Move in visibility scoping from tags, add automated testing.

extensions/flags/src/Access/ScopeFlagVisibility.php

@@ -0,0 +1,59 @@
+<?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\Flags\Access;
+
+use Flarum\Extension\ExtensionManager;
+use Flarum\Tags\Tag;
+use Flarum\User\User;
+use Illuminate\Database\Eloquent\Builder;
+
+class ScopeFlagVisibility
+{
+    /**
+     * @var ExtensionManager
+     */
+    protected $extensions;
+
+    public function __construct(ExtensionManager $extensions)
+    {
+        $this->extensions = $extensions;
+    }
+
+    public function __invoke(User $actor, Builder $query)
+    {
+        if ($this->extensions->isEnabled('flarum-tags')) {
+            $query
+                ->select('flags.*')
+                ->leftJoin('posts', 'posts.id', '=', 'flags.post_id')
+                ->leftJoin('discussions', 'discussions.id', '=', 'posts.discussion_id')
+                ->whereNotExists(function ($query) use ($actor) {
+                    return $query->selectRaw('1')
+                        ->from('discussion_tag')
+                        ->whereNotIn('tag_id', function ($query) use ($actor) {
+                            Tag::query()->setQuery($query->from('tags'))->whereHasPermission($actor, 'discussion.viewFlags')->select('tags.id');
+                        })
+                        ->whereColumn('discussions.id', 'discussion_id');
+                });
+
+            if (!$actor->hasPermission('discussion.viewFlags')) {
+                $query->whereExists(function ($query) use ($actor) {
+                    return $query->selectRaw('1')
+                        ->from('discussion_tag')
+                        ->whereColumn('discussions.id', 'discussion_id');
+                });
+            }
+        }
+
+
+        if (!$actor->hasPermission('discussion.viewFlags')) {
+            $query->orWhere('flags.user_id', $actor->id);
+        }
+    }
+}