protected function generateDependencyData($cache)
    {
        $timestamps = $this->getTimestamps($cache, (array) $this->tags);

        $newKeys = [];
        foreach ($timestamps as $key => $timestamp) {
            if ($timestamp === false) {
                $newKeys[] = $key;
            }
        }
        if (!empty($newKeys)) {
            $timestamps = array_merge($timestamps, $this->touchKeys($cache, $newKeys));
        }

        return $timestamps;
    }