions.CancelledError):
- exc = exceptions.CancelledError()
+ exc = exceptions.CancelledError(''
+ if self._cancel_message is None else self._cancel_message)
self._must_cancel = False
coro = self._coro
self._fut_waiter = None
@@ -287,11 +289,15 @@
if self._must_cancel:
# Task is cancelled right before coro stops.
self._must_cancel = False
- super().cancel()
+ super().cancel(msg=self._cancel_message)
else:
super().set_result(exc.value)
- except exceptions.CancelledError:
- super().cancel() # I.e., Future.cancel(self).
+ 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).
except (KeyboardInterrupt, SystemExit) as exc:
super().set_exception(exc)
raise
@@ -319,7 +325,8 @@
self.__wakeup, context=self._context)
self._fut_waiter = result
if self._must_cancel:
- if self._fut_waiter.cancel():
+ if self._fut_waiter.cancel(
+ msg=self._cancel_message):
self._must_cancel = False
else:
new_exc = RuntimeError(
@@ -716,12 +723,12 @@
self._children = children
self._cancel_requested = False
- def cancel(self):
+ def cancel(self, msg=None):
if self.done():
return False
ret = False
for child in self._children:
- if child.cancel():
+ if child.cancel(msg=msg):
ret = True
if ret:
# If any child tasks were actually cancelled, we should
@@ -780,7 +787,8 @@
# Check if 'fut' is cancelled first, as
# 'fut.exception()' will *raise* a CancelledError
# instead of returning it.
- exc = exceptions.CancelledError()
+ exc = exceptions.CancelledError(''
+ if fut._cancel_message is None else fut._cancel_message)
outer.set_exception(exc)
return
else:
@@ -799,7 +807,9 @@
# Check if 'fut' is cancelled first, as
# 'fut.exception()' will *raise* a CancelledError
# instead of returning it.
- res = exceptions.CancelledError()
+ res = exceptions.CancelledError(
+ '' if fut._cancel_message is None else
+ fut._cancel_message)
else:
res = fut.exception()
if res is None:
@@ -810,7 +820,9 @@
# If gather is being cancelled we must propagate the
# cancellation regardless of *return_exceptions* argument.
# See issue 32684.
- outer.set_exception(exceptions.CancelledError())
+ exc = exceptions.CancelledError(''
+ if fut._cancel_message is None else fut._cancel_message)
+ outer.set_exception(exc)
else:
outer.set_result(results)