Issue #3457701: MaterialIcons::getFormIconField returns null causing ajax error.

Closes #3457701

src/Plugin/Field/FieldWidget/MaterialIcons.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\material_icons\Plugin\Field\FieldWidget;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Config\ConfigFactory;
 use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemListInterface;
@@ -126,7 +127,7 @@ class MaterialIcons extends WidgetBase implements ContainerFactoryPluginInterfac
     $cardinality = $this->fieldDefinition->getFieldStorageDefinition()->getCardinality();
 
     // Gets font family from $form_state, if available.
-    $font_family = $this->getFormStateFontFamily($form_state)
+    $font_family = $this->getFormStateFontFamily($form, $form_state)
       ??
       ($items[$delta]->get('family')->getValue()
         ??
@@ -196,61 +197,40 @@ class MaterialIcons extends WidgetBase implements ContainerFactoryPluginInterfac
    *   The form element to be updated.
    */
   public function handleIconStyleUpdated(array &$form, FormStateInterface $form_state) {
-    return $this->getFormIconField($form, $form_state);
+    $element = $this->getElement($form, $form_state);
+    return $element['icon'] ?? NULL;
   }
 
   /**
-   * Gets the underlying field name of the triggering element.
+   * Gets the selected value of the font family.
    *
    * @param array $form
    *   The form where the settings form is being included in.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The form state of the (entire) configuration form.
    *
-   * @return array|Null
-   *   The form element to be updated.
-   */
-  private function getFormIconField(array $form, FormStateInterface $form_state): array|Null {
-    $parents = $this->getFormStateStructure($form_state);
-    return !is_null($parents) ? $form[$parents[3]][$parents[2]][$parents[1]]['icon'] : NULL;
-  }
-
-  /**
-   * Gets the selected value of the font family.
-   *
-   * @param \Drupal\Core\Form\FormStateInterface $form_state
-   *   The form state of the (entire) configuration form.
-   *
    * @return string|Null
    *   This is the array structure being delivered:
    */
-  private function getFormStateFontFamily(FormStateInterface $form_state): string|Null {
-    $parents = $this->getFormStateStructure($form_state);
-    return !is_null($parents) ? $form_state->getValue($parents[3])[$parents[1]]['family'] : NULL;
+  private function getFormStateFontFamily(array &$form, FormStateInterface $form_state): string|Null {
+    $element = $this->getElement($form, $form_state);
+    return $element['family'] ?? NULL;
   }
 
   /**
-   * Gets the selected value of the font family.
+   * Gets the element.
    *
+   * @param array $form
+   *   The form where the settings form is being included in.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The form state of the (entire) configuration form.
    *
    * @return array|Null
-   *   This is the array structure being delivered:
-   *     0 => 'family'
-   *     1 => [delta integer]
-   *     2 => 'widget'
-   *     3 => [original field name]
+   *   The array structure being delivered.
    */
-  private function getFormStateStructure(FormStateInterface $form_state): array|Null {
-    $triggering_element = $form_state->getTriggeringElement();
-
-    if (empty($triggering_element)) {
-      return NULL;
-    }
-
-    $parents = array_reverse($triggering_element['#array_parents']);
-    return array_key_exists(1, $parents) && array_key_exists(3, $parents) ? $parents : NULL;
+  private function getElement(array &$form, FormStateInterface $form_state): array|Null {
+    $trigger = $form_state->getTriggeringElement();
+    return $trigger ? NestedArray::getValue($form, array_slice($trigger['#array_parents'], 0, -1)) : NULL;
   }
 
   /**