bpo-35409: Ignore GeneratorExit in async_gen_athrow_throw

[vxgmichel]

Ignore GeneratorExit exceptions when throwing an exception into the aclose coroutine of an asynchronous generator.

https://bugs.python.org/issue35409

Automerge-Triggered-By: @asvetlov

[vxgmichel]

Corresponding PR on pypy: https://bitbucket.org/pypy/pypy/pull-requests/655

[1st1]

Can you double check if regular generators have the same bahavior before we merge?

[vxgmichel]

@1st1

Can you double check if regular generators have the same behavior before we merge?

Well, I don't think this behavior applies to regular generators. The closest thing I could think of is:

>>> def gen():
...     try:
...         yield
...     finally:
...         yield
... 
>>> g = gen()
>>> g.send(None)
>>> g.close()

which produces:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: generator ignored GeneratorExit

Also note that the chunk of code added to async_gen_athrow_throw is directly taken from async_gen_athrow_send. A bit of refactoring might be required, although I don't feel comfortable enough to do it myself. A similar refactoring has been done in pypy: see the handle_error method which is used by both the send and throw methods of the athrow coroutine.

[vxgmichel]

Just pinging, as it turns out to be a blocking issue for the aiostream library :)

[1st1]

Andrew, can you take a look at this too?

[asvetlov]

Is it urgent?
I'll have time next week only after finishing my business trip.

[1st1]

I guess since we missed the RC1 for this it's no longer urgent. But please look at this as soon as you can. I'd like to hear your opinion.

[vxgmichel]

Hi all, I'm just pinging again as I would really like to have this issue fixed :)

[asvetlov]

LGTM

[miss-islington]

Sorry, I can't merge this PR. Reason: Base branch was modified. Review and try the merge again..

[miss-islington]

Thanks @vxgmichel for the PR 🌮🎉.. I'm working now to backport this PR to: 3.7, 3.8.
🐍🍒⛏🤖

[miss-islington]

I'm having trouble backporting to 3.8. Reason: 'Error 110 while writing to socket. Connection timed out.'. Please retry by removing and re-adding the needs backport to 3.8 label.

[bedevere-bot]

GH-17257 is a backport of this pull request to the 3.7 branch.

[miss-islington]

Thanks @vxgmichel for the PR 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-bot]

GH-17258 is a backport of this pull request to the 3.8 branch.

[asvetlov]

Thanks!