TempCluster() and pytest

• asyncpg version: 0.23.0
• PostgreSQL version: N/A
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: N/A
• Python version: 3.8.9 (but N/A)
• Platform: N/A
• Do you use pgbouncer?: N/A
• Did you install asyncpg with pip?: yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and
  uvloop?:

This is issue which happens when using TempCluster() for testing as mentioned in https://github.com/MagicStack/asyncpg/issues/589.

Basically invoking cluster.start() causes an error when trying to use in environment that sets up own event loop (like pytest). Because .start() calls self._test_connection(timeout=wait) which creates and uses own event loop (https://github.com/MagicStack/asyncpg/blob/d08a9b8b9c2c68d469aeb9c4112d83c56c24f11c/asyncpg/cluster.py#L467).

This can be worked around by using nest_asyncio package, but it would be great if we could pass the event loop to the start() method so no hacking around that would be needed.

L’échec signalé se situe dans asyncpg/cluster.py, autour de TempCluster.start() et de son appel à _test_connection(timeout=wait). Reproduisez le chemin de démarrage avec pytest ou dans un autre environnement disposant de sa propre boucle d’événements, puis déterminez comment l’argument de boucle demandé doit être transmis tout au long de ce chemin. Le travail est terminé lorsque cluster.start() peut utiliser la boucle d’événements de l’appelant sans nécessiter nest_asyncio, avec une couverture du scénario signalé.