BooleanCheckboxWidget doesn't respect #required_error

Changes are made on on 11.x (our main development branch) first, and are then back ported as needed according to our policies.

Really change to 11.x

christian.wiedemann → changed the visibility of the branch 3423819-booleancheckboxwidget-doesnt-respect to hidden.

Can we get a test case showing the problem.

Getting this error after applying latest MR. Seems like validateElement method needs to be added in Widget.

The website encountered an unexpected error. Try again later.

TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class Drupal\Core\Field\Plugin\Field\FieldWidget\BooleanCheckboxWidget does not have a method "validateElement" in call_user_func_array() (line 283 of core/lib/Drupal/Core/Form/FormValidator.php).
Drupal\Core\Form\FormValidator->doValidateForm() (Line: 239)
Drupal\Core\Form\FormValidator->doValidateForm() (Line: 239)
Drupal\Core\Form\FormValidator->doValidateForm() (Line: 239)
Drupal\Core\Form\FormValidator->doValidateForm() (Line: 118)
Drupal\Core\Form\FormValidator->validateForm() (Line: 585)
Drupal\Core\Form\FormBuilder->processForm() (Line: 321)
Drupal\Core\Form\FormBuilder->buildForm() (Line: 73)
Drupal\Core\Controller\FormController->getContentResult()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 622)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 121)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 183)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 116)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 90)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 53)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 715)
Drupal\Core\DrupalKernel->handle() (Line: 19)

Updated issue description as it appears to be copied from other issue