[Python-Dev] PEP 492 and types.coroutine

[Guido van Rossum]

Ethan, at this point your continued arguing is not doing anybody anything
good. Please stop.

On Sat, May 2, 2015 at 2:31 PM, Ethan Furman <ethan at stoneleaf.us> wrote:

> On 05/02, Yury Selivanov wrote:
> > On 2015-05-02 2:14 PM, Ethan Furman wrote:
> >> On 05/02, Yury Selivanov wrote:
> >>> On 2015-05-02 1:04 PM, Ethan Furman wrote:
>
> >> And yet in current asyncio code, random generators can be accepted, and
> not
> >> even the current asyncio.coroutine wrapper can gaurantee that the
> generator
> >> is a coroutine in fact.
>
> > This is a flaw in the current Python that we want to fix.
>
> Your "fix" doesn't fix it.  I can decorate a non-coroutine generator with
> type.coroutine and it will still be broken and a bug in my code.
>
>
> >> For that matter, even the new types.coroutine cannot gaurantee that the
> >> returned object is a coroutine and not a generator -- so basically it's
> just
> >> there to tell the compiler, "yeah, I really know what I'm doing, shut
> up and
> >> do what I asked."
> >
> > Well, why would you use it on some generator that is not
> > a generator-based coroutine?
>
> I wouldn't, that would be a bug; but decorating a wrong type of generator
> is
> still a bug, and type.coroutine has not fixed that bug.
>
> It's worse than mandatory typing because it can't even check that what I
> have
> declared is true.
>
>
> >> So either way, nothing has been added besides a mandatory boiler-plate
> >> requirement.
> >
> > It's not nothing; it's backwards compatibility.  Please read
> > https://www.python.org/dev/peps/pep-0492/#await-expression
>
> I have read it, more than once.  If you lift the (brand-new) requirement
> that a
> generator must be decorated, then type.coroutine becomes optional (no more
> useful, just optional).  It is not a current requirement that coroutine
> generators be decorated.
>
> --
> ~Ethan~
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-- 
--Guido van Rossum (python.org/~guido)
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