Ruby on Rails Less source maps and the asset pipeline?
In my opinion, the most convenient way to solve the problem: to abandon the assets pipeline and less-rails. change to gulp or blendid with gulp-less+gulp-less-sourcemap. This will take time to configure, but as my practice shows, the loss of time more than pays off with features like life edit, very fast compilation, and of course - sourcemaps.
In fact, I personally did not use less in such a bundle, but the implementation of sass is very convenient. I think that with less it could be the same
You can use pry to debug in rails. So, whereever you are using your css in the haml or html you can write something like -binding.pry( if its haml). Pry is used for debugging ruby code but you can also use it in your haml(view) using -.
Hope this helps.