Issue #3227314 by Mauro_, hmendes, irinaz, andregp, j-vee, daften, gbirch,...

Issue #3227314 by Mauro_, hmendes, irinaz, andregp, j-vee, daften, gbirch, lucienchalom: Checkbox-fields are unchecked when editing nodes with multi-value checkbox List-fields

src/Element/Buttons.php

@@ -79,8 +79,8 @@ class Buttons extends ElementBase {
    *   The select or other element.
    */
   protected static function addEmptyOption(array &$element) {
-    if (!isset($element['#no_empty_option']) || !$element['#no_empty_option']) {
-      if (!$element['#multiple'] && !$element['#required'] && !empty($element['#default_value'])) {
+    if ((!isset($element['#no_empty_option']) || !$element['#no_empty_option']) && !$element['#multiple']) {
+      if (!$element['#required'] && !empty($element['#default_value'])) {
         $element['select']['#options'] = ['' => t('- None -')] + $element['select']['#options'];
       }
       else {

tests/src/Unit/ButtonsElementTest.php

@@ -73,7 +73,6 @@ class ButtonsElementTest extends UnitTestBase {
     $expected_element = array_merge_recursive($base_expected_element, [
       'select' => [
         '#type' => 'checkboxes',
-        '#value' => [],
       ],
       'other' => [
         '#states' => [