PluginManager.php

<?php

namespace Drupal\lazy_route_provider_install_test;

use Drupal\Component\Annotation\PluginID;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Extension\ModuleHandlerInterface;
use Drupal\Core\Plugin\DefaultPluginManager;
use Drupal\Core\Routing\UrlGeneratorInterface;
use Drupal\Core\Url;
class PluginManager extends DefaultPluginManager {
    
    /**
     * PluginManager constructor.
     *
     * This plugin manager depends on the URL generator to ensure that this
     * service is instantiated during module installation when the plugin caches
     * are cleared.
     *
     * @param \Traversable $namespaces
     *   An object that implements \Traversable which contains the root paths
     *   keyed by the corresponding namespace to look for plugin implementations.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   A cache backend.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
     *   The URL generator.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, UrlGeneratorInterface $url_generator) {
        // Generate a URL during construction to prove that URL generation works. If
        // the route was missing an exception would be thrown. This also forces the
        // route provider to be initialized very early during a module install.
        \Drupal::state()->set(__CLASS__, Url::fromRoute('system.admin')->toString());
        parent::__construct('Plugin/LazyRouteProviderInstallTest', $namespaces, $module_handler, NULL, PluginID::class);
    }

}