"Because above hack is done by replacing asyncio.get_event_loop and loop.create_task, therefore tasks and loops created by custom/private API won't behave correctly as expected, e.g. uvloop.new_event_loop() or asyncio.Task(). Also, event loops created before importing aiocontextvars are not patched either. So over all, you should import aiocontextvars at the beginning before creating event loops, and always use asyncio.* to operate loops/policies, and public asyncio API to create tasks."

Does this mean I can't use uvloop at all, or just don't use the uvloop.new_event_loop()?

PEP-567 is accepted for Python 3.7. We should make this library compatible. contextvars should replace this library.

contextvars==2.4 was released.

Hi, aiocontextvars locked the version constraint of contextvars as contextvars ==2.4, which leads a troubling scenario to its direct downstream project gumbelcodes which has dependency contextvars.

What makes the situation worse is that the downstream projects [gumbelcodes, flexget, pysoa] of aiocontextvars are also have dependency contextvars.

Could you please loosen the version constraint of contextvars?
Benefit of this is that users using both of aiocontextvars and contextvars can upgrade their third party libraries in a timely manner to reduce technical debts.

Solution

The dependency trees of your project and affected downstream projects are shown as follows.
Taking the version constraints of upstream and downstream projects into comprehensive consideration, you can

1. Loosen click to be contextvars >=2.4.

@pyup-bot May I submit a PR to this issue?

Thanks for your attention.
Best,
Neolith

It would be useful to at least have some minimal usage examples in the read me file. Of course, documentation would even be better.

• aiocontextvars version:
• Python version:3.6
• Operating System: Linux

Description

Describe what you were trying to get done.
Tell us what happened, what went wrong, and what you expected to happen.

What I Did

python setup.py install

when i execute python setup.py install,returned no results

• aiocontextvars version:0.2.2
• Python version: 3.6
• Operating System: macos

Description

Describe what you were trying to get done.
Tell us what happened, what went wrong, and what you expected to happen.

We are using encode/databases, which uses aiocontextvars.

The thread local state should be type checked. For now, the lookup will tend to return context if other library also sets a same named thread local variable.
So the name should be namespaced to provide less chances of error.

def _get_context():
    ctx = getattr(_state, 'context', None)
   # ctx may not be null, but of other type.
    if ctx is None:
        ctx = Context()
        _state.context = ctx
    return ctx

_state = threading.local()

What I Did

One of our library sets the context as dictionary.

  File "/Users/ramandeepsingh/.pyenv/versions/3.6.10/lib/python3.6/site-packages/contextvars/__init__.py", line 110, in set
    data = ctx._data
AttributeError: 'dict' object has no attribute '_data'

• aiocontextvars version: 0.2.2
• Python version: 3.5.0
• Operating System: Ubuntu 18.04.3

Description

Mismatching results when running an asyncio script with Python 3.5.0 and aiocontextvars vs. Python 3.7.5rc1 and native contextvars package.

What I Did

I created a virtual environment with Python 3.5.0 and installed aiocontextvars via pip3. I activated the virtual environment and ran the script below. I ran the same script with Python 3.7.5rc1 and got different results. The results that I got from running with Python 3.7.5rc1 are the ones I expected. When I run the script with aiocontextvars it seems like the ContextVar value is not kept independently for the different async functions that set its value.

(3-5-0) ocelotl@harrison:~$ cat async_contextvar.py 
from asyncio import sleep, gather, get_event_loop
from contextvars import ContextVar

local_name = ContextVar("async_name")


async def waiting(async_name, first_sleep, second_sleep):

    await sleep(first_sleep)

    local_name.set(async_name)

    print("async_name:\t{}".format(async_name))
    print("local_name:\t{}".format(local_name.get()))
    print()

    await sleep(second_sleep)

    print("async_name:\t{}".format(async_name))
    print("local_name:\t{}".format(local_name.get()))
    print()


async def main():
    await gather(waiting("A", 0, 1), waiting("B", 0.1, 3), waiting("C", 2, 1))

loop = get_event_loop()
loop.run_until_complete(main())
loop.close()

(3-5-0) ocelotl@harrison:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.3 LTS
Release:        18.04
Codename:       bionic
(3-5-0) ocelotl@harrison:~$ python3 --version
Python 3.5.0
(3-5-0) ocelotl@harrison:~$ pip3 freeze
aiocontextvars==0.2.2
contextvars==2.4
immutables==0.11
You are using pip version 7.1.2, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
(3-5-0) ocelotl@harrison:~$ python3 async_contextvar.py 
async_name:     A
local_name:     A

async_name:     B
local_name:     B

async_name:     A
local_name:     B

async_name:     C
local_name:     C

async_name:     C
local_name:     C

async_name:     B
local_name:     C

(3-5-0) ocelotl@harrison:~$ 

ocelotl@harrison:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.3 LTS
Release:        18.04
Codename:       bionic
ocelotl@harrison:~$ python3 --version
Python 3.7.5rc1
ocelotl@harrison:~$ python3 async_contextvar.py 
async_name:     A
local_name:     A

async_name:     B
local_name:     B

async_name:     A
local_name:     A

async_name:     C
local_name:     C

async_name:     C
local_name:     C

async_name:     B
local_name:     B

ocelotl@harrison:~$ 

• aiocontextvars version: 0.2.0 (master @ b36af92)
• Python version: 3.6.6
• Operating System: macOS High Sierra (10.13.6)

Description

The patching process introduced by aiocontextvars is not correctly handling setting the event loop to None and raises an AttributeError. I discovered this while adding aiocontextvars to my project which also uses aiohttp and their test utilities. aiohttp's test utils set the event loop to None as part of test teardown (see here).

What I Did

Minimally reproducing code:

>>> import asyncio
>>> import aiocontextvars
>>> asyncio.set_event_loop(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/jdot/code/vendor/aiocontextvars/aiocontextvars/__init__.py", line 67, in set_event_loop
    return _set_event_loop(_patch_loop(loop))
  File "/Users/jdot/code/vendor/aiocontextvars/aiocontextvars/__init__.py", line 57, in _patch_loop
    loop._orig_create_task = loop.create_task
AttributeError: 'NoneType' object has no attribute 'create_task'

I believe this can be fixed with a one line change.

• aiocontextvars version: 0.2.2
• Python version: 3.5.2
• Ubuntu Xenial LTS

Original bug report: matrix-org/synapse#5199

Description

On Ubuntu Xenial supported Python 3.5 is 3.5.2.

On Python 3.5.2 asyncio doesn't have asyncio._get_running_loop.

Example traceback (copied from itamarst/eliot#418 (comment)):

Python 3.5.2 (default, Nov 23 2017, 16:37:01) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import eliot
>>> eliot.current_action()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/synapse/env3/lib/python3.5/site-packages/eliot/_action.py", line 53, in current_action
    return _ACTION_CONTEXT.get(None)
  File "/home/synapse/env3/lib/python3.5/site-packages/contextvars/__init__.py", line 94, in get
    ctx = _get_context()
  File "/home/synapse/env3/lib/python3.5/site-packages/aiocontextvars.py", line 19, in _get_context
    state = _get_state()
  File "/home/synapse/env3/lib/python3.5/site-packages/aiocontextvars.py", line 33, in _get_state
    loop = asyncio._get_running_loop()
AttributeError: module 'asyncio' has no attribute '_get_running_loop'

Solution

Haven't tried this yet, but:

if sys.version_info < (3, 5, 3):
    import asyncio
    from asyncio import events
    asyncio._get_running_loop = events._get_running_loop
    asyncio._set_running_loop = events._set_running_loop