big_pipe_page_attachments

big_pipe_page_attachments(array &$page)

function big_pipe_page_attachments(array &$page) {
  // Routes that don't use BigPipe also don't need no-JS detection.
  if (\Drupal::routeMatch()->getRouteObject()->getOption('_no_big_pipe')) {
    return;
  }

  $request = \Drupal::request();
  // BigPipe is only used when there is an actual session, so only add the no-JS
  // detection when there actually is a session.
  // @see \Drupal\big_pipe\Render\Placeholder\BigPipeStrategy.
  $session_exists = \Drupal::service('session_configuration')->hasSession($request);
  $page['#cache']['contexts'][] = 'session.exists';
  // Only do the no-JS detection while we don't know if there's no JS support:
  // avoid endless redirect loops.
  $has_big_pipe_nojs_cookie = $request->cookies->has(BigPipeStrategy::NOJS_COOKIE);
  $page['#cache']['contexts'][] = 'cookies:' . BigPipeStrategy::NOJS_COOKIE;
  if ($session_exists) {
    if (!$has_big_pipe_nojs_cookie) {
      // Let server set the BigPipe no-JS cookie.
      $page['#attached']['html_head'][] = [
        [
          // Redirect through a 'Refresh' meta tag if JavaScript is disabled.
          '#tag' => 'meta',
          '#noscript' => TRUE,
          '#attributes' => [
            'http-equiv' => 'Refresh',
            // @todo: Switch to Url::fromRoute() once https://www.drupal.org/node/2589967 is resolved.
            'content' => '0; URL=' . Url::fromUri('internal:/big_pipe/no-js', ['query' => \Drupal::service('redirect.destination')->getAsArray()])->toString(),
          ],
        ],
        'big_pipe_detect_nojs',
      ];
    }
    else {
      // Let client delete the BigPipe no-JS cookie.
      $page['#attached']['html_head'][] = [
        [
          '#tag' => 'script',
          '#value' => 'document.cookie = "' . BigPipeStrategy::NOJS_COOKIE . '=1; path=/; expires=Thu, 01 Jan 1970 00:00:00 GMT"',
        ],
        'big_pipe_detect_js',
      ];
    }
  }
}