[PATCH] py3: catch StopIteration from next() in generatorset

[Sean Farley]

Martin von Zweigbergk <martinvonz at google.com> writes:

> On Tue, Jun 20, 2017 at 3:24 PM, Martin von Zweigbergk
> <martinvonz at google.com> wrote:
>> On Tue, Jun 20, 2017 at 2:53 PM, Sean Farley <sean at farley.io> wrote:
>>> Martin von Zweigbergk via Mercurial-devel
>>> <mercurial-devel at mercurial-scm.org> writes:
>>>
>>>> # HG changeset patch
>>>> # User Martin von Zweigbergk <martinvonz at google.com>
>>>> # Date 1497992441 25200
>>>> #      Tue Jun 20 14:00:41 2017 -0700
>>>> # Node ID f86d21c457209f5f5a139bcc808be33fbd930424
>>>> # Parent  0906385672d754f13a512fe70759f0463a069f1e
>>>> py3: catch StopIteration from next() in generatorset
>>>>
>>>> IIUC, letting the StopIteration through would not cause any bugs, but
>>>> not doing it makes the test-py3-commands.t pass.
>>>>
>>>> I have also diligently gone through all uses of next() in our code
>>>> base. They either:
>>>>
>>>>  * are not called from a generator
>>>>  * pass a default value to next()
>>>>  * catch StopException
>>>>  * work on infinite iterators
>>>>  * request a fixed number of items that matches the generated number
>>>>  * are about batching in wireproto which I didn't quite follow
>>>>
>>>> I'd appreciate if Augie or someone else could take a look at the
>>>> wireproto batching and convince themselves that the next(batchable)
>>>> calls there will not raise a StopIteration.
>>>
>>> I was just thinking of doing something like this. Shouldn't we just
>>> 'return None' in Mercurial instead of 'raise StopIteration'?
>>
>> I thought "return" was just short for "return None". Are you just
>> saying that we prefer "return None" in Mercurial? Should I send a v2?
>
> Oh, never mind. You're of course talking about not using "raise
> StopIteration" in general, not specifically about this patch. Yes,
> that's probably true. I think there were just a few more cases of
> "raise StopIteration" to deal with.
>
> Anyway, that won't fix this case, because next() itself raise StopIteration.

Seems I've had two race conditions today. Ah, I see. I'll be quiet now :-)
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