Issue #2774255 by joelpittet, lauriii: Allow form element to set attributes for label

core/includes/form.inc

@@ -432,6 +432,7 @@ function template_preprocess_form_element(&$variables) {
   $element += array(
     '#title_display' => 'before',
     '#wrapper_attributes' => array(),
+    '#label_attributes' => array(),
   );
   $variables['attributes'] = $element['#wrapper_attributes'];
 
@@ -479,6 +480,7 @@ function template_preprocess_form_element(&$variables) {
   $variables['label_display'] = $element['#title_display'];
   $variables['label'] = array('#theme' => 'form_element_label');
   $variables['label'] += array_intersect_key($element, array_flip(array('#id', '#required', '#title', '#title_display')));
+  $variables['label']['#attributes'] = $element['#label_attributes'];
 
   $variables['children'] = $element['#children'];
 }

core/modules/system/tests/src/Kernel/Form/FormElementLabelTest.php

@@ -31,6 +31,16 @@ public function testAttributes() {
     $this->render($render_array);
     $elements = $this->xpath($css_selector_converter->toXPath('.kitten'));
     $this->assertCount(1, $elements);
+
+    // Add label attributes to a form element.
+    $render_array = [
+      '#type' => 'textfield',
+      '#label_attributes' => ['class' => ['meow']],
+      '#title' => 'Kitten sounds',
+    ];
+    $this->render($render_array);
+    $elements = $this->xpath($css_selector_converter->toXPath('label.meow'));
+    $this->assertCount(1, $elements);
   }
 
 }