检测协程是否需要异步循环

Question

I'm writing code that will wait on user-supplied coroutines using Twisted. In a simpler case all I need is to use defer.ensureDeferred to turn a coroutine into a Deferred. But if a coroutine uses eg asyncio.sleep() I need to use asyncio.ensure_future to wrap it into an asyncio Task that will run in the asyncio loop and this needs AsyncioSelectorReactor . I want to support the first case even if AsyncioSelectorReactor is not used and so I don't want to call asyncio.ensure_future on all coroutines. The only way to do this that I can think of is somehow detecting if the coroutine needs asyncio, is that possible to do? Or, maybe, there is a simpler way to do this?

Answer 1

It might help to check if asyncio is referenced inside the coroutine. Consider these examples:

import asyncio

async def test1():
    pass

async def test2():
    await asyncio.sleep(10)

del asyncio
async def test3():
    import asyncio

Using inspect.getclosurevars , you can check for the presence of asyncio:

assert 'asyncio' not in inspect.getclosurevars(test1).globals or inspect.getclosurevars(test2).globals

assert 'asyncio' in inspect.getclosurevars(test2).globals

assert 'asyncio' in inspect.getclosurevars(test3).unbound

Of course, this is would give a false positive when the user's coroutine imports something from asyncio that doesn't use the loop, such as exceptions or constants, or when the user code doesn't use the imported coroutines.