Keep tag discussions_count up-to-date

extensions/tags/src/Handlers/TagMetadataUpdater.php

@@ -0,0 +1,49 @@
+<?php namespace Flarum\Tags\Handlers;
+
+use Flarum\Tags\Tag;
+use Flarum\Tags\Events\DiscussionWasTagged;
+use Flarum\Core\Events\DiscussionWasStarted;
+use Flarum\Core\Events\DiscussionWasDeleted;
+use Flarum\Core\Models\Discussion;
+
+class TagMetadataUpdater
+{
+    public function subscribe($events)
+    {
+        $events->listen('Flarum\Core\Events\DiscussionWasStarted', __CLASS__.'@whenDiscussionWasStarted');
+        $events->listen('Flarum\Tags\Events\DiscussionWasTagged', __CLASS__.'@whenDiscussionWasTagged');
+        $events->listen('Flarum\Core\Events\DiscussionWasDeleted', __CLASS__.'@whenDiscussionWasDeleted');
+    }
+
+    public function whenDiscussionWasStarted(DiscussionWasStarted $event)
+    {
+        $tags = $event->discussion->tags();
+
+        $this->updateTagCounts($tags, 1);
+    }
+
+    public function whenDiscussionWasTagged(DiscussionWasTagged $event)
+    {
+        $oldTags = Tag::whereIn('id', array_pluck($event->oldTags, 'id'));
+
+        $this->updateTagCounts($oldTags, -1);
+
+        $newTags = $event->discussion->tags();
+
+        $this->updateTagCounts($newTags, 1);
+    }
+
+    public function whenDiscussionWasDeleted(DiscussionWasDeleted $event)
+    {
+        $tags = $event->discussion->tags();
+
+        $this->updateTagCounts($tags, -1);
+
+        $tags->detach();
+    }
+
+    protected function updateTagCounts($query, $delta)
+    {
+        $query->update(['discussions_count' => app('db')->raw('discussions_count + '.$delta)]);
+    }
+}

extensions/tags/src/Handlers/TagSaver.php

@@ -3,7 +3,6 @@
 use Flarum\Tags\Tag;
 use Flarum\Tags\Events\DiscussionWasTagged;
 use Flarum\Core\Events\DiscussionWillBeSaved;
-use Flarum\Core\Events\DiscussionWasDeleted;
 use Flarum\Core\Models\Discussion;
 use Flarum\Core\Exceptions\PermissionDeniedException;
 
@@ -12,7 +11,6 @@ class TagSaver
     public function subscribe($events)
     {
         $events->listen('Flarum\Core\Events\DiscussionWillBeSaved', __CLASS__.'@whenDiscussionWillBeSaved');
-        $events->listen('Flarum\Core\Events\DiscussionWasDeleted', __CLASS__.'@whenDiscussionWasDeleted');
     }
 
     public function whenDiscussionWillBeSaved(DiscussionWillBeSaved $event)
@@ -57,9 +55,4 @@ class TagSaver
             }
         }
     }
-
-    public function whenDiscussionWasDeleted(DiscussionWasDeleted $event)
-    {
-        $event->discussion->tags()->sync([]);
-    }
 }

extensions/tags/src/TagsServiceProvider.php

@@ -124,6 +124,7 @@ class TagsServiceProvider extends ServiceProvider
             // Add an event subscriber so that tags data is persisted when
             // saving a discussion.
             new Extend\EventSubscriber('Flarum\Tags\Handlers\TagSaver'),
+            new Extend\EventSubscriber('Flarum\Tags\Handlers\TagMetadataUpdater'),
 
             // Add a gambit that allows filtering discussions by tag(s).
             new Extend\DiscussionGambit('Flarum\Tags\TagGambit'),