get_categories() and related functions, by default, don't return empty categories - categories with no posts.
I thought that, since there may be some underlying code checking the post counts, is it possible to additionally filter that list to only include categories that themselves contain posts that have a certain, specific Tag associated?
Or is there a somewhat simple alternate method of getting that information?
For example, if I had some posts with a Tag of "audio", I'd like a way to use
get_categories() (or similar results) but only retrieve a list of categories that contained posts with that "audio" Tag.
I am aware that I may have to use the Tag ID directly. I'm just looking for the "best", or most appropriate way to do this.