Generate a URL template from a Drupal route name (with optional/partial parameter replacement).

GetUrlTemplateByRouteName.php

<?php

namespace Drupal\commons_core\Helper;

use http\Exception\InvalidArgumentException;

class GetUrlTemplateByRouteName {

  /**
   * Generate a URL template from a route.
   *
   * @param string $route_name , e.g. 'my_module.foo'
   * @param array $route_parameters Optional parameters if you wish to
   * subsitute tokens with real values.  Otherwise, the tokens remain in the
   * response.
   *
   * @return string The URL of the route with tokens (unless passed in
   * $route_parameters, in which case those are replaced.), e.g.
   * '/my-module/{uid}/foo'
   */
  public function __invoke(string $route_name, array $route_parameters = []): string {

    /** @var \Symfony\Component\Routing\Route $route */
    $route = \Drupal::service('router.route_provider')
      ->getRouteByName($route_name);
    $requirements = $route->getRequirements();
    if (array_diff_key($route_parameters, $requirements)) {
      throw new InvalidArgumentException('Invalid route parameters.');
    }
    $template = $route->getPath();
    $find = array_map(fn($key) => '{' . $key . '}', array_keys($route_parameters));
    $replace = array_values($route_parameters);

    return str_replace($find, $replace, $template);
  }
}