Fix invisible posts when deleting first in series

extend.php

@@ -4,6 +4,7 @@
 
 use Flarum\Api\Serializer\PostSerializer;
 use Flarum\Extend;
+use Flarum\Post\Event\Deleted;
 use Flarum\Post\Event\Saving;
 use Flarum\Post\Post;
 
@@ -33,7 +34,8 @@
         ->attributes(PostAttributes::class),
 
     (new Extend\Event())
-        ->listen(Saving::class, Listener\SavePost::class),
+        ->listen(Saving::class, Listener\SavePost::class)
+        ->listen(Deleted::class, Listener\DeletePost::class),
 
     (new Extend\Policy())
         ->modelPolicy(Post::class, Access\PostPolicy::class),

src/Listener/DeletePost.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace ClarkWinkelmann\CollapsiblePosts\Listener;
+
+use ClarkWinkelmann\CollapsiblePosts\Job\UpdateCollapseCount;
+use Flarum\Post\Event\Deleted;
+use Illuminate\Contracts\Queue\Queue;
+
+class DeletePost
+{
+    protected $queue;
+
+    public function __construct(Queue $queue)
+    {
+        $this->queue = $queue;
+    }
+
+    public function handle(Deleted $event)
+    {
+        $discussion = $event->post->discussion;
+
+        // The relationship should still be able to load, but just in case we don't want to crash everything
+        if (!$discussion) {
+            return;
+        }
+
+        $this->queue->push(new UpdateCollapseCount($discussion));
+    }
+}