Perform in check against cached fixturedefs (#404)

_preprocess_async_fixtures previously checked whether a fixturedef was identical to the fixture cache. This can never be the case. The intent of the if-clause was likely to prevent duplicate evaluation of fixtures.

This patch changes the if-statement to check whether the fixturedef is contained in the cache.

Author: DanCardin

CHANGELOG.rst

@@ -2,6 +2,10 @@
 Changelog
 =========
 
+UNRELEASED
+=================
+- Fixed an issue which prevented fixture setup from being cached. `#404 <https://github.com/pytest-dev/pytest-asyncio/pull/404>`_
+
 0.19.0 (22-07-13)
 =================
 - BREAKING: The default ``asyncio_mode`` is now *strict*. `#293 <https://github.com/pytest-dev/pytest-asyncio/issues/293>`_

pytest_asyncio/plugin.py

@@ -203,7 +203,7 @@ def _preprocess_async_fixtures(config: Config, holder: Set[FixtureDef]) -> None:
     fixturemanager = config.pluginmanager.get_plugin("funcmanage")
     for fixtures in fixturemanager._arg2fixturedefs.values():
         for fixturedef in fixtures:
-            if fixturedef is holder:
+            if fixturedef in holder:
                 continue
             func = fixturedef.func
             if not _is_coroutine_or_asyncgen(func):