If something ain’t broke don’t fix it. It’s an easy fix if you know which wire is which and you can return it to its original state

What’s most likely happened is the electrician pulled power from a device to the light and pulled a wire down to the switch. The black wire going to the white wire is bringing permanent power down to the switch to be controlled on the black wire up to the light while the white wire they had from the permanent power brought to the light box will be the neutral for the light. So you need to figure out which wire has power all the time and bring that to white of the opposite wire so that it can be switched again