metatag-8.x-1.x-dev/tests/modules/metatag_test_custom_route/metatag_test_custom_route.module

<?php

/**
 * @file
 * Contains metatag_test_custom_route.module..
 */

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\StringTranslation\TranslatableMarkup;

/**
 * Implements hook_help().
 */
function metatag_test_custom_route_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    // Main module help for the metatag_test_custom_route module.
    case 'help.page.metatag_test_custom_route':
      $output = '';
      $output .= '<h3>' . (string) new TranslatableMarkup('About') . '</h3>';
      $output .= '<p>' . (string) new TranslatableMarkup('Support module for testing handling of a custom route.') . '</p>';
      return $output;

    default:
  }
}

/**
 * Implements hook_metatag_route_entity().
 */
function metatag_test_custom_route_metatag_route_entity(RouteMatchInterface $route_match) {
  if ($route_match->getRouteName() === 'metatag_test_custom_route.entity_route') {
    if ($entity_test = $route_match->getParameter('entity_test')) {
      return $entity_test;
    }
  }
}