fix(connection): disable createConnection buffering if autoCreate option is changed

[lpizzinidev]

fix #12940

Summary
Avoid usage of cached createCollection callback if autoCreate option value has changed.

[lpizzinidev]

@vkarpov15
Do you think that this is the correct approach?
If so I'll setup a MongoDB 4.0.x env to check why tests are failing on that specific version only.
Otherwise I'll search for another way to solve the issue.

[vkarpov15]

The problem with this approach is that you may have multiple $init's going at the same time. Model.init(); Model.schema.options.autoCreate = false; Model.init();. The purpose of $init is to avoid that.

I think a better approach would be to move the utils.getOption() call for autoCreate into the _createCollection() function itself. And put _createCollection() behind buffering like how _wrapConnHelper() works.

[lpizzinidev]

Thanks for the feedback 💪 I'll work on this

[vkarpov15]

For consistency, let's also delay checking autoIndex until after buffering is done. Apply similar changes to _ensureIndexes(). No need to do _wrapCollHelper on _ensureIndexes() though, since _createCollection() will already wait for buffering.

[vkarpov15]

Also, let's not add a separate _wrapCollHelper() function, since that function won't be reused anywhere. Just add the if ((conn.readyState === STATES.connecting || conn.readyState === STATES.disconnected) && conn._shouldBufferCommands()) check directly into _createCollection().

[vkarpov15]

Thanks 👍