Awaiting on WebSocketResponse.send_* does not work

[mind1m]

Long story short

In documentation it says:

New in version 1.3.0.
To enable back-pressure from slow websocket clients treat methods ping(), pong(), send_str(), send_bytes(), send_json() as coroutines. By default write buffer size is set to 64k.

http://aiohttp.readthedocs.io/en/stable/web_reference.html?highlight=back%20pressure#websocketresponse

However, if I try to do it, I get:

Error handling request
Traceback (most recent call last):
  File ".../env/lib/python3.6/site-packages/aiohttp/web_server.py", line 62, in handle_request
    resp = yield from self._handler(request)
  File ".../env/lib/python3.6/site-packages/aiohttp/web.py", line 270, in _handle
    resp = yield from handler(request)
  File "ws_srv.py", line 8, in wshandler
    await ws.send_str('hello')
TypeError: object tuple can't be used in 'await' expression

It can be seen, that when writer's buffer is not full, WebSocketWriter._send_frame returns a tuple https://github.com/KeepSafe/aiohttp/blob/e49b59b0594ca4c21a3f788ffcbe0005c79daa65/aiohttp/_ws_impl.py#L457 . Maybe it should be async function or return a Future?

Expected behaviour

Awaiting on WebSocketResponse.send_* should work.

Actual behaviour

Awaiting on WebSocketResponse.send_* when buffer is not full results in TypeError: object tuple can't be used in 'await' expression.

Steps to reproduce

ws_server.py

import asyncio
from aiohttp.web import Application, WebSocketResponse, run_app


async def wshandler(request):
    ws = WebSocketResponse()
    await ws.prepare(request)
    await ws.send_str('hello')
    await ws.close()
    print('Processed client')
    return ws

async def init(loop):
    app = Application(loop=loop)
    app.router.add_get('/', wshandler)
    return app

loop = asyncio.get_event_loop()
app = loop.run_until_complete(init(loop))
run_app(app)

ws_client.py

import asyncio
import aiohttp


async def f():
    session = aiohttp.ClientSession()
    async with session.ws_connect('http://localhost:8080') as ws:
        answer = await ws.receive_str()
        assert answer == 'hello'
        print('Got correct answer, exiting..')
    await session.close()

asyncio.get_event_loop().run_until_complete(f())

Your environment

aiohttp 1.3.1, Python 3.6, OS 10.12.2

[mind1m]

I can prepare PR, if someone advises me on how to fix the issue.

[kxepal]

But all websocket write methods are not awaitable since the start. Why to make them awaitable?

[kxepal]

Hm...I guess, documentation need to clarify the moment with "coroutines". /cc @fafhrd91

[fafhrd91]

Technically they are not coroutines but they return coroutine object

[fafhrd91]

@mind1master we need to add empty coroutine and return it instead of ()

[fafhrd91]

fixed in 1.3 branch, i will release 1.3.2 later today

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