fix(aria/menu): use computed for menu item patterns, with trigger on visible

Author: adolgachev

src/aria/menu/menu.ts

@@ -119,13 +119,15 @@ export class Menu<V> {
   readonly _pattern: MenuPattern<V>;
 
   /**
-   * The menu items as a writable signal.
-   *
-   * TODO(wagnermaciel): This would normally be a computed, but using a computed causes a bug where
-   * sometimes the items array is empty. The bug can be reproduced by switching this to use a
-   * computed and then quickly opening and closing menus in the dev app.
+   * The menu item patterns for the menu items that are direct children of this menu, passed
+   * to the menu pattern.
    */
-  private readonly _itemPatterns = () => this._items().map(i => i._pattern);
+  private readonly _itemPatterns = computed(() => {
+    // Needed to properly trigger recompute without contentChildren returning partial list.
+    this._pattern.visible();
+
+    return this._items().map(i => i._pattern);
+  });
 
   /** Whether the menu is visible. */
   readonly visible = computed(() => this._pattern.visible());