Add placeholder option to drupal_menu()

src/TwigTweakExtension.php

@@ -209,8 +209,8 @@ class TwigTweakExtension extends AbstractExtension {
   /**
    * Returns the render array for Drupal menu.
    */
-  public static function drupalMenu(string $menu_name, int $level = 1, int $depth = 0, bool $expand = FALSE): array {
-    return \Drupal::service('twig_tweak.menu_view_builder')->build($menu_name, $level, $depth, $expand);
+  public static function drupalMenu(string $menu_name, int $level = 1, int $depth = 0, bool $expand = FALSE, bool $placeholder = FALSE): array {
+    return \Drupal::service('twig_tweak.menu_view_builder')->build($menu_name, $level, $depth, $expand, $placeholder);
   }
 
   /**

src/View/MenuViewBuilder.php

@@ -2,12 +2,14 @@
 
 namespace Drupal\twig_tweak\View;
 
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Menu\MenuLinkTreeInterface;
+use Drupal\Core\Security\TrustedCallbackInterface;
 
 /**
  * Menu view builder.
  */
-class MenuViewBuilder {
+class MenuViewBuilder implements TrustedCallbackInterface {
 
   /**
    * The menu link tree service.
@@ -40,7 +42,35 @@ class MenuViewBuilder {
    *
    * @see \Drupal\system\Plugin\Block\SystemMenuBlock::build()
    */
-  public function build(string $menu_name, int $level = 1, int $depth = 0, bool $expand = FALSE): array {
+  public function build(string $menu_name, int $level = 1, int $depth = 0, bool $expand = FALSE, bool $placeholder = FALSE): array {
+    $cache = [
+      'keys' => [
+        'twig_tweak_menu',
+        $menu_name,
+        '[level]=' . $level,
+        '[depth]=' . $depth,
+        '[expand]=' . (int) $expand,
+      ],
+      'contexts' => [
+        'route.menu_active_trails:' . $menu_name,
+      ],
+      'tags' => [
+        'config:system.menu.' . $menu_name,
+      ]
+    ];
+
+    if ($placeholder) {
+      return [
+        'menu' => [
+          '#lazy_builder' => [
+            'twig_tweak.menu_view_builder:build',
+            [$menu_name, $level, $depth, $expand, FALSE],
+          ],
+          '#cache' => $cache,
+        ],
+      ];
+    }
+
     $parameters = $this->menuLinkTree->getCurrentRouteMenuTreeParameters($menu_name);
 
     // Adjust the menu tree parameters based on the block's configuration.
@@ -66,19 +96,17 @@ class MenuViewBuilder {
     $tree = $this->menuLinkTree->transform($tree, $manipulators);
     $build = $this->menuLinkTree->build($tree);
 
-    if (!isset($build['#cache']['keys'])) {
-      $build['#cache']['keys'] = [
-        'twig_tweak_menu',
-        $menu_name,
-        '[level]=' . $level,
-        '[depth]=' . $depth,
-        '[expand]=' . (int) $expand,
-      ];
-    }
-
-    $build['#cache']['contexts'][] = 'route.menu_active_trails:' . $menu_name;
+    $build['#cache']['keys'] = array_unique(array_merge($cache['keys'], $build['#cache']['keys'] ?? []));
+    $build['#cache']['contexts'] = Cache::mergeContexts($cache['contexts'], $build['#cache']['contexts'] ?? []);
+    $build['#cache']['tags'] = Cache::mergeTags($cache['tags'], $build['#cache']['tags'] ?? []);
 
     return $build;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function trustedCallbacks(): array {
+    return ['build'];
+  }
 }