wa_advice.module.php

<?php

/**
 * @file
 * Contains wa_advice.module.
 */

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\node\Entity\NodeType;
use Drupal\Core\Form\FormStateInterface;
use Drupal\node\NodeTypeInterface;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\Display\EntityViewDisplayInterface;

/**
 * Implements hook_help().
 */
function wa_advice_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    // Main module help for the wa_advice module.
    case 'help.page.wa_advice':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('W&amp;A Advice features') . '</p>';
      return $output;

    default:
  }
}

/**
 * Implements hook_theme().
 */
function wa_advice_theme() {
  $themes = [];

  return $themes;
}

/**
 * Implements hook_entity_extra_field_info().
 */
function wa_advice_entity_extra_field_info() {
  $extra = [];

  $bundles = NodeType::loadMultiple();
  $bundles = array_filter($bundles, function(NodeTypeInterface $bundle){
    return $bundle->getThirdPartySetting('wa_advice', 'extra_fields_enabled') == 1;
  });

  foreach ($bundles as $bundle) {
    /** @var $bundle NodeTypeInterface */

    $extra['node'][$bundle->Id()]['display']['created_date'] = [
      'label' => t('Create date'),
      'description' => t('@bundle create date', ['@bundle' => $bundle->label()]),
      'weight' => 100,
      'visible' => TRUE,
    ];
    $extra['node'][$bundle->Id()]['display']['editing_date'] = [
      'label' => t('Editing date'),
      'description' => t('@bundle edit date', ['@bundle' => $bundle->label()]),
      'weight' => 100,
      'visible' => TRUE,
    ];
  }

  return $extra;
}

/**
 * Implements hook_ENTITY_TYPE_view().
 */
function wa_advice_node_view(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display, $view_mode) {

  $format = 'created_edited';
  /** @var $entity  \Drupal\node\NodeInterface */
  if ($display->getComponent('created_date')) {
    $timestamp = $entity->getCreatedTime();
    $build['created_date'] = [
      '#type' => 'html_tag',
      '#tag' => 'span',
      '#value' => \Drupal::service('date.formatter')->format($timestamp, $format),
    ];
  }

  if ($display->getComponent('editing_date')) {
    $timestamp = $entity->get('changed')->value;
    $build['editing_date'] = [
      '#type' => 'html_tag',
      '#tag' => 'span',
      '#value' => \Drupal::service('date.formatter')->format($timestamp, $format),
    ];
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function wa_advice_form_node_type_form_alter(&$form, FormStateInterface $form_state, $form_id) {

  $node_type = $form_state->getFormObject()->getEntity();

  $form['display']['wa_extra_fields_enabled'] = array(
    '#type' => 'checkbox',
    '#title' => t('View extra fields'),
    '#description' => t('Check this box if you would enabled extra fields.'),
    '#default_value' => $node_type->getThirdPartySetting('wa_advice', 'extra_fields_enabled', 0),
  );
  $form['#entity_builders'][] = 'wa_advice_form_node_type_form_builder';
}

/**
 * Entity form builder for the node type form to map some values to third party
 * settings
 */
function wa_advice_form_node_type_form_builder($entity_type, NodeTypeInterface $type, &$form, FormStateInterface $form_state) {
  if ($form_state->getValue('wa_extra_fields_enabled') === 1) {
    $type->setThirdPartySetting('wa_advice', 'extra_fields_enabled', 1);
    return;
  }
  $type->unsetThirdPartySetting('wa_advice', 'extra_fields_enabled');
}