Open
Description
I am aware of the issues with cleaning up async iterators, PEP 533 and the need for aclosing. However, if a closing is not used, which I overlook frequently, things can really blow up in your face:
import trio
async def gen_with_task():
async with trio.open_nursery() as n:
n.start_soon(trio.sleep_forever)
while True:
await trio.sleep(1)
yield 1
async def main():
async for f in gen_with_task():
raise ValueError()
trio.run(main)gives me:
Exception ignored in: <async_generator object gen_with_task at 0x10c7857b8>
RuntimeError: async generator ignored GeneratorExit
Traceback (most recent call last):
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 1229, in run
result = run_impl(runner, async_fn, args)
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 1357, in run_impl
runner.task_exited(task, final_result)
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 852, in task_exited
self.tasks.remove(task)
KeyError: <Task '__main__.main' at 0x10c72c668>
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "triotest.py", line 14, in <module>
trio.run(main)
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 1235, in run
) from exc
trio.TrioInternalError: internal error in trio - please file a bug!
Exception ignored in: <coroutine object _AsyncGeneratorContextManager.__aexit__ at 0x10c78f648>
Traceback (most recent call last):
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_util.py", line 84, in __aexit__
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_util.py", line 14, in __aexit__
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_impl.py", line 308, in aclose
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_impl.py", line 277, in athrow
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_impl.py", line 290, in _do_it
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_impl.py", line 197, in __next__
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/async_generator/_impl.py", line 209, in _invoke
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 311, in open_nursery
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/contextlib.py", line 130, in __exit__
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 198, in open_cancel_scope
File "/Users/michael/.pyenv/versions/3.7.0/lib/python3.7/site-packages/trio/_core/_run.py", line 157, in _remove_task
KeyError: <Task '__main__.main' at 0x10c72c668>
Note that in addition to the internal trio exceptions, the original cause is not shown at all. This happens when the async generator had a task running in a nursery.
Maybe there is no way to handle this better - I can't tell, this is above my paygrade! But in case there is a way to show a clearer error message, I think it might be worth it.