Basic test coverage

core/modules/navigation/src/Hook/NavigationHooks.php

@@ -202,12 +202,6 @@ public function navigationMenuLinkTreeAlter(array &$tree): void {
       if ($plugin_id == 'help.main' || $plugin_id == 'system.admin_content') {
         unset($tree[$key]);
       }
-
-      // Remove child items of content menu, if any.
-      $parent = $item->link->getParent();
-      if ($parent == 'system.admin_content') {
-        unset($tree[$key]);
-      }
     }
   }
 

core/modules/navigation/tests/navigation_test/src/Hook/NavigationTestHooks.php

@@ -34,4 +34,24 @@ public function blockAlter(&$definitions): void {
     }
   }
 
+  /**
+   * Implements hook_navigation_menu_link_tree_alter().
+   */
+  #[Hook('navigation_menu_link_tree_alter')]
+  public function navigationMenuLinkTreeAlter(array &$tree): void {
+    foreach ($tree as $key => $item) {
+      // Skip elements where menu is not the 'admin' one.
+      $menu_name = $item->link->getMenuName();
+      // Removes all items from menu1.
+      if ($menu_name == 'menu1') {
+        unset($tree[$key]);
+      }
+
+      // Updates title for items in menu2
+      if ($menu_name == 'menu2') {
+        $item->link->updateLink(['title' => 'New Link Title'], FALSE);
+      }
+    }
+  }
+
 }

core/modules/navigation/tests/src/Kernel/NavigationMenuLinkTreeTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\navigation\Kernel;
+
+use Drupal\Core\Menu\MenuTreeParameters;
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\navigation\Menu\NavigationMenuLinkTree;
+
+/**
+ * Tests \Drupal\navigation\Menu\NavigationMenuLinkTree.
+ *
+ * @group navigation
+ *
+ * @see \Drupal\navigation\Menu\NavigationMenuLinkTree
+ */
+class NavigationMenuLinkTreeTest extends KernelTestBase {
+
+  /**
+   * The tested navigation menu link tree.
+   *
+   * @var \Drupal\navigation\Menu\NavigationMenuLinkTree
+   */
+  protected NavigationMenuLinkTree $linkTree;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'field',
+    'layout_builder',
+    'layout_discovery',
+    'link',
+    'menu_link_content',
+    'menu_test',
+    'navigation',
+    'navigation_test',
+    'system',
+    'user',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('menu_link_content');
+
+    $this->linkTree = $this->container->get('navigation.menu_tree');
+  }
+
+  /**
+   * Tests the hook_navigation_menu_link_tree_alter logic.
+   */
+  public function testNavigationMenuLinkTreeAlter(): void {
+    /** @var \Drupal\system\MenuStorage $storage */
+    $storage = \Drupal::entityTypeManager()->getStorage('menu');
+    $storage->create(['id' => 'menu1', 'label' => 'Menu 1'])->save();
+    $storage->create(['id' => 'menu2', 'label' => 'Menu 2'])->save();
+
+    \Drupal::entityTypeManager()->getStorage('menu_link_content')->create(['link' => ['uri' => 'internal:/menu_name_test'], 'menu_name' => 'menu1', 'bundle' => 'menu_link_content', 'title' => 'Link test'])->save();
+    \Drupal::entityTypeManager()->getStorage('menu_link_content')->create(['link' => ['uri' => 'internal:/menu_name_test'], 'menu_name' => 'menu1', 'bundle' => 'menu_link_content', 'title' => 'Link test'])->save();
+    \Drupal::entityTypeManager()->getStorage('menu_link_content')->create(['link' => ['uri' => 'internal:/menu_name_test'], 'menu_name' => 'menu2', 'bundle' => 'menu_link_content', 'title' => 'Link test'])->save();
+
+    $output = $this->linkTree->load('menu1', new MenuTreeParameters());
+    $this->assertCount(2, $output);
+    $output = $this->linkTree->transform($output, []);
+    $this->assertCount(0, $output);
+    $output = $this->linkTree->load('menu2', new MenuTreeParameters());
+    $this->assertCount(1, $output);
+    $output = $this->linkTree->transform($output, []);
+    $this->assertCount(1, $output);
+    $item = reset($output);
+    $this->assertSame('New Link Title', $item->link->getTitle());
+  }
+
+}