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.

報告された失敗は、asyncpg/cluster.py の TempCluster.start() 周辺と、その _test_connection(timeout=wait) の呼び出しにあります。pytest または独自のイベントループを持つ別の環境で開始パスを再現し、その後、要求されたループ引数がそのパスを通じてどのように渡されるべきかを判断してください。cluster.start() が nest_asyncio を必要とせずに呼び出し元のイベントループを使用でき、報告されたシナリオのカバレッジがあることが完了の条件です。