def compute_public_path(source)
              source += ".#{extension}" if missing_extension?(source)
              unless source =~ ProtocolRegexp
                source = "/#{directory}/#{source}" unless source[0] == ?/
                source = prepend_relative_url_root(source)
                source = rewrite_asset_path(source)
              end
              source = prepend_asset_host(source)
              source
            end