protected function getPlugins(): array
    {
        if ($this->plugins) {
            return $this->plugins;
        }

        // Load WordPress's plugin helper functions.
        require_once ABSPATH.'wp-admin/includes/plugin.php';

        $plugins = array_diff_key(
            get_plugins('/'.$this->getRelativePath()),
            get_mu_plugins()
        );

        $this->plugins = array_unique($plugins, SORT_REGULAR);

        return $this->plugins;
    }