User Extender (prepareGroups functionality) (#2110)

src/User/User.php

@@ -83,6 +83,12 @@ class User extends AbstractModel
      */
     protected $session;
 
+    /**
+     * An array of callables, through each of which the user's list of groups is passed
+     * before being returned.
+     */
+    protected static $groupProcessors = [];
+
     /**
      * An array of registered user preferences. Each preference is defined with
      * a key, and its value is an array containing the following keys:.
@@ -660,8 +666,13 @@ class User extends AbstractModel
             $groupIds = array_merge($groupIds, [Group::MEMBER_ID], $this->groups->pluck('id')->all());
         }
 
+        // Deprecated, remove in beta 14.
         event(new PrepareUserGroups($this, $groupIds));
 
+        foreach (static::$groupProcessors as $processor) {
+            $groupIds = $processor($this, $groupIds);
+        }
+
         return Permission::whereIn('group_id', $groupIds);
     }
 
@@ -751,6 +762,17 @@ class User extends AbstractModel
         static::$preferences[$key] = compact('transformer', 'default');
     }
 
+    /**
+     * Register a callback that processes a user's list of groups.
+     *
+     * @param callable $callback
+     * @return array $groupIds
+     */
+    public static function addGroupProcessor($callback)
+    {
+        static::$groupProcessors[] = $callback;
+    }
+
     /**
      * Get the key for a preference which flags whether or not the user will
      * receive a notification for $type via $method.

src/User/UserServiceProvider.php

@@ -31,6 +31,10 @@ class UserServiceProvider extends AbstractServiceProvider
     {
         $this->registerAvatarsFilesystem();
         $this->registerDisplayNameDrivers();
+
+        $this->app->singleton('flarum.user.group_processors', function () {
+            return [];
+        });
     }
 
     protected function registerDisplayNameDrivers()
@@ -72,6 +76,14 @@ class UserServiceProvider extends AbstractServiceProvider
      */
     public function boot()
     {
+        foreach ($this->app->make('flarum.user.group_processors') as $callback) {
+            if (is_string($callback)) {
+                $callback = $this->app->make($callback);
+            }
+
+            User::addGroupProcessor($callback);
+        }
+
         User::setHasher($this->app->make('hash'));
         User::setGate($this->app->make(Gate::class));
         User::setDisplayNameDriver($this->app->make('flarum.user.display_name.driver'));