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bpo-46829: Deprecate passing a message into Future.cancel() and Task.cancel() (GH-31840) 

After a long deliberation we ended up feeling that the message argument for Future.cancel(), added in 3.9, was a bad idea, so we're deprecating it in 3.11 and plan to remove it in 3.13.
This commit is contained in:
Andrew Svetlov 2022-03-23 17:43:05 +02:00 committed by GitHub
parent 624e3986fb
commit 0360e9f346
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9 changed files with 106 additions and 17 deletions
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10
Doc/library/asyncio-future.rst
View File

@ -196,6 +196,11 @@ Future Object
.. versionchanged:: 3.9
Added the *msg* parameter.
.. deprecated-removed:: 3.11 3.14
*msg* parameter is ambiguous when multiple :meth:`cancel`
are called with different cancellation messages.
The argument will be removed.
.. method:: exception()
Return the exception that was set on this Future.
@ -276,3 +281,8 @@ the Future has a result::
- :meth:`asyncio.Future.cancel` accepts an optional ``msg`` argument,
but :func:`concurrent.futures.cancel` does not.
.. deprecated-removed:: 3.11 3.14
*msg* parameter is ambiguous when multiple :meth:`cancel`
are called with different cancellation messages.
The argument will be removed.

6
Doc/library/asyncio-task.rst
View File

@ -810,8 +810,10 @@ Task Object
.. versionchanged:: 3.9
Added the *msg* parameter.
.. versionchanged:: 3.11
The ``msg`` parameter is propagated from cancelled task to its awaiter.
.. deprecated-removed:: 3.11 3.14
*msg* parameter is ambiguous when multiple :meth:`cancel`
are called with different cancellation messages.
The argument will be removed.
.. _asyncio_example_task_cancel:

6
Lib/asyncio/futures.py
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@ -8,6 +8,7 @@ import concurrent.futures
import contextvars
import logging
import sys
import warnings
from types import GenericAlias
from . import base_futures
@ -150,6 +151,11 @@ class Future:
change the future's state to cancelled, schedule the callbacks and
return True.
"""
if msg is not None:
warnings.warn("Passing 'msg' argument to Future.cancel() "
"is deprecated since Python 3.11, and "
"scheduled for removal in Python 3.14.",
DeprecationWarning, stacklevel=2)
self.__log_traceback = False
if self._state != _PENDING:
return False

5
Lib/asyncio/tasks.py
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@ -207,6 +207,11 @@ class Task(futures._PyFuture): # Inherit Python Task implementation
This also increases the task's count of cancellation requests.
"""
if msg is not None:
warnings.warn("Passing 'msg' argument to Task.cancel() "
"is deprecated since Python 3.11, and "
"scheduled for removal in Python 3.14.",
DeprecationWarning, stacklevel=2)
self._log_traceback = False
if self.done():
return False

12
Lib/test/test_asyncio/test_futures.py
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@ -228,14 +228,22 @@ class BaseFutureTests:
self.assertTrue(hasattr(f, '_cancel_message'))
self.assertEqual(f._cancel_message, None)
f.cancel('my message')
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
f.cancel('my message')
with self.assertRaises(asyncio.CancelledError):
self.loop.run_until_complete(f)
self.assertEqual(f._cancel_message, 'my message')
def test_future_cancel_message_setter(self):
f = self._new_future(loop=self.loop)
f.cancel('my message')
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
f.cancel('my message')
f._cancel_message = 'my new message'
self.assertEqual(f._cancel_message, 'my new message')

8
Lib/test/test_asyncio/test_taskgroups.py
View File

@ -191,12 +191,10 @@ class TestTaskGroup(unittest.IsolatedAsyncioTestCase):
await asyncio.sleep(0.1)
self.assertFalse(r.done())
r.cancel("test")
r.cancel()
with self.assertRaises(asyncio.CancelledError) as cm:
await r
self.assertEqual(cm.exception.args, ('test',))
self.assertEqual(NUM, 5)
async def test_taskgroup_07(self):
@ -253,12 +251,10 @@ class TestTaskGroup(unittest.IsolatedAsyncioTestCase):
await asyncio.sleep(0.1)
self.assertFalse(r.done())
r.cancel("test")
r.cancel()
with self.assertRaises(asyncio.CancelledError) as cm:
await r
self.assertEqual(cm.exception.args, ('test',))
async def test_taskgroup_09(self):
t1 = t2 = None

54
Lib/test/test_asyncio/test_tasks.py
View File

@ -113,7 +113,11 @@ class BaseTaskTests:
self.assertTrue(hasattr(t, '_cancel_message'))
self.assertEqual(t._cancel_message, None)
t.cancel('my message')
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
t.cancel('my message')
self.assertEqual(t._cancel_message, 'my message')
with self.assertRaises(asyncio.CancelledError) as cm:
@ -125,7 +129,11 @@ class BaseTaskTests:
async def coro():
pass
t = self.new_task(self.loop, coro())
t.cancel('my message')
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
t.cancel('my message')
t._cancel_message = 'my new message'
self.assertEqual(t._cancel_message, 'my new message')
@ -582,7 +590,14 @@ class BaseTaskTests:
async def coro():
task = self.new_task(loop, sleep())
await asyncio.sleep(0)
task.cancel(*cancel_args)
if cancel_args not in ((), (None,)):
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
task.cancel(*cancel_args)
else:
task.cancel(*cancel_args)
done, pending = await asyncio.wait([task])
task.result()
@ -616,7 +631,14 @@ class BaseTaskTests:
async def coro():
task = self.new_task(loop, sleep())
await asyncio.sleep(0)
task.cancel(*cancel_args)
if cancel_args not in ((), (None,)):
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
task.cancel(*cancel_args)
else:
task.cancel(*cancel_args)
done, pending = await asyncio.wait([task])
task.exception()
@ -639,10 +661,17 @@ class BaseTaskTests:
fut.set_result(None)
await asyncio.sleep(10)
def cancel(task, msg):
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
task.cancel(msg)
async def coro():
inner_task = self.new_task(loop, sleep())
await fut
loop.call_soon(inner_task.cancel, 'msg')
loop.call_soon(cancel, inner_task, 'msg')
try:
await inner_task
except asyncio.CancelledError as ex:
@ -668,7 +697,11 @@ class BaseTaskTests:
async def coro():
task = self.new_task(loop, sleep())
# We deliberately leave out the sleep here.
task.cancel('my message')
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
task.cancel('my message')
done, pending = await asyncio.wait([task])
task.exception()
@ -2029,7 +2062,14 @@ class BaseTaskTests:
async def main():
qwe = self.new_task(loop, test())
await asyncio.sleep(0.2)
qwe.cancel(*cancel_args)
if cancel_args not in ((), (None,)):
with self.assertWarnsRegex(
DeprecationWarning,
"Passing 'msg' argument"
):
qwe.cancel(*cancel_args)
else:
qwe.cancel(*cancel_args)
await qwe
try:

2
Misc/NEWS.d/next/Core and Builtins/2022-03-12-21-07-21.bpo-46829.cpGoPV.rst Normal file
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@ -0,0 +1,2 @@
Deprecate passing a message into :meth:`asyncio.Future.cancel` and
:meth:`asyncio.Task.cancel`

20
Modules/_asynciomodule.c
View File

@ -1096,6 +1096,16 @@ static PyObject *
_asyncio_Future_cancel_impl(FutureObj *self, PyObject *msg)
/*[clinic end generated code: output=3edebbc668e5aba3 input=925eb545251f2c5a]*/
{
if (msg != Py_None) {
if (PyErr_WarnEx(PyExc_DeprecationWarning,
"Passing 'msg' argument to Future.cancel() "
"is deprecated since Python 3.11, and "
"scheduled for removal in Python 3.14.",
2))
{
return NULL;
}
}
ENSURE_FUTURE_ALIVE(self)
return future_cancel(self, msg);
}
@ -2176,6 +2186,16 @@ static PyObject *
_asyncio_Task_cancel_impl(TaskObj *self, PyObject *msg)
/*[clinic end generated code: output=c66b60d41c74f9f1 input=7bb51bf25974c783]*/
{
if (msg != Py_None) {
if (PyErr_WarnEx(PyExc_DeprecationWarning,
"Passing 'msg' argument to Task.cancel() "
"is deprecated since Python 3.11, and "
"scheduled for removal in Python 3.14.",
2))
{
return NULL;
}
}
self->task_log_tb = 0;
if (self->task_state != STATE_PENDING) {