Summary

Hello everyone,

When attempting to create a new collection when it already exists, an IllegalStateException is thrown, in addition to the usual MongoCommandException.

This is a bug since the sync driver only throws the MongoCommandException, and this problem appears with the reactive streams driver since version 4.7.0 only.

How to Reproduce

MongoClient mongoClient = MongoClients.create();
MongoDatabase exampleDatabase = mongoClient.getDatabase("foo");

SubscriberHelpers.ObservableSubscriber<Void> voidSubscriber = new SubscriberHelpers.OperationSubscriber<>();
exampleDatabase.createCollection("bar").subscribe(voidSubscriber);
voidSubscriber.await(); 

If the collection already exists, you should see this stack trace: https://gist.github.com/Romitou/f552416d07f9608e2ddbecfa5c03e309

Additional Background

As said before, this bug only appears from version 4.7.0 and only on the reactive streams driver, I think this is relevant information.