feat: Use an extensible document title driver implementation (#3109)

* feat: Use an extensible document title driver implementation
* chore: Add todo to use DI in 2.0

framework/core/tests/integration/extenders/FrontendTitleTest.php

@@ -0,0 +1,74 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\integration\extenders;
+
+use Flarum\Extend\Frontend;
+use Flarum\Frontend\Document;
+use Flarum\Frontend\Driver\TitleDriverInterface;
+use Flarum\Testing\integration\RetrievesAuthorizedUsers;
+use Flarum\Testing\integration\TestCase;
+use Psr\Http\Message\ServerRequestInterface;
+
+class FrontendTitleTest extends TestCase
+{
+    use RetrievesAuthorizedUsers;
+
+    protected function setUp(): void
+    {
+        $this->prepareDatabase([
+            'users' => [
+                $this->normalUser(),
+            ],
+            'discussions' => [
+                ['id' => 1, 'title' => 'Test Discussion', 'user_id' => 1, 'first_post_id' => 1]
+            ],
+            'posts' => [
+                ['id' => 1, 'discussion_id' => 1, 'user_id' => 2, 'type' => 'comment', 'content' => '<t><p>can i haz potat?</p></t>'],
+            ],
+        ]);
+
+        $this->setting('forum_title', 'Flarum');
+    }
+
+    /**
+     * @test
+     */
+    public function basic_title_driver_is_used_by_default()
+    {
+        $this->assertTitleEquals('Test Discussion - Flarum');
+    }
+
+    /**
+     * @test
+     */
+    public function custom_title_driver_works_if_set()
+    {
+        $this->extend((new Frontend('forum'))->title(CustomTitleDriver::class));
+
+        $this->assertTitleEquals('CustomTitle');
+    }
+
+    private function assertTitleEquals(string $title): void
+    {
+        $response = $this->send($this->request('GET', '/d/1'));
+
+        preg_match('/\<title\>(?<title>[^<]+)\<\/title\>/m', $response->getBody()->getContents(), $matches);
+
+        $this->assertEquals($title, $matches['title']);
+    }
+}
+
+class CustomTitleDriver implements TitleDriverInterface
+{
+    public function makeTitle(Document $document, ServerRequestInterface $request, array $forumApiDocument): string
+    {
+        return 'CustomTitle';
+    }
+}