Replace mark.async_timeout with fixtures

[delfick]

Fix #19

The pytest library is deprecating the ability to set marks on fixtures, which breaks how alt-pytest-asyncio currently determines async timeouts.

This change rewrites how all of that works to simplify and to make it so that fixtures and tests modify that timeout by requesting an async_timeout fixture which provides a set_timeout_seconds method for setting the timeout for that fixture/test.

Also this provides the ability to set defaults viadefault_async_timeout fixtures.

With a slight complication that the default is looked up in order via

• default_async_timeout
• class_default_async_timeout
• module_default_async_timeout
• package_default_async_timeout
• session_default_async_timeout

With the start point depending on the scope of the fixture. So a test will always start from the beginning of the order, but a "scope=module" fixture would start from module_default_async_timeout because a module scope fixture can't access class or function level fixtures, etc.

At the same time, I'm making it so that enabling the plugin requires adding alt_pytest_asyncio.enable to the pytest plugin list (this is a different tradeoff to one I was already making to cater for the ability to create the AltPytestAsyncioPlugin with a managed loop)

And I've changed the exported api of the plugin a little as mentioned in the README.

[brianmedigate]

@delfick Just because we can't mark fixtures doesn't mean we can't continue marking tests. Any reason you didn't leave the mark API for test functions and add the new fixture API for setting the timeout for a fixture? It seems like an unnecessarily breaking change, and it's a less elegant API (in my opinion).

[delfick]

@brianmedigate How much are you changing tests to have their own unique timeout?

[brianmedigate]

Not a ton, but we have a few tests which are slower than the default, so they currently have marks with longer timeouts, and I find it cleaner and easier to understand at a glance when it's done declaratively with a mark on the test rather than programatically inside the test function.

[delfick]

@brianmedigate yeah, I got rid of the marks altogether cause from my perspective the consistency is more important and less confusing and it should be pretty special case to change it per test, and for a group of tests it's possible to create a default_async_timeout fixture for that scope.

@pytest.fixture()
def default_async_timeout() -> float:
    return 0.5

[brianmedigate]

ok, thank you!