specific error messages on coupon codes

Question

Is it possible to get the reason that a coupon code is invalid? For example, if I have a shopping cart rule that specifies that the order subtotal must be $100 or more, and the user tries to use the coupon on a subtotal that is only $75, could I show a message along the lines of "your cart must be $100 or more"?

Answer 1

Here's an approach that I took to put in a better error message for two specific filters: the from date and to date.

Those filters are pretty simple compared to digging into the actual rule conditions such as subtotal, as you've mentioned in your question, but I think still provide a significant usability improvement with a pretty straight forward implementation.

There are two pretty clean rewrites that can be done to accomplish this.

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Mage_SalesRule_Model_Resource_Rule_Collection::addWebsiteGroupDateFilter

Overload the addWebsiteGroupDateFilter method to prevent rules that don't match the date filter from being excluded entirely from the rules that are processed.

public function addWebsiteGroupDateFilter($websiteId, $customerGroupId, $now = null)
{
    parent::addWebsiteGroupDateFilter($websiteId, $customerGroupId, $now);

    $where = $this->_removeDateFilters();
    $this->getSelect()->setPart('where', $where);

    return $this;
}

protected function _removeDateFilters()
{
    $where = $this->getSelect()->getPart('where');

    foreach ($where as $index => $whereLine) {
        if (strpos($whereLine, "from_date is null or from_date <") !== false) {
            unset($where[$index]);
        } elseif (strpos($whereLine, "to_date is null or to_date >") !== false) {
            unset($where[$index]);
        }
    }

    $where = array_values($where);

    return $where;
}

Clean_Checkout_Model_SalesRule_Validator::_canProcessRule

Overload the _canProcessRule method to check the dates and add a specific error message to the session.

protected function _canProcessRule($rule, $address)
{
    if ($this->_isRuleExpired($rule, $address)) {
        return false;
    }

    return parent::_canProcessRule($rule, $address);
}

protected function _isRuleExpired($rule, $address)
{
    if ($rule->getFromDate() && date('Y-m-d', time()) < $rule->getFromDate()) {
        $message = "This coupon won't be active until {$rule->getFromDate()}";
        Mage::getSingleton('checkout/session')->addUniqueMessages(new Mage_Core_Model_Message_Error($message));

        return true;
    }

    if ($rule->getToDate() && date('Y-m-d', time()) > $rule->getToDate()) {
        $message = "This coupon expired on {$rule->getToDate()}";
        Mage::getSingleton('checkout/session')->addUniqueMessages(new Mage_Core_Model_Message_Error($message));

        return true;
    }
}

Answer 2

Not without customization. You'd have to write messages that tie into all of the different scenarios that the promotion rules could do (not a simple task by any means). That is most likely why the error message is pretty basic.

A suggestion solution for Magento developers. You could include a textarea description field in the promotion settings. This would allow the admin to include a customized message if the promotional rule fails, instead of showing a basic "Coupon code is invalid" message. This would be a quick solution rather than programmatically trying to assign a specific error message based on a set of rules.