Issue #3411384 by phthlaap, venkatadapa, alecsmrekar, plach, alexpott, heddn,...

Issue #3411384 by phthlaap, venkatadapa, alecsmrekar, plach, alexpott, heddn, Graber: Error: Call to a member function label() on null in Drupal\menu_link_content\Form\MenuLinkContentForm->form() (line 99 of /var/www/html/docroot/core/modules/menu_link_content/src/Form/MenuLinkContentForm.php)

core/modules/menu_link_content/src/Form/MenuLinkContentForm.php

@@ -11,6 +11,7 @@
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\Core\Menu\MenuParentFormSelectorInterface;
 use Drupal\Core\Path\PathValidatorInterface;
+use Drupal\system\MenuInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -92,9 +93,9 @@ public function form(array $form, FormStateInterface $form_state) {
     $parent_id = $this->entity->getParentId() ?: $this->getRequest()->query->get('parent');
     $default = $this->entity->getMenuName() . ':' . $parent_id;
     $id = $this->entity->isNew() ? '' : $this->entity->getPluginId();
-    if ($this->entity->isNew()) {
-      $menu_id = $this->entity->getMenuName();
-      $menu = $this->entityTypeManager->getStorage('menu')->load($menu_id);
+    $menu_id = $this->entity->getMenuName();
+    $menu = $this->entityTypeManager->getStorage('menu')->load($menu_id);
+    if ($menu instanceof MenuInterface && $this->entity->isNew()) {
       $form['menu_parent'] = $this->menuParentSelector->parentSelectElement($default, $id, [
         $menu_id => $menu->label(),
       ]);

core/modules/menu_link_content/tests/src/Kernel/MenuLinksTest.php

@@ -459,4 +459,20 @@ public function testMenuLinkContentGetEntity(): void {
     $this->assertEquals($menu_link->id(), $tree_element->link->getEntity()->id());
   }
 
+  /**
+   * Tests that the form doesn't break for links with arbitrary menu names.
+   */
+  public function testMenuLinkContentFormInvalidParentMenu(): void {
+    $menu_link = MenuLinkContent::create([
+      'title' => 'Menu link test',
+      'provider' => 'menu_link_content',
+      'menu_name' => 'non-existent',
+      'link' => ['uri' => 'internal:/user/login'],
+    ]);
+    // Get the form for a new link, assert that building it doesn't break if
+    // the links menu name doesn't exist.
+    $build = \Drupal::service('entity.form_builder')->getForm($menu_link);
+    static::assertIsArray($build);
+  }
+
 }