--- /dev/null
+<?php
+
+namespace Drupal\url_alter_test;
+
+use Drupal\Core\PathProcessor\InboundPathProcessorInterface;
+use Drupal\Core\PathProcessor\OutboundPathProcessorInterface;
+use Drupal\Core\Render\BubbleableMetadata;
+use Symfony\Component\HttpFoundation\Request;
+use Drupal\user\Entity\User;
+
+/**
+ * Path processor for url_alter_test.
+ */
+class PathProcessorTest implements InboundPathProcessorInterface, OutboundPathProcessorInterface {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function processInbound($path, Request $request) {
+ // Rewrite user/username to user/uid.
+ if (preg_match('!^/user/([^/]+)(/.*)?!', $path, $matches)) {
+ if ($account = user_load_by_name($matches[1])) {
+ $matches += [2 => ''];
+ $path = '/user/' . $account->id() . $matches[2];
+ }
+ }
+
+ // Rewrite community/ to forum/.
+ $path = preg_replace('@^/community(.*)@', '/forum$1', $path);
+
+ if ($path == '/url-alter-test/bar') {
+ $path = '/url-alter-test/foo';
+ }
+ return $path;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function processOutbound($path, &$options = [], Request $request = NULL, BubbleableMetadata $bubbleable_metadata = NULL) {
+ // Rewrite user/uid to user/username.
+ if (preg_match('!^/user/([0-9]+)(/.*)?!', $path, $matches)) {
+ if ($account = User::load($matches[1])) {
+ $matches += [2 => ''];
+ $path = '/user/' . $account->getUsername() . $matches[2];
+ if ($bubbleable_metadata) {
+ $bubbleable_metadata->addCacheTags($account->getCacheTags());
+ }
+ }
+ }
+
+ // Verify that $options are alterable.
+ if ($path == '/user/login') {
+ $options['query']['foo'] = 'bar';
+ }
+
+ // Rewrite forum/ to community/.
+ return preg_replace('@^/forum(.*)@', '/community$1', $path);
+ }
+
+}