Making some experiment I've found that getJSON is called only with the the last CSS imported file.

I created a CSS file with two included files, e.g.

@import './styles/first.css'
@import './styles/second.css'

And then I found that getJSON is only called with the mapped names corresponding to second.css. I tried only with the first import (first.css) and I got the mapping for it, but when I added the second.css then I got the mapping for the second.css meanwhile I expected to find all of them.

I also realised that filename received as first parameter in getJSON is always undefined at least for this specific scenario.