class Middleman::SourceWatcher

def update(updated_paths, removed_paths)
  valid_updates = updated_paths
                  .map { |p| @files[p] || path_to_source_file(p, @directory, @type, @options[:destination_dir]) }
                  .select(&method(:valid?))
  valid_updates.each do |f|
    record_file_change(f)
    logger.debug "== Change (#{f[:types].inspect}): #{f[:relative_path]}"
  end
  related_sources = valid_updates.map { |u| u[:full_path] } + removed_paths
  related_updates = ::Middleman::Util.find_related_files(app, related_sources).select(&method(:valid?))
  related_updates.each do |f|
    logger.debug "== Possible Change (#{f[:types].inspect}): #{f[:relative_path]}"
  end
  valid_updates |= related_updates
  valid_removes = removed_paths
                  .select(&@files.method(:key?))
                  .map(&@files.method(:[]))
                  .select(&method(:valid?))
                  .each do |f|
                    remove_file_from_cache(f)
                    logger.debug "== Deletion (#{f[:types].inspect}): #{f[:relative_path]}"
                  end
  unless valid_updates.empty? && valid_removes.empty?
    execute_callbacks(:on_change, [
                        valid_updates,
                        valid_removes,
                        self
                      ])
  end
  [valid_updates, valid_removes]
end