On Fri, Oct 13, 2017 at 3:25 AM, Nick Coghlan <[email protected]> wrote:
[..]
> However, considering that coroutines are almost always instantiated at the
> point where they're awaited, I do concede that creation time context capture
> would likely also work out OK for the coroutine case, which would leave
> contextlib.contextmanager as the only special case (and it would turn off
> both creation-time context capture *and* context isolation).
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.
Yury
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