`prompt_async` is blocking on windows

[eric-wieser]

Consider the following:

import asyncio

from prompt_toolkit.shortcuts import prompt_async

async def spam():
    while True:
        print("hello");
        await asyncio.sleep(0.1);
        print("World");
        await asyncio.sleep(0.1);


async def my_coroutine():
    while True:
        result = await prompt_async('Say something: ', patch_stdout=True)
        print('You said: %s' % result)

loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(my_coroutine(), spam()))
loop.close()

What I expect to happen: The prompt is pushed down by a continual stream of Hello and World

What actually happens: Each time I push a single character, an extra Hello or World is printed - the output does not advance while waiting for a single character.

[jonathanslenders]

Hi @eric-wieser,

Thank you for reporting! I think this is a windows-only issue. The way that stdin is read blocks the event loop. If I recall correctly, this was fixed on the 2.0 branch. Could you check that out? I believe that the code above is compatible with 2.0. (However, it'll still take some time for 2.0 to release.)

Thanks,
Jonathan

[eric-wieser]

Running this in the 2.0 branch:

$ pip3 install --user -U git+https://github.com/jonathanslenders/python-prompt-toolkit@2.0
Collecting git+https://github.com/jonathanslenders/python-prompt-toolkit@2.0
  Cloning https://github.com/jonathanslenders/python-prompt-toolkit (to 2.0) to c:\users\wiese\appdata\local\temp\pip-df62834i-build
Requirement already up-to-date: six>=1.9.0 in c:\users\wiese\appdata\roaming\python\python35\site-packages (from prompt-toolkit==1.0.9)
Requirement already up-to-date: wcwidth in c:\users\wiese\appdata\roaming\python\python35\site-packages (from prompt-toolkit==1.0.9)
Installing collected packages: prompt-toolkit
  Found existing installation: prompt-toolkit 1.0.14
    Uninstalling prompt-toolkit-1.0.14:
      Successfully uninstalled prompt-toolkit-1.0.14
  Running setup.py install for prompt-toolkit ... done
Successfully installed prompt-toolkit-1.0.9

Gives the following error:

Traceback (most recent call last):
  File "main.py", line 20, in <module>
    loop.run_until_complete(asyncio.gather(my_coroutine(), spam()))
  File "C:\Program Files\Python 3.5\lib\asyncio\base_events.py", line 342, in run_until_complete
    return future.result()
  File "C:\Program Files\Python 3.5\lib\asyncio\futures.py", line 274, in result
    raise self._exception
  File "C:\Program Files\Python 3.5\lib\asyncio\tasks.py", line 239, in _step
    result = coro.send(value)
  File "main.py", line 16, in my_coroutine
    result = await prompt_async('Say something: ')
  File "<string>", line 6, in prompt_async
NameError: name 'create_asyncio_event_loop' is not defined

The offending line is here

Also, can you update the version number in the 2.0 branch to actually look like version 2? It's pretty alarming right now that instaling 2 takes me back to version 1.0.9.

Relatedly: are the commits from 1.0.9 - 1.0.14 backported to 2.0?

[eric-wieser]

eventloop.utils.AsyncioTimeout is also missing, even though 'AsyncioTimeout' in eventloop.utils.__all__.

Are there no automated tests on the 2.0 branch to catch these things?

[jonathanslenders]

Hi @eric-wieser,
Can you check whether this is still the case with the 2.0.1 release?
If not, I can close this issue.
Thanks!

[BYK]

Tested this with the modernized version of the initial case:

import asyncio
from prompt_toolkit import PromptSession
from prompt_toolkit.patch_stdout import patch_stdout

async def spam():
    while True:
        print("hello");
        await asyncio.sleep(0.1);
        print("World");
        await asyncio.sleep(0.1);


async def my_coroutine():
    session = PromptSession()
    while True:
        with patch_stdout():
            result = await session.prompt_async('Say something: ')
        print('You said: %s' % result)


loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.gather(my_coroutine(), spam()))
loop.close()

Seems to be working as expected (prompt line is continuously pushed down even when typing).