Ability to trigger check event during expand event

I have a dynamically-loading tree that doesn't load children until the parent is expanded. The fetch mechanism doesn't have enough information to tell the UI whether the node is an unexpanded intermediate node or a leaf node. Therefore in the UI I display both as an expandable node and update it after it is expanded.

This works well, with the exception of having to interact with leaf node twice to check it (once to expand it and realize it's not expandable, and second time to check the box). I would like to do this in one step, expand the node and if it's a leaf node then automatically check it as it's loaded. The problem is that I don't see a mechanism for triggering a check programmatically from within onExpand method.

Start by reviewing the tree component's onExpand handling and the existing expand and check event behavior. The change is done when expanding a dynamically loaded leaf can trigger its check action in the same interaction, without requiring a second user action.