Prevent premature closing of scoped event loops #714
Merged
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Fixes a bug that caused event loops to be closed prematurely when using async generator fixtures with class scope or wider in a function-scoped test.
The fixture setup of the "event_loop" fixture closes any existing loop. The existing loop could also belong to a pytest-asyncio scoped event loop fixture. This caused async generator fixtures using the scoped loop to raise a RuntimeError on teardown, because the scoped loop was closed before the fixture finalizer could not be run. In fact, everything after the async generation fixture's "yield" statement had no functioning event loop.
The issue was addressed by adding a special attribute to the scoped event loops provided by pytest-asyncio. If this attribute is present, the setup code of the "event_loop" fixture will not close the loop. This allows keeping backwards compatibility for code that doesn't use scoped loops. It is assumed that the magic attribute can be removed after the deprecation period of event_loop_ fixture overrides.
Fixes #708