Drupal 8+ How to rename existing route path using route_event_subscriber

Drupal 8

krishna kanth, Credit to volkotech-solutions Dec 21

To modify an existing route in Drupal 8, you can use the route_event_subscriber event and the route_build event.
Here's an example of how you can modify the route '/user-example/code' to '/u/code':

Clear the cache after enabling the module to apply the changes.

Keep in mind that this is just an example and you may need to modify the code to fit your specific use case.

UserExampleRouteSubscriber.php

<?php
use Drupal\Core\Routing\RouteSubscriberBase;
use Symfony\Component\Routing\RouteCollection;

/**
 * Modifies the route for '/user-example/code'.
 */
class UserExampleRouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection) {
    // Check if the route exists in the collection.
    if ($route = $collection->get('user_example.code')) {
      // Modify the route path.
      $route->setPath('/u/code');
    }
    
    /* Check if the page matches
    $current_path = \Drupal::request()->getPathInfo();
    if ($current_path == '/user-example/code') {
      // Do something.
    }
    */
  }

}

services.yml

services:
  user_example.route_subscriber:
    class: Drupal\user_example\Routing\UserExampleRouteSubscriber
    tags:
      - { name: event_subscriber }