1.6.17, Cart::getDeliveryOption uses internal cache that is never cleared during script lifetime

[Alexander.X]

Cart.php @2587

 public function getDeliveryOption($default_country = null, $dontAutoSelectOptions = false, $use_cache = true)
    {
        static $cache = array();
        $cache_id = (int)(is_object($default_country) ? $default_country->id : 0).'-'.(int)$dontAutoSelectOptions;
        if (isset($cache[$cache_id]) && $use_cache) {
            return $cache[$cache_id];
        }

        $delivery_option_list = $this->getDeliveryOptionList($default_country);

this 'static $cache' cache is never cleared during script lifetime.

Somehow it doesnt cause problems for standart theme, but I faced this problem while develop a custom checkout page - changing delivery method didnt work from time to time. Problem was fixed by using my own cache, that is CLEARED by setDeliveryOption and avoiding using this cache.

Below is my override-based solution:

// get/set DeliveryOption - fix caching issue (we SHOULD drop internal cache on setDeliveryOption)
    protected static $_deliveryOptionsCache = [];
    public function getDeliveryOption($default_country = null, $dontAutoSelectOptions = false, $use_cache = true) {
        $cache_id = (int)(is_object($default_country) ? $default_country->id : 0).'-'.(int)$dontAutoSelectOptions;
        if (isset(self::$_deliveryOptionsCache[$cache_id]) && $use_cache) {
            return self::$_deliveryOptionsCache[$cache_id];
        }
        self::$_deliveryOptionsCache[$cache_id] = parent::getDeliveryOption($default_country, $dontAutoSelectOptions, false); // disable builtin cache
        return self::$_deliveryOptionsCache[$cache_id];
    }

    public function setDeliveryOption($delivery_option = null) {
        self::$_deliveryOptionsCache = [];
        parent::setDeliveryOption($delivery_option);
    }