class LayoutBuilderHtmlEntityFormController

class LayoutBuilderHtmlEntityFormController extends FormController {
    use DependencySerializationTrait;
    
    /**
     * The entity form controller being decorated.
     *
     * @var \Drupal\Core\Controller\FormController
     */
    protected $entityFormController;
    
    /**
     * Constructs a LayoutBuilderHtmlEntityFormController object.
     *
     * @param \Drupal\Core\Controller\FormController $entity_form_controller
     *   The entity form controller being decorated.
     */
    public function __construct(FormController $entity_form_controller) {
        $this->entityFormController = $entity_form_controller;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContentResult(Request $request, RouteMatchInterface $route_match) {
        $form = $this->entityFormController
            ->getContentResult($request, $route_match);
        // If the form render element has a #layout_builder_element_keys property,
        // first set the form element as a child of the root render array. Use the
        // keys to get the layout builder element from the form render array and
        // copy it to a separate child element of the root element to prevent any
        // forms within the layout builder element from being nested.
        if (isset($form['#layout_builder_element_keys'])) {
            $build['form'] =& $form;
            $layout_builder_element =& NestedArray::getValue($form, $form['#layout_builder_element_keys']);
            $build['layout_builder'] = $layout_builder_element;
            // Remove the layout builder element within the form.
            $layout_builder_element = [];
            return $build;
        }
        // If no #layout_builder_element_keys property, return form as is.
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getFormArgument(RouteMatchInterface $route_match) {
        return $this->entityFormController
            ->getFormArgument($route_match);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getFormObject(RouteMatchInterface $route_match, $form_arg) {
        return $this->entityFormController
            ->getFormObject($route_match, $form_arg);
    }

}