conditionally prevent tree node selection

[zachsteffens]

I've got a p-tree that displays details when a tree node is selected. If any of those details are changed, I'd need to the user to save before they can navigate to a different node in the tree or away from the page entirely. I am using an Angular CanDeactivate guard to show a confirmation dialog when the user tries to navigate to a different page, but I'm having trouble doing something similar when a tree node is selected.

my pseudo-code is essentially

onNodeSelect(){ 

  -> are there unsaved changes?
      |-> (yes)
      |       -pause selection
      |       -show dialog
      |          ---> does the user want to abandon changes (wait for dialog response)
      |                  ---> (yes)
      |                            proceed with node selection
      |                  ---> (no)
      |                            abandon node selection
      |-> (no)
              proceed with node selection
}

But as far as I can tell, there is no way to intercept the nodeSelected event to inject this sort of code so I can stop the event propagation.
Am I missing something obvious?

I could use the "selectable" property on the nodes to prevent navigation, but users will have very limited context clues as to why they cant select a different node. I'd like to keep the UX for leaving the page and selecting a different node as similar as possible.