unusual behaviour in asyncio.TaskGroup in the presence of GeneratorExit, StopIteration, KeyboardInterrupt and SystemExit
Open
Nobody has claimed this yet.
3.11
3.12
topic-asyncio
type-bug
- Dominant language
- Python
- Stars
- 77.2k
- Forks
- 36k
- PR merge metrics
- PR metrics pending
Description
import gc
import asyncio
import logging
logger = logging.getLogger(__name__)
async def keyboard_interrupt():
raise KeyboardInterrupt
async def system_exit():
raise SystemExit
async def task_groups():
async with asyncio.TaskGroup() as tg:
tg.create_task(system_exit())
tg.create_task(keyboard_interrupt())
loop = asyncio.SelectorEventLoop()
task = loop.create_task(task_groups())
while not task.done():
try:
loop.run_until_complete(asyncio.sleep(0))
except (SystemExit, KeyboardInterrupt) as e:
print(f"{e=}")
print(f"{task=} {task.exception()=}")
loop.close()
print("#######################################################")
async def gen_exit():
async with asyncio.TaskGroup() as tg:
await asyncio.get_running_loop().create_future()
loop = asyncio.SelectorEventLoop()
task = loop.create_task(gen_exit())
loop.run_until_complete(asyncio.sleep(0))
del task
gc.collect()
print("#######################################################")
gives the following output on 3.12:
e=SystemExit()
e=KeyboardInterrupt()
e=SystemExit()
task=<Task finished name='Task-1' coro=<task_groups() done, defined at /home/graingert/projects/cpython/demo.py:14> exception=SystemExit()> task.exception()=SystemExit()
#######################################################
Exception ignored in: <coroutine object gen_exit at 0x7fd62350cd60>
Traceback (most recent call last):
File "/home/graingert/projects/cpython/demo.py", line 37, in gen_exit
async with asyncio.TaskGroup() as tg:
File "/home/graingert/projects/cpython/Lib/asyncio/taskgroups.py", line 134, in __aexit__
raise me from None
BaseExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
Task was destroyed but it is pending!
task: <Task pending name='Task-7' coro=<gen_exit() done, defined at /home/graingert/projects/cpython/demo.py:36> wait_for=<Future pending cb=[Task.task_wakeup()]>>
#######################################################
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Run the supplied Python 3.12 reproducer first, then inspect Lib/asyncio/taskgroups.py around TaskGroup.aexit and the asyncio task creation calls. Trace the GeneratorExit, StopIteration, KeyboardInterrupt, and SystemExit paths and establish the expected behavior before adding coverage; the issue does not yet specify the desired outcome.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100