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

Lib/asyncio/futures.py

@@ -8,6 +8,7 @@
 import contextvars
 import logging
 import sys
+import warnings
 from types import GenericAlias
 
 from . import base_futures
@@ -153,6 +154,11 @@ def cancel(self, msg=None):
  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

Lib/asyncio/tasks.py

@@ -201,6 +201,11 @@ def cancel(self, msg=None):
 
  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

Lib/test/test_asyncio/test_futures.py

@@ -228,14 +228,22 @@ def test_future_cancel_message_getter(self):
  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')
 

Lib/test/test_asyncio/test_taskgroups.py

@@ -190,7 +190,11 @@ async def runner():
  await asyncio.sleep(0.1)
 
  self.assertFalse(r.done())
- r.cancel("test")
+ with self.assertWarnsRegex(
+ DeprecationWarning,
+ "Passing 'msg' argument"
+ ):
+ r.cancel("test")
  with self.assertRaises(asyncio.CancelledError) as cm:
  await r
 
@@ -252,7 +256,11 @@ async def runner():
  await asyncio.sleep(0.1)
 
  self.assertFalse(r.done())
- r.cancel("test")
+ with self.assertWarnsRegex(
+ DeprecationWarning,
+ "Passing 'msg' argument"
+ ):
+ r.cancel("test")
  with self.assertRaises(asyncio.CancelledError) as cm:
  await r
 

Lib/test/test_asyncio/test_tasks.py

@@ -121,7 +121,11 @@ async def coro():
  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:
@@ -133,7 +137,11 @@ def test_task_cancel_message_setter(self):
  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')
 
@@ -590,7 +598,14 @@ async def sleep():
  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()
 
@@ -624,7 +639,14 @@ async def sleep():
  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()
 
@@ -647,10 +669,17 @@ async def sleep():
  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:
@@ -676,7 +705,11 @@ async def sleep():
  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()
 
@@ -2326,7 +2359,14 @@ async def test():
  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:

Misc/NEWS.d/next/Core and Builtins/2022-03-12-21-07-21.bpo-46829.cpGoPV.rst

@@ -0,0 +1,2 @@
+Deprecate passing a message into :meth:`asyncio.Future.cancel` and
+:meth:`asyncio.Task.cancel`

Modules/_asynciomodule.c

@@ -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);
 }
@@ -2199,6 +2209,16 @@ 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) {