[issue29271] Task.current_task(None) returns unexpected result

[Yury Selivanov]

New submission from Yury Selivanov:

Quoting Alberto Berdi from python-tulip mailing list:

working with the Python 3.6 asyncio implemented in C, i've got what is
for me a strange behavior of the asyncio.Task.current task
function. Executing the following test:

 import asyncio

 async def coro():
     print(asyncio.Task.current_task())
     print(asyncio.Task.current_task(None))
     print(asyncio.Task.current_task(loop=asyncio.get_event_loop()))

 loop = asyncio.get_event_loop()
 loop.run_until_complete(coro())

in Py3.5, I obtain the result:

<Task pending coro=<coro() running at test_task.py:4> cb=[_run_until_complete_cb() at /usr/lib/python3.5/asyncio/base_events.py:176]>
<Task pending coro=<coro() running at test_task.py:5> cb=[_run_until_complete_cb() at /usr/lib/python3.5/asyncio/base_events.py:176]>
<Task pending coro=<coro() running at test_task.py:6> cb=[_run_until_complete_cb() at /usr/lib/python3.5/asyncio/base_events.py:176]>

In Py3.6, i get:

<Task pending coro=<coro() running at test_task.py:4> cb=[_run_until_complete_cb() at /usr/lib/python3.6/asyncio/base_events.py:176]>
None
<Task pending coro=<coro() running at test_task.py:6> cb=[_run_until_complete_cb() at /usr/lib/python3.6/asyncio/base_events.py:176]>

What's going on here? It's still right to expect the same result from the three calls or something has changed?
The documentation for the Task.current_task() function seems unchanged between the two version.

My python3.6 has version:

$ python3.6 -VV
Python 3.6.0 (default, Dec 29 2016, 04:29:02) 
[GCC 6.2.1 20161215]

----------
assignee: yselivanov
components: asyncio
messages: 285445
nosy: gvanrossum, yselivanov
priority: normal
severity: normal
stage: patch review
status: open
title: Task.current_task(None) returns unexpected result
type: behavior
versions: Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29271>
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