NodeForm::actions

protected NodeForm::actions(array $form, FormStateInterface $form_state)

protected function actions(array $form, FormStateInterface $form_state) {
  $element = parent::actions($form, $form_state);
  $node = $this->entity;
  $preview_mode = $node->type->entity->getPreviewMode();

  $element['submit']['#access'] = $preview_mode != DRUPAL_REQUIRED || $this->hasBeenPreviewed;

  // If saving is an option, privileged users get dedicated form submit
  // buttons to adjust the publishing status while saving in one go.
  // @todo This adjustment makes it close to impossible for contributed
  //   modules to integrate with "the Save operation" of this form. Modules
  //   need a way to plug themselves into 1) the ::submit() step, and
  //   2) the ::save() step, both decoupled from the pressed form button.
  if ($element['submit']['#access'] && \Drupal::currentUser()->hasPermission('administer nodes')) {
    // isNew | prev status » default   & publish label             & unpublish label
    // 1     | 1           » publish   & Save and publish          & Save as unpublished
    // 1     | 0           » unpublish & Save and publish          & Save as unpublished
    // 0     | 1           » publish   & Save and keep published   & Save and unpublish
    // 0     | 0           » unpublish & Save and keep unpublished & Save and publish

    // Add a "Publish" button.
    $element['publish'] = $element['submit'];
    // If the "Publish" button is clicked, we want to update the status to "published".
    $element['publish']['#published_status'] = TRUE;
    $element['publish']['#dropbutton'] = 'save';
    if ($node->isNew()) {
      $element['publish']['#value'] = t('Save and publish');
    }
    else {
      $element['publish']['#value'] = $node->isPublished() ? t('Save and keep published') : t('Save and publish');
    }
    $element['publish']['#weight'] = 0;

    // Add a "Unpublish" button.
    $element['unpublish'] = $element['submit'];
    // If the "Unpublish" button is clicked, we want to update the status to "unpublished".
    $element['unpublish']['#published_status'] = FALSE;
    $element['unpublish']['#dropbutton'] = 'save';
    if ($node->isNew()) {
      $element['unpublish']['#value'] = t('Save as unpublished');
    }
    else {
      $element['unpublish']['#value'] = !$node->isPublished() ? t('Save and keep unpublished') : t('Save and unpublish');
    }
    $element['unpublish']['#weight'] = 10;

    // If already published, the 'publish' button is primary.
    if ($node->isPublished()) {
      unset($element['unpublish']['#button_type']);
    }
    // Otherwise, the 'unpublish' button is primary and should come first.
    else {
      unset($element['publish']['#button_type']);
      $element['unpublish']['#weight'] = -10;
    }

    // Remove the "Save" button.
    $element['submit']['#access'] = FALSE;
  }

  $element['preview'] = array(
    '#type' => 'submit',
    '#access' => $preview_mode != DRUPAL_DISABLED && ($node->access('create') || $node->access('update')),
    '#value' => t('Preview'),
    '#weight' => 20,
    '#submit' => array('::submitForm', '::preview'),
  );

  $element['delete']['#access'] = $node->access('delete');
  $element['delete']['#weight'] = 100;

  return $element;
}