Issue #3218877: Labels do not have correct 'for' attribute if 'id' set in #attributes

core/lib/Drupal/Core/Form/FormBuilder.php

@@ -977,6 +977,17 @@ public function doBuildForm($form_id, &$element, FormStateInterface &$form_state
       $element['#array_parents'] = [];
     }
 
+    if (!empty($element['#attributes']['id']) && is_array($element['#attributes']['id'])) {
+      @trigger_error('Providing IDs as an array is deprecated in drupal:9.3.0 and is removed in drupal:10.0.0. Only use string values for ID.', E_USER_DEPRECATED);
+      $element['#attributes']['id'] = reset($element['#attributes']['id']);
+    }
+
+    // If an ID is set in #attributes, copy to $element['#id'] as there is
+    // rendering logic that only checks there for explicitly set IDs.
+    if (!isset($element['#id']) && !empty($element['#attributes']['id'])) {
+      $element['#id'] = $element['#attributes']['id'];
+    }
+
     if (!isset($element['#id'])) {
       $unprocessed_id = 'edit-' . implode('-', $element['#parents']);
       $element['#id'] = Html::getUniqueId($unprocessed_id);