Pierre Dureau
--- a/src/Element/Pattern.php
+++ b/src/Element/Pattern.php
+   * @param array $element
+   *   Render array.
+   *
+   * @return array
+   *   Render array.
+   */
+  public static function processFieldAttributes(array $element) {
+    $definition = UiPatterns::getPatternDefinition($element['#id']);
+    $fields = $definition->getFields();
+    foreach ($fields as $field_id => $field_definition) {
+      if (!\is_array($element['#' . $field_id])) {
+        continue;
+      }
+      $add_class = $field_definition->getClassesToAdd();
+      if (empty($add_class)) {
+        continue;