[FEATURE] Use anyio, so that ASGI support works for both asyncio and Trio

[Zac-HD]

The support for directly testing ASGI apps is really nice, but at the moment it doesn't support Trio - so I can't use it 😢

Fortunately this is pretty easy to fix by using anyio, a compatibility layer which can be run against either asyncio or Trio backends; it's already widely used by e.g. httpx and starlette/fastapi. What that would look like:

schemathesis/src/schemathesis/_hypothesis.py

Lines 99 to 106 in 8c4fe09

	def make_async_test(test: Callable) -> Callable:
	def async_run(*args: Any, **kwargs: Any) -> None:
	loop = asyncio.get_event_loop()
	coro = test(*args, **kwargs)
	future = asyncio.ensure_future(coro, loop=loop)
	loop.run_until_complete(future)
	return async_run

 def make_async_test(test: Callable) -> Callable: 
     def async_run(*args: Any, **kwargs: Any) -> None:
        return anyio.run(partial(test, *args, **kwargs))
  
     return async_run 

I think the main effort here would actually be to test something on trio as well as asyncio, which shouldn't be too hard to parametrize.

[Stranger6667]

The current blocker is that aiohttp test client depends on its own loop (provided via a fixture) and using anyio.run(partial(test, *args, **kwargs)) breaks it :(

[Zac-HD]

IIRC aiohttp is asyncio-specific, so you might need to switch that out for httpx. pytest-anyio may also be helpful?

[Stranger6667]

In the next release, @pytest.mark.trio and other ways of enabling trio support from pytest-trio will work 🎉