# File lib/nanoc/extra/checking/checks/internal_links.rb, line 11
    def run
      # TODO de-duplicate this (duplicated in external links check)
      filenames = self.output_filenames.select { |f| File.extname(f) == '.html' }
      hrefs_with_filenames = ::Nanoc::Extra::LinkCollector.new(filenames, :internal).filenames_per_href
      hrefs_with_filenames.each_pair do |href, filenames|
        filenames.each do |filename|
          unless valid?(href, filename)
          self.add_issue(
            "reference to #{href}",
            :subject  => filename)
          end
        end
      end
    end