Issue #3301062 by rp7: Show error message when selecting a second reference...

Issue #3301062 by rp7: Show error message when selecting a second reference without a first reference

src/Plugin/Field/FieldWidget/DoubleReferenceAutocompleteSelectWidget.php

@@ -6,6 +6,7 @@ use Drupal\Core\Field\FieldFilteredMarkup;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\Plugin\Field\FieldWidget\EntityReferenceAutocompleteWidget;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * Provides an autocomplete/select widget for the double_reference field type.
@@ -72,6 +73,11 @@ class DoubleReferenceAutocompleteSelectWidget extends EntityReferenceAutocomplet
       $widget['ar_target_id']['#title_display'] = 'before';
     }
 
+    $widget['#element_validate'][] = [
+      static::class,
+      'validateElement',
+    ];
+
     return $widget;
   }
 
@@ -111,4 +117,21 @@ class DoubleReferenceAutocompleteSelectWidget extends EntityReferenceAutocomplet
     return $options;
   }
 
+  /**
+   * Validates the element.
+   *
+   * @param array $element
+   *   The form element.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   */
+  public static function validateElement(array $element, FormStateInterface $form_state) {
+    if (empty($element['target_id']['#value']) && !empty($element['ar_target_id']['#value'])) {
+      $form_state->setError($element['target_id'], new TranslatableMarkup('%field is required when %ar_field has a value.', [
+        '%field' => $element['target_id']['#title'],
+        '%ar_field' => $element['ar_target_id']['#title'],
+      ]));
+    }
+  }
+
 }

src/Plugin/Field/FieldWidget/DoubleReferenceAutocompleteWidget.php

@@ -5,6 +5,7 @@ namespace Drupal\double_reference\Plugin\Field\FieldWidget;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\Plugin\Field\FieldWidget\EntityReferenceAutocompleteWidget;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 
 /**
  * Provides an autocomplete widget for the double_reference field type.
@@ -69,7 +70,29 @@ class DoubleReferenceAutocompleteWidget extends EntityReferenceAutocompleteWidge
       $widget['ar_target_id']['#title_display'] = 'before';
     }
 
+    $widget['#element_validate'][] = [
+      static::class,
+      'validateElement',
+    ];
+
     return $widget;
   }
 
+  /**
+   * Validates the element.
+   *
+   * @param array $element
+   *   The form element.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The form state.
+   */
+  public static function validateElement(array $element, FormStateInterface $form_state) {
+    if (empty($element['target_id']['#value']) && !empty($element['ar_target_id']['#value'])) {
+      $form_state->setError($element['target_id'], new TranslatableMarkup('%field is required when %ar_field has a value.', [
+        '%field' => $element['target_id']['#title'],
+        '%ar_field' => $element['ar_target_id']['#title'],
+      ]));
+    }
+  }
+
 }