bpo-34790: Implement deprecation of passing coroutines to asyncio.wait()

[aeros]

/cc @1st1 @asvetlov

https://bugs.python.org/issue34790

[aeros]

Adding a DO-NOT-MERGE label for now. Although the deprecation seems to be properly implemented, I have to refactor the existing tests with self.assertWarns(DeprecationWarning) where coroutines are being passed to asyncio.wait().

[aeros]

I have to refactor the existing tests with self.assertWarns(DeprecationWarning) where coroutine objects are being passed to asyncio.wait()

Done, removing DO-NOT-MERGE label.

[aeros:~/repos/aeros-cpython]$ ./python -W error -m test test_asyncio
0:00:00 load avg: 0.33 Run tests sequentially
0:00:00 load avg: 0.33 [1/1] test_asyncio
test_asyncio passed in 43.2 sec

== Tests result: SUCCESS ==

1 test OK.

Total duration: 43.2 sec
Tests result: SUCCESS

[asvetlov]

LGTM.
The PR should not be backported to 3.8, right?
It raises new deprecations that were absent in 3.8.0; adding them in 3.8.1 is confusing.

[aeros]

@asvetlov

The PR should not be backported to 3.8, right?

Yep, that's why I did this one separately from #16975, which only fixed the 3.8 whatsnew entry based on Yury's suggestion. Otherwise, the changes would've been combined into the same PR.

It raises new deprecations that were absent in 3.8.0; adding them in 3.8.1 is confusing.

Agreed, I'm starting to realize that we should try to avoid implementing significant deprecations partway through a major version (3.x) when possible. It would more likely comely across to users as a surprise and lead to some confusion rather than being overly helpful. For example, if users have already ran their tests with warnings enabled and resolved any deprecation warnings for 3.8.0, I don't think it would be a great experience for them to encounter a bunch of new ones in 3.8.1.

[aeros]

@1st1 @asvetlov What are your thoughts on updating the documentation for asyncio.as_completed() to mention that an iterator of completed coroutine objects is returned when coroutine objects are passed to fs? I don't think this behavior is very obvious.

As a result, I would like to structure it similarly to the documentation for asyncio.ensure_future(), where the behavior for Futures, Tasks, and coroutine objects are explicitly specified.

For more context, see #16977 (comment).

[aeros]

@asvetlov @1st1 Is there anything else that needs to added to this PR or are we just waiting for a final review?

[asvetlov]

Thanks.
Regarding mentioned docs for as_completed() and ensure_future() -- please let's discuss in separate issues.
I quite don't follow your proposals, sorry.

[aeros]

Regarding mentioned docs for as_completed() and ensure_future() -- please let's discuss in separate issues.

Yeah, I'll have to spend more time fleshing those ideas out and consider if the proposals might be worthwhile.

Thanks!