`TaskGroup` propagates `CancelledError` rather than a `MultiError` on exception

[bdowning]

See the following snippet:

import asyncio
import aiotools

async def error():
    await asyncio.sleep(1)
    raise Exception("bad stuff")

async def main():
    try:
        async with aiotools.TaskGroup() as tg:
            tg.create_task(error())
            await asyncio.sleep(5)
    except Exception as e:
        print(f"Got inner {repr(e)}")
        raise

try:
    asyncio.run(main())
except BaseException as e:
    print(f"Got outer {repr(e)}")

Got outer CancelledError()

Is this expected behavior? It feels wrong, since a) it ate an exception and b) the task wasn't actually cancelled.

This is Python 3.9 and aiotools 1.4.0.

[achimnol]

Let's inspect how python/cpython#31270 handles this...

[achimnol]

Also refer https://bugs.python.org/issue46771

[achimnol]

I have tested your code with asyncio.TaskGroup introduced in Python 3.11 development version.

Got inner ExceptionGroup('unhandled errors in a TaskGroup', [Exception('bad stuff')])
Got outer ExceptionGroup('unhandled errors in a TaskGroup', [Exception('bad stuff')])

With aiotools.TaskGroup,

Got outer CancelledError()

It seems to have some problem, definitely. I'll look into more.