automatically reconnect pubsub when reading messages in blocking mode (#2281)

* optimistic default info on test sessionstart.
Makes test discovery work, even without a redis connection.

* Add unittests verifying that (non-async) PubSub will automatically reconnect

* Add tests for asyncio pubsub subsciription auto-reconnect

* automatically connect for blocking reads (asyncio)

* fix automatic connect on blocking pubsub read (non-async)

* lint & format

* Perform `connect()` call in PubSub code rather than `read_response`.

1 files changed, 9 insertions, 3 deletions

diff --git a/redis/asyncio/client.py b/redis/asyncio/client.py
index 3d59016..9c8caae 100644
--- a/redis/asyncio/client.py
+++ b/redis/asyncio/client.py
@@ -754,9 +754,15 @@ class PubSub:
 
         await self.check_health()
 
-        if not block and not await self._execute(conn, conn.can_read, timeout=timeout):
-            return None
-        response = await self._execute(conn, conn.read_response)
+        async def try_read():
+            if not block:
+                if not await conn.can_read(timeout=timeout):
+                    return None
+            else:
+                await conn.connect()
+            return await conn.read_response()
+
+        response = await self._execute(conn, try_read)
 
         if conn.health_check_interval and response == self.health_check_response:
             # ignore the health check message as user might not expect it