Yury Selivanov added the comment: > 2) Awaitable.register(Coroutine) > I think this is incorrect. A Coroutine is not Awaitable unless it also > implements "__await__". How else should it be awaited?
It *is* correct, see PEP 492. Awaitable is either a coroutine *or* an object with an __await__ method. Generally, being an awaitable means that the object can be used in "await" expression. > 3) > I propose to use this wrapping code as a fallback for types.coroutine() in > the case that a Generator (ABC) is passed instead of a generator (yield): Just implement tp_await/__await__ for coroutine-like objects coming from C-API or Cython. In general, iteration protocol is still the foundation for Future-like objects, so there is nothing wrong with this. Generator ABC isn't supposed to be used with "await" expression. > 4) > > def test_func_2(self): > async def foo(): > raise StopIteration > > with self.assertRaisesRegex( > RuntimeError, "generator raised StopIteration"): > > run_async(foo()) > Why is this actually necessary? I'm aware that it's also mentioned in the > PEP, but is there an actual reason why a coroutine should behave the same as > a generator here? Is it just an implementation detail for legacy reasons > because generators and coroutines happen to share the same type > implementation? (I don't think they need to, BTW.) Coroutines are implemented on top of generators. Until we clearly separate them (in 3.6?) I don't think we should allow coroutines to bubble up StopIteration. > 5) > def test_func_8(self): > @types.coroutine > def bar(): > return (yield from foo()) > > async def foo(): > return 'spam' > > self.assertEqual(run_async(bar()), ([], 'spam') ) > > I find it surprising that this works at all. Yield-from iterates, and a > coroutine is not supposed to be iterable, only awaitable (at least, that's > what all error messages tell me when I try it). So why should "yield from" > work on them? What if foo() was not an Iterable but a Coroutine? Should > "yield from" then call "__await__" on it internally? I would find that > *really* surprising, but given the above, I think it would be necessary to > achieve consistency. This is a special backwards-compatibility thing. In general, generators cannot yield-from coroutines (unless they are decorated with @types.coroutine). ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue24017> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
