[Async-sig] Some thoughts on asynchronous API design in a post-async/await world

[Glyph Lefkowitz]

> On Nov 7, 2016, at 11:08 AM, Yury Selivanov <yselivanov at gmail.com> wrote:
> 
> [..]
>> Sorry, this was a bit tongue in cheek.  This was something I said to Guido at the *very* beginning of Tulip development, when asked about mistakes Twisted has made: "don't have a global event loop, you'll never get away from it".
>> 
>> I still think getting rid of a global loop would always be an improvement, although I suspect it's too late at this point.  `await current_event_loop()` might make more sense in Asyncio as that's not really "global", similar to Curio's trap of the same design; however, I assume that this was an intentional design disagreement for a reason and I don't see that reason as having changed (as Yury indicates).
> 
> The latest update of get_event_loop is a step in the right direction. At least now we can document the best practices:
> 
> 1. Have one “main” coroutine to bootstrap/run your program;
> 
> 2. Don’t design APIs that accept the loop parameter; instead design coroutine-first APIs and use get_event_loop in your library if you absolutely need the loop.
> 
> 3. I want to add “asyncio.main(coro)” function, which would create the loop, run the “coro” coroutine, and correctly clean everything up.
> 
> What you propose, IIUC is a step further:
> 
> * Deprecate get_event_loop();
> 
> * Add “current_event_loop()” coroutine.
> 
> This will enforce (1) and (2), making asyncio library devs/users to focus more on coroutines and async/await.
> 
> Am I understanding this all correctly?

Yep.  It's not so much making users focus more on coroutines, as having a way to pass a loop to a coroutine that is explicit (the coro needs to be scheduled on a loop already, so the binding has been explicitly specified) but unobtrusive.

-glyph
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