#84586 introduced some checks which execute npm list 4 times. They run unconditionally when executing ./x.py test ..., even if it is just to run tidy. On my system the added wall time exceeds that of running tidy itself.

I'll look into whether the checks themselves can be made be less wasteful. But if there are suggestions how to completely eliminate them or defer them while preserving their original purpose that would be great too.

CC @GuillaumeGomez can you explain the purpose of running this in should_run rather than erroring in run?