public FormBuilder::prepareForm($form_id, &$form, FormStateInterface &a

public FormStateDecoratorBase::setTemporaryValue($key

public FormStateInterface::setHasFileElement($has_file_element

public FormState::setRebuildInfo(array $rebuild_info) Sets

public FormStateDecoratorBase::setValidationEnforced($must_validate

protected FormBase::getRouteMatch() Gets the

public FormStateDecoratorBase::getAlwaysProcess()

public FormStateDecoratorBase::setRebuild($rebuild = TRUE)

public FormInterface::validateForm(array &$form, FormStateInterface

hook_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) Perform alterations