I've spent a good hour debugging why the .svg file from my swipebox gem wasn't being precompiled by the Rails Asset Pipeline. I'm still not sure why, because it works with .svg fonts but for some reason it didn't want to "grab" the swipebox-icons.svg file.
The way I solved is I added an initializer to my Engine class which adds all the images (just in case) to the
module Swipebox class Engine < ::Rails::Engine initializer 'swipebox.assets.precompile' do |app| app.config.assets.precompile << %r(swipebox-[\w]+\.(?:png|svg|gif)$) end end end
Hope it helps someone :)