Update file SyndicationItem.php

By adding the parent_fid property explicitly and ensuring the batch processing code does not rely on dynamic properties, this should resolve the deprecation warning and ensure compatibility with the latest version of the Core Batch API.

src/Feeds/Item/BaseItem.php

@@ -7,18 +7,68 @@ namespace Drupal\feeds\Feeds\Item;
  */
 abstract class BaseItem implements ItemInterface {
 
+  /**
+   * Additional item data.
+   *
+   * This contains data for fields that are not defined as class properties.
+   *
+   * Subclasses MUST NOT override this property with a different type.
+   *
+   * @var array
+   */
+  protected array $data = [];
+
   /**
    * {@inheritdoc}
    */
   public function get($field) {
-    return $this->$field ?? NULL;
+    // Special case: allow "data" as a user field. When a field called 'data'
+    // is requested, instead of returning the contents of the $data property,
+    // check if the $data property contains a field called 'data'. If so, return
+    // that. If not, return null.
+    if ($field === 'data') {
+      return $this->data['data'] ?? NULL;
+    }
+
+    // Check if the requested field is defined as a property on our object. If
+    // this is the case, return the value of the object property.
+    if (property_exists($this, $field)) {
+      return $this->$field;
+    }
+
+    // If the field is *not* defined as an object property, check if the field
+    // exists on the data property.
+    if (isset($this->data[$field])) {
+      return $this->data[$field];
+    }
+
+    // The requested field was not found directly on the object, nor on the data
+    // property. In that case, return null.
+    return NULL;
   }
 
   /**
    * {@inheritdoc}
    */
   public function set($field, $value) {
-    $this->$field = $value;
+    // Special case: allow "data" as a user field.
+    // Store it inside the internal $data array instead of overwriting the $data
+    // property.
+    if ($field === 'data') {
+      $this->data['data'] = $value;
+      return $this;
+    }
+
+    // Check if the requested field is defined as a property on our object. If
+    // this is the case, set the value directly on that object property.
+    if (property_exists($this, $field)) {
+      $this->$field = $value;
+      return $this;
+    }
+
+    // If the field is *not* defined as an object property, set it on the data
+    // property.
+    $this->data[$field] = $value;
     return $this;
   }
 
@@ -26,7 +76,18 @@ abstract class BaseItem implements ItemInterface {
    * {@inheritdoc}
    */
   public function toArray() {
-    return get_object_vars($this);
+    $vars = [];
+
+    // Create an array of all object properties *except* $data.
+    foreach (get_object_vars($this) as $key => $value) {
+      if ($key !== 'data') {
+        $vars[$key] = $value;
+      }
+    }
+
+    // Merge with the internal $data array (which may also include a field
+    // called 'data').
+    return $vars + $this->data;
   }
 
   /**