Onepage Checkout – Fixing Stuck on Billing Section Issue

So just to let those who have similar issues know, the problem was with the GeoLocation Currency Converter extension. It did override some files, but more importantly, the review variable was not defined in templates/checkout/onepage/review.phtml. Uninstalling the extension and restoring some template files did the trick.

Okay, no responses so hopefully the following may help some poor soul who finds themselves in the same boat I was in. Credit for helping me track down the issue goes to this post on TechyTalk.info. The solution outlined there didn't apply in my case as I wasn't dealing with price rules or creating orders in the backend. However, it did help me pinpoint what I need to be concerned about, so big thanks for that! To summarize:

When using a custom totals collector, Magento's _afterLoad() method in Mage_Sales_Model_Quote can cause an excessive call to collectTotals() after a product has been modified. The call to collectTotals() is managed by the trigger_recollect flag which, is set to 1 when the product has been modified. Fine in most cases but not when certain events are triggered!

The first thing collectTotals() in Mage_Sales_Model_Quote does is to wipe out (set to zero) all of the quote totals and then call collectTotals() on all address objects it can get its hands on (Mage_Sales_Model_Quote_Address). As it turns out, however, when _afterLoad() is called on certain events after a product is modified, there are no address objects available and the quote total remains at zero when collectTotals() completes.

The second scenario I described was just a result of the way our code worked where, when a product was removed from the cart (and Magento reported that it's total price is zero), the Ajax method did not update the checkout page totals since, according to it's logic, the cart total had not changed (a zero-price product was removed).

I inspected the quote object and, unfortunately, could not find a property with which I could detect that the trigger_recollect flag has been set at product save. In addition, my custom totals collector had already re-calculated the totals in each instance that I could test for so I simply temporarily turned off the trigger_recollect while calling the parent::_afterload() in a descendant class to at least allow all other processing and events dispatched to proceed as expected. This fixed the issue in both scenarios.

Mock override:

class Some_Other_Model_Sales_Quote extends Mage_Sales_Model_Quote
{
    //... some other stuff here

    /**
     * Bypass the collectTotals() call in Mage_Sales_Model_Quote
     *
     * This still triggers all the _afterLoad() events and processing
     *
     * @return Mage_Core_Model_Abstract
     */
    protected function _afterLoad()
    {
        $triggerRecollect = $this->getTriggerRecollect();
        $this->setTriggerRecollect(false);
        $return = parent::_afterLoad();
        $this->setTriggerRecollect($triggerRecollect);
        return $return;
    }
}