PHP+MongoDB: "Return value must be of type MongoDB\Driver\Server, null returned" about mongo-php-library

[simillo01]

Sure Thank you, i'll try again with the 1.15 version of the driver and update you as soon as possible. Thank you for your help.

[alcaeus]

The select_server function is a helper providing additional functionality around the MongoDB\Driver\Manager::selectServer method relevant in the library. Its purpose is to select the correct server to handle a command according to the command type (i.e. read vs. write) and the specified read preference (primary, secondary, etc.). It also takes into account that the command options may include a session that has been pinned to a specific server. Looking at the call stack you provided, I can not find a code path that wouldn't return a MongoDB\Driver\Server instance without throwing an exception, so I'm a bit confused as to what's causing this.

If server selection fails, the driver throws an exception based on the error returned from server selection. In other cases, we always initialise the return value of MongoDB\Driver\Server::selectServer to a server instance. Technically there's no code path that would produce a null value with a type error in this method.

That said, the new 1.15 releases for the driver (PHP extension and library) improve typing significantly, both by leveraging return and parameter types, but also by integrating psalm for additional type checking. I'd appreciate it if you could update to the latest versions and see if the error persists. If so, I'll take another look to try and reproduce this. However, this may involve testing with the cluster you're connecting to, so let's try updating first to see if that already fixes the issue.

[jmikola]

Closing this due to inactivity. Feel free to follow up if the issue persists in 1.15 and we can re-open.