[Python-Dev] PEP 492 and types.coroutine
ethan at stoneleaf.us
Sat May 2 23:31:37 CEST 2015
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
> It's not nothing; it's backwards compatibility. Please read
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.
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