asyncio: C implemeted Future cause Tornado test fail

[methane]

BPO	28430
Nosy	@gvanrossum, @terryjreedy, @methane, @socketpair, @1st1
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	future-iter-send.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/methane'
closed_at = <Date 2016-10-25.10:31:07.366>
created_at = <Date 2016-10-13.12:43:15.175>
labels = ['type-bug', '3.7', 'expert-asyncio']
title = 'asyncio: C implemeted Future cause Tornado test fail'
updated_at = <Date 2017-03-31.16:36:16.006>
user = 'https://github.com/methane'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:16.006>
actor = 'dstufft'
assignee = 'methane'
closed = True
closed_date = <Date 2016-10-25.10:31:07.366>
closer = 'methane'
components = ['asyncio']
creation = <Date 2016-10-13.12:43:15.175>
creator = 'methane'
dependencies = []
files = ['45165']
hgrepos = []
issue_num = 28430
keywords = ['patch']
message_count = 9.0
messages = ['278569', '278686', '279095', '279104', '279150', '279382', '279388', '279404', '279406']
nosy_count = 6.0
nosy_names = ['gvanrossum', 'terry.reedy', 'methane', 'socketpair', 'python-dev', 'yselivanov']
pr_nums = ['552']
priority = 'high'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue28430'
versions = ['Python 3.6', 'Python 3.7']

[methane]

https://travis-ci.org/tornadoweb/tornado/jobs/167252979

[methane]

Another test failure is reported.

I have setup a 3.6 build on Travis of our project GNS3 and it seem to fail.
https://travis-ci.org/GNS3/gns3-server/builds/167703118

[methane]

pure Python Future.__iter__ don't use what yield-ed.

    def __iter__(self):
        if not self.done():
            self._asyncio_future_blocking = True
            yield self  # This tells Task to wait for completion.
        assert self.done(), "yield from wasn't used with future"
        return self.result()  # May raise too.

I felt no-None value is sent by iter.send(val) wasn't make sense.
But Tornado did it (maybe, for compatibility to Tornado's generator.)

So this patch ignores when non-None value is passed.
Additionally, I moved NEWS entry about C Future from "core and builtin"
section to "library" section.

[methane]

Test failure in GNS3 seems not relating to this.
It may be fixed via bpo-28492, maybe.

[1st1]

The patch looks good. 2 things:

• It appears it also touches Misc/NEWS a bit too much. Please make sure to not to commit that.

• I'd also add a comment explaining why we ignore values passed to FI.send() and simply send None. The reason is how Future.__iter__ is designed:

   class Future:
      def __iter__(self):
        if not self.done():
            self._asyncio_future_blocking = True
            yield self  # This tells Task to wait for completion.
        assert self.done(), "yield from wasn't used with future"
        return self.result()  # May raise too.

^-- Future.__iter__ doesn't care about values that are pushed to the generator, it just returns "self.result()".

[python-dev]

New changeset b471447352ac by INADA Naoki in branch '3.6':
Issue bpo-28430: Fix iterator of C implemented asyncio.Future doesn't
https://hg.python.org/cpython/rev/b471447352ac

New changeset bd141ec2973a by INADA Naoki in branch 'default':
Issue bpo-28430: Fix iterator of C implemented asyncio.Future doesn't
https://hg.python.org/cpython/rev/bd141ec2973a

[methane]

• It appears it also touches Misc/NEWS a bit too much. Please make sure to not to commit that.

I wont to move move this entry from "Core and Builtins" section to "Library" section:

• Issue bpo-26081: Added C implementation of asyncio.Future.
  Original patch by Yury Selivanov.

May I do it?

[terryjreedy]

+- Issue bpo-28430: Fix iterator of C implemented asyncio.Future doesn't accept

+ non-None value is passed to it.send(val).

This NEWS entry is not a coherent English sentence. Please revise. I don't understand it well enough to suggest a revision, but would review a replacement.

[methane]

I'm sorry about my bad English.

Fix iterator of C implemented asyncio.Future

This meant:

fut = asyncio.Future()  # C implemented version of asyncio.Future
it = iter(fut)  # Iterator of it
it.send(42)     # raised TypeError before. It was not compatible with Python version of asyncio.Future