I created a custom module with a page controller that returns a Symfony response (Symfony\Component\HttpFoundation\Response). The thing is I don't want to render my custom theme in this controller, just the theme_base template in this module.

$build = array(
  'page' => array(
    '#theme' => 'theme_base',
    '#content' => $content,
    '#owner' => $owner,
    '#cache' => [
      'max-age' => 0,
    '#attached' => array(
      'library' => array(

$html = \Drupal::service('renderer')->renderRoot($build);
$response = new Response();

return $response;

I tried attaching the module library to $build, or including it directly in Twig template but this doesn't seem to work.

Any ideas why this is not working? Or is there maybe another way I could do this?


  • If you are displaying it in a page in drupal site itself then you don't need to use renderRoot(). The libraries will be attached since drupal renders the renderable array $build that you return. Apr 29, 2018 at 14:09
  • I don't want to display it in a page. I would like to have it completely separate, only with whatever I put in my #theme_base template.
    – ptinca
    Apr 29, 2018 at 14:16

1 Answer 1


After rendering of $build the attachments have bubbled up to $build['#attached'] and you can add them to a response, which implements AttachmentsInterface, for example an HtmlResponse:

$html = \Drupal::service('renderer')->renderRoot($build);
$response = new HtmlResponse();
return $response;

To place the libraries on the page you have to enclose the page in an html render element

$build = [
  '#type' => 'html',
  'page' => [
     // content with attached libraries  

or implement the placeholders where the attachment will end up in a custom template, see template_preprocess_html().

  • I tried this, but now I get an error and still no attachments: "The website encountered an unexpected error. Please try again later. AssertionError: assert(is_string($chunk) || $chunk instanceof HtmlResponse) in assert() (line 259 of core/modules/big_pipe/src/Render/BigPipe.php). assert(, 'assert(is_string($chunk) || $chunk instanceof HtmlResponse)') (Line: 259)"
    – ptinca
    Apr 29, 2018 at 14:45
  • The error was my mistake, sorry. Disregard the above comment. But I'm still not getting attachments.
    – ptinca
    Apr 29, 2018 at 14:49
  • I think you need to enclose the page in an html render element to attach libraries: $build = ['#type' => 'html', 'page' => [... ]];
    – 4uk4
    Apr 29, 2018 at 16:23
  • This is it, thank you! Can you update you answer so I can accept it?
    – ptinca
    Apr 29, 2018 at 17:09

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