Add a feature to auto-load theme libraries.

Author: unclegcb

README.md

@@ -3,3 +3,15 @@ Extremely simple module to load a styleguide page.
 
 All opinions about the styleguide are part of the twig template in 
 the theme, which distinguishes it from other styleguide drupal modules.
+
+## Adding custom CSS/JS to the styleguide
+If you create a library in your theme (THEMENAME.library.yml) called
+`ts_styleguide`, it will be automatically loaded on your styleguide page.
+
+Example:
+```yaml
+ts_styleguide:
+  css:
+    theme:
+      assets/css/styleguide.css: {}
+```

src/Controller/StyleGuideController.php

@@ -4,37 +4,35 @@
 
 use Drupal\Core\Access\AccessResult;
 use Drupal\Core\Controller\ControllerBase;
-use Drupal\Component\Utility\Xss;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Twig\Error\LoaderError;
 
 /**
  * Creates style guide at /styleguide.
  */
 class StyleGuideController extends ControllerBase {
 
   /**
-   * The theme manager.
+   * The Library discovery service.
    *
-   * @var \Drupal\Core\Theme\ThemeManagerInterface
+   * @var \Drupal\Core\Asset\LibraryDiscoveryCollector
    */
-  protected $themeManager;
+  protected $libraries;
 
   /**
-   * The twig service.
+   * The theme manager.
    *
-   * @var \Drupal\Core\Template\TwigEnvironment
+   * @var \Drupal\Core\Theme\ThemeManagerInterface
    */
-  protected $twig;
+  protected $themeManager;
 
   /**
    * {@inheritDoc}
    */
   public static function create(ContainerInterface $container) {
     $instance = parent::create($container);
     $instance->configFactory = $container->get('config.factory');
+    $instance->libraries = $container->get('library.discovery');
     $instance->themeManager = $container->get('theme.manager');
-    $instance->twig = $container->get('twig');
     return $instance;
   }
 
@@ -46,11 +44,14 @@ public static function create(ContainerInterface $container) {
    */
   public function tsStyleGuide() {
     $themename = $this->configFactory->get('system.theme')->get('default');
-
-    return [
+    $content = [
       '#theme' => 'styleguide',
       '#theme_name' => $themename,
     ];
+    if ($this->libraries->getLibraryByName($themename, 'ts_styleguide')) {
+      $content['#attached']['library'][] = "$themename/ts_styleguide";
+    }
+    return $content;
   }
 
   /**