Pytest does not notify users when async tests are ignored

[LukeWood]

What's the problem this feature will solve?

When writing async unit-tests, it is extremely easy to forget to install the pytest-async extension and end up ignoring the futures.
This can cause unexpected silence:

async def test_should_fail_but_doesnt():
    assert False

This passes if pytest-async is not installed. Instead, I'd like to propose we make this fail with a nice message indicating that you need too install python-async.

Describe the solution you'd like

I'd like to inspect tests to see if they return a future. If they return a future, and pytest-async is not installed i'd like to error out and tell users to install it.

Alternative Solutions

Ignore the tests.

Additional context

I've been bit by this once~ know another team member of mine who has also been bitten by this.
I'm happy to contribute this.

[RonnyPfannschmidt]

More details needed,pytest notifies when async tests are there without a async plugin

[LukeWood]

More details needed,pytest notifies when async tests are there without a async plugin

Oh interesting! I had no idea- maybe I missed it in the logs?

what does notify mean in this context? Error or warning? If a warning maybe we should upgrade it to an error and gate the warning behind an environment variable?

[RonnyPfannschmidt]

Warnings

[LukeWood]

Thanks Maybe we should consider upgrading the default and allow opt out via a config variable?

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[RonnyPfannschmidt]

@nicoddemus @asottile @bluetech

I'm +1 on turning those into a failure for 8.x and would like your input

[Zac-HD]

Sounds good to me - we could even recommend a particular plugin based on sys.modules:

if pkgs := " or ".join(
    f"pytest-{n}" for n in ("anyio", "asyncio", "trio) 
    if n in sys.modules and f"pytest_{n}" not in sys.modules
):
    error_msg += "  Consider installing {pkgs}."

[Zac-HD]

Relevant code is here. We should convert from a warning to an error, and include the nodeid in the error message - it's not currently included in this warning!

It'd also be good to turn other non-None returns into an error; that's similarly a few years past when we planned to finish the transition.