fix(channel): start a thread in a forum without throwing

src/Parts/ForumThread.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempcord\Discord\Parts;
+
+/**
+ * A post in a forum or media channel.
+ *
+ * A thread in every other respect, but Discord answers the call that creates
+ * one with the opening message attached — the only place a channel comes back
+ * carrying a message. That message is what reactions and edits address, so it
+ * is worth having a name rather than being reached for through a cast.
+ *
+ * @see https://discord.com/developers/docs/resources/channel#start-thread-in-forum-or-media-channel
+ */
+class ForumThread extends Channel
+{
+    public Message $message;
+}

src/Rest/Channel.php

@@ -8,6 +8,7 @@
 use Discord\Http\Multipart\MultipartBody;
 use Tempcord\Discord\Parts\ArchivedThreads;
 use Tempcord\Discord\Parts\Channel as PartsChannel;
+use Tempcord\Discord\Parts\ForumThread;
 use Tempcord\Discord\Parts\Invite;
 use Tempcord\Discord\Parts\Message;
 use Tempcord\Discord\Parts\ThreadMember;
@@ -699,24 +700,21 @@ public function startThreadWithoutMessage(
     /**
      * @see https://discord.com/developers/docs/resources/channel#start-thread-in-forum-or-media-channel
      *
-     * @return PromiseInterface<\Tempcord\Discord\Parts\Channel> includes $message property
+     * @return PromiseInterface<\Tempcord\Discord\Parts\ForumThread> the post, with
+     *         the opening message Discord answers with attached
      */
     public function startThreadInForumChannel(
         string $channelId,
         MultipartBody|array $params,
         ?string $reason = null
     ): PromiseInterface {
-        $forumChannelWithMessage = new class () extends Channel {
-            public Message $message;
-        };
-
         return $this->mapPromise(
             $this->http->post(
                 Endpoint::bind(Endpoint::CHANNEL_THREADS, $channelId),
                 $params,
                 $this->getAuditLogReasonHeader($reason),
             ),
-            $forumChannelWithMessage::class,
+            ForumThread::class,
         );
     }
 

tests/Rest/ChannelTest.php

@@ -5,6 +5,7 @@
 namespace Tests\Tempcord\Discord\Rest;
 
 use Tempcord\Discord\Parts\ArchivedThreads;
+use Tempcord\Discord\Parts\ForumThread;
 use Tempcord\Discord\Parts\Channel as PartsChannel;
 use Tempcord\Discord\Parts\Invite;
 use Tempcord\Discord\Parts\Message;
@@ -204,6 +205,20 @@ public static function httpBindingsProvider(): array
                     'returnType' => PartsChannel::class,
                 ]
             ],
+            'Start thread in forum channel' => [
+                'method' => 'startThreadInForumChannel',
+                'args' => ['::channel id::', ['name' => '::post::', 'message' => ['content' => '::text::']]],
+                'mockOptions' => [
+                    'method' => 'post',
+                    'return' => (object) [
+                        'id' => '::thread id::',
+                        'message' => (object) ['id' => '::message id::'],
+                    ],
+                ],
+                'validationOptions' => [
+                    'returnType' => ForumThread::class,
+                ]
+            ],
             'Delete channel' => [
                 'method' => 'delete',
                 'args' => ['::channel id::'],