public function findMissingDependencies()
    {
        $missing = [];

        foreach ($this->plugins as $id => $plugin) {
            if (!$required = $this->getDependencies($plugin)) {
                continue;
            }

            foreach ($required as $require) {
                if ($this->hasPlugin($require)) {
                    continue;
                }

                if (!in_array($require, $missing)) {
                    $missing[] = $require;
                }
            }
        }

        return $missing;
    }