Issue #3012629: Group dragging feature lost in 8.x-1.2

src/DraggableViews.php

@@ -3,6 +3,7 @@
 namespace Drupal\draggableviews;
 
 use Drupal\media\Entity\Media;
+use Drupal\node\Entity\Node;
 use Drupal\views\ViewExecutable;
 use Drupal\Component\Utility\Html;
 
@@ -11,6 +12,13 @@ use Drupal\Component\Utility\Html;
  */
 class DraggableViews {
 
+  /**
+   * Already indexed ids.
+   *
+   * @var array
+   */
+  protected $ids;
+
   /**
    * The view.
    *
@@ -25,6 +33,7 @@ class DraggableViews {
    *   Views object.
    */
   public function __construct(ViewExecutable $view) {
+    $this->ids = [];
     $this->view = $view;
   }
 
@@ -37,11 +46,19 @@ class DraggableViews {
         // Media index name.
         $name = 'mid';
       }
-      else {
-        // Node index name. The default one.
+      elseif ($item->_entity instanceof Node) {
+        // Node index name.
         $name = 'nid';
       }
-      if ($item->$name == $id) {
+      else {
+        // The default one.
+        $name = 'id';
+      }
+
+      if (property_exists($item, $name) && $item->$name == $id) {
+        if (!in_array($id, $this->ids)) {
+          $this->ids[] = $id;
+        }
         return $item->index;
       }
     }