On Fri, Oct 13, 2017 at 1:45 PM, Ethan Furman email@example.com wrote:
On 10/13/2017 09:48 AM, Steve Dower wrote: >
On 13Oct2017 0941, Yury Selivanov wrote:
Actually, capturing context at the moment of coroutine creation (in PEP 550 v1 semantics) will not work at all. Async context managers will break.
class AC: async def __aenter__(self): pass
^ If the context is captured when coroutines are instantiated, __aenter__ won't be able to set context variables and thus affect the code it wraps. That's why coroutines shouldn't capture context when created, nor they should isolate context. It's a job of async Task.
Then make __aenter__/__aexit__ when called by "async with" an exception to the normal semantics?
It seems simpler to have one specially named and specially called function be special, rather than make the semantics more complicated for all functions.
It's not possible to special case __aenter__ and __aexit__ reliably (supporting wrappers, decorators, and possible side effects).
I still don't understand what Steve means by "more usable", to be honest.