Issue #3379293 by benjifisher, lauriii, pooja saraah, smustgrave, poker10:...

Issue #3379293 by benjifisher, lauriii, pooja saraah, smustgrave, poker10: Make it easier to add a child menu item

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

@@ -89,7 +89,8 @@ public static function create(ContainerInterface $container) {
   public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
 
-    $default = $this->entity->getMenuName() . ':' . $this->entity->getParentId();
+    $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();

core/modules/menu_ui/src/MenuForm.php

@@ -3,6 +3,7 @@
 namespace Drupal\menu_ui;
 
 use Drupal\Component\Utility\NestedArray;
+use Drupal\Component\Utility\SortArray;
 use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Entity\EntityForm;
 use Drupal\Core\Form\FormStateInterface;
@@ -434,6 +435,21 @@ protected function buildOverviewTreeForm($tree, $delta) {
           '#default_value' => $link->getParent(),
         ];
         $operations = $link->getOperations();
+        if ($element->depth < $this->menuTree->maxDepth()) {
+          $add_link_url = Url::fromRoute(
+            'entity.menu.add_link_form',
+            ['menu' => $this->entity->id()],
+            ['query' => ['parent' => $link->getPluginId()]]
+          );
+          $operations += [
+            'add-child' => [
+              'title' => $this->t('Add child'),
+              'weight' => 20,
+              'url' => $add_link_url,
+            ],
+          ];
+          uasort($operations, [SortArray::class, 'sortByWeightElement']);
+        }
         foreach ($operations as $key => $operation) {
           if (!isset($operations[$key]['query'])) {
             // Bring the user back to the menu overview.

core/modules/menu_ui/tests/src/Functional/MenuUiTest.php

@@ -504,6 +504,10 @@ public function doMenuTests() {
     $this->toggleMenuLink($item1);
     $this->toggleMenuLink($item2);
 
+    // Test the "Add child" link for two siblings.
+    $this->verifyAddChildLink($item5);
+    $this->verifyAddChildLink($item6);
+
     // Move link and verify that descendants are updated.
     $this->moveMenuLink($item2, $item5->getPluginId(), $menu_name);
     // Hierarchy
@@ -787,7 +791,7 @@ public function addInvalidMenuLink() {
    */
   public function checkInvalidParentMenuLinks() {
     $last_link = NULL;
-    $created_links = [];
+    $plugin_ids = [];
 
     // Get the max depth of the tree.
     $menu_link_tree = \Drupal::service('menu.link_tree');
@@ -810,18 +814,28 @@ public function checkInvalidParentMenuLinks() {
       $this->submitForm($edit, 'Save');
       $menu_links = \Drupal::entityTypeManager()->getStorage('menu_link_content')->loadByProperties(['title' => $title]);
       $last_link = reset($menu_links);
-      $created_links[] = 'tools:' . $last_link->getPluginId();
+      $plugin_ids[] = $last_link->getPluginId();
     }
 
+    $last_plugin_id = array_pop($plugin_ids);
+
     // The last link cannot be a parent in the new menu link form.
     $this->drupalGet('admin/structure/menu/manage/tools/add');
-    $value = 'tools:' . $last_link->getPluginId();
+    $value = 'tools:' . $last_plugin_id;
     $this->assertSession()->optionNotExists('edit-menu-parent', $value);
 
     // All but the last link can be parents in the new menu link form.
-    array_pop($created_links);
-    foreach ($created_links as $key => $link) {
-      $this->assertSession()->optionExists('edit-menu-parent', $link);
+    foreach ($plugin_ids as $plugin_id) {
+      $this->assertSession()->optionExists('edit-menu-parent', 'tools:' . $plugin_id);
+    }
+
+    // The last link does not have an "Add child" operation.
+    $this->drupalGet('admin/structure/menu/manage/tools');
+    $this->assertSession()->linkByHrefNotExists('parent=' . urlencode($last_plugin_id));
+
+    // All but the last link do have an "Add child" operation.
+    foreach ($plugin_ids as $plugin_id) {
+      $this->assertSession()->linkByHrefExists('parent=' . urlencode($plugin_id));
     }
   }
 
@@ -909,6 +923,25 @@ public function modifyMenuLink(MenuLinkContent $item) {
     $this->assertSession()->pageTextContains($title);
   }
 
+  /**
+   * Verifies that the "Add child" link selects the correct parent item.
+   *
+   * @param \Drupal\menu_link_content\Entity\MenuLinkContent $item
+   *   Menu link entity.
+   */
+  public function verifyAddChildLink(MenuLinkContent $item): void {
+    $menu_name = $item->getMenuName();
+
+    $this->drupalGet('admin/structure/menu/manage/' . $menu_name);
+    $links = $this->xpath('//a[normalize-space()=:item_label]/following::a[normalize-space()=:link_label]', [
+      ':item_label' => $item->getTitle(),
+      ':link_label' => 'Add child',
+    ]);
+    $links[0]->click();
+    $option = $this->assertSession()->optionExists('edit-menu-parent', $menu_name . ':' . $item->getPluginId());
+    $this->assertTrue($option->isSelected());
+  }
+
   /**
    * Resets a standard menu link using the UI.
    *