Fast404ExceptionHtmlSubscriber::on404

public Fast404ExceptionHtmlSubscriber::on404(GetResponseForExceptionEvent $event)

public function on404(GetResponseForExceptionEvent $event) {
  $request = $event->getRequest();

  $config = $this->configFactory->get('system.performance');
  $exclude_paths = $config->get('fast_404.exclude_paths');
  if ($config->get('fast_404.enabled') && $exclude_paths && !preg_match($exclude_paths, $request->getPathInfo())) {
    $fast_paths = $config->get('fast_404.paths');
    if ($fast_paths && preg_match($fast_paths, $request->getPathInfo())) {
      $fast_404_html = strtr($config->get('fast_404.html'), ['@path' => Html::escape($request->getUri())]);
      $response = new Response($fast_404_html, Response::HTTP_NOT_FOUND);
      $event->setResponse($response);
    }
  }
}