Add `msg` to `task.cancel()` method to allow distinguish the source of cancellation

[achimnol]

How about adding msg argument to task.cancel()?

TL;DR:

def _on_timeout(self, task: "asyncio.Task[None]") -> None:
    task.cancel(msg="timeout")  # <--- add the reason of cancellation
    self._state = _State.TIMEOUT
    # drop the reference early
    self._timeout_handler = None

This would be useful to distinguish the reason of cancellation in library's user programs.

[ljluestc]

import asyncio

class CustomTask(asyncio.Task):
def cancel(self, msg=None):
self._msg = msg
super().cancel()

def _on_timeout(self, task: "asyncio.Task[None]") -> None:
task.cancel(msg="timeout") # Adding a custom reason for cancellation
self._state = _State.TIMEOUT
# Drop the reference early
self._timeout_handler = None

Replace asyncio.Task with CustomTask wherever you want to use it

async def main():
loop = asyncio.get_event_loop()
task = loop.create_task(async_func())
await asyncio.sleep(1)
task.cancel("custom_reason")

loop = asyncio.get_event_loop()
loop.run_until_complete(main())
loop.close()

[asvetlov]

Version 5.0+ works exactly as asyncio built-in does, nothing to do here.