Custom Option Price Calculation Method

Question

Can someone explain why a custom option of type percent is calculated using the final item price on a quote?

See here:

# File: app/code/core/Mage/Catalog/Model/Product/Option/Value.php
public function getPrice($flag=false)
{
    if ($flag && $this->getPriceType() == 'percent') {
        $basePrice = $this->getOption()->getProduct()->getFinalPrice();
        $price = $basePrice*($this->_getData('price')/100);
        return $price;
    }
    return $this->_getData('price');
}

It doesn't seem to make sense to do this. Here's an example to illustrate the problem:

Laptop Computer
---
  Price: 500.00

  Custom Options
  ---
  1-YR Warranty: 20%

As I attempt to add this item to my cart along with the warranty option, my total cost as shown on the product view page will be 600.00. That looks good, because 20% is applied to the final price of 600.00 at that moment (100.00).

But what happens in the cart if this method is called, after the option has already been applied to the item?

According to the getPrice method above, it will show as 120.00 (20% of 600.00) ... clearly this is not right. And curiously, a stock installation of CE 1.x does not render custom option prices in the cart (only row totals).

Has anybody encountered this before? Or maybe more likely, what am I not understanding correctly here?

Answer 1

This shouldn't happen. The method Mage_Catalog_Model_Product_Option_Value::getPrice() is called during calculation of the products final price. At the beginning of this calculation "final_price" is set to the base price (1) and then incrementally modified, this includes adding option prices (2):

    /**
     * Get product final price
     *
     * @param   double $qty
     * @param   Mage_Catalog_Model_Product $product
     * @return  double
     */
    public function getFinalPrice($qty = null, $product)
    {
        if (is_null($qty) && !is_null($product->getCalculatedFinalPrice())) {
            return $product->getCalculatedFinalPrice();
        }

(1)===> $finalPrice = $this->getBasePrice($product, $qty); <===
        $product->setFinalPrice($finalPrice);
        Mage::dispatchEvent('catalog_product_get_final_price', array('product' => $product, 'qty' => $qty));
        $finalPrice = $product->getData('final_price');

(2)===> $finalPrice = $this->_applyOptionsPrice($product, $qty, $finalPrice); <===
        $finalPrice += $this->getTotalBundleItemsPrice($product, $qty);

        $product->setFinalPrice($finalPrice);
        return max(0, $product->getData('final_price'));
    }

Update

For those who don't read comments and want an answer to why the "final price" is used to convert the custom option percent amount: The percentage is actually based upon the base price with applied catalog price rules (or any other rules that custom extensions apply with the event catalog_product_get_final_price. This is not the final final price.

Answer 2

<?php
 $productSku = $_product->getSku();
 $product = Mage::getModel('catalog/product');
 $productId = $product->getIdBySku( $productSku );
 $product = Mage::getModel("catalog/product")->load($_product->getId());
 $attVal = $product->getOptions();
 $optStr = "";
?>
<div class="actions">

    <form action="<?php echo $this->getSubmitUrl($_product) ?>" method="post" id="product_addtocart_form"<?php if($_product->getOptions()): ?> enctype="multipart/form-data"<?php endif; ?>>
        <?php echo $this->getBlockHtml('formkey') ?>
        <div class="no-display">
            <input type="hidden" name="product" value="<?php echo $_product->getId() ?>" />
            <input type="hidden" name="related_product" id="related-products-field" value="" />
        </div>
       <?php $product = Mage::getModel('catalog/product'); ?>
    <?php $product->load($_product->getId()); ?>

 <?php foreach($attVal as $optionKey => $optionVal)
{
  $optStr.='<dt><label>'.$optionVal->getTitle().'</label></dt>';
  $optStr.= "<select style='display:block; clear:both;' id='".$optionVal->getId()."' name='options[".$optionVal->getId()."]'>";
  foreach($optionVal->getValues() as $valuesKey => $valuesVal)
{
$price = number_format($valuesVal->getPrice(),0);
$optStr.= "<option price='".number_format($valuesVal->getPrice(),0)."' data-label='".$colorarray[$valuesVal->getTitle()]."' value='".$valuesVal->getId()."'>".$valuesVal->getTitle(); if($price != '1'){$optStr.=" - Rs.".number_format($valuesVal->getPrice(),2);}$optStr.="&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</option>";
}
$optStr.= "</select>";
}
echo($optStr );
?>
 <?php if($_product->isSaleable()):?>
  <input type="image" src="<?php echo $this->getSkinUrl('images/addtocart.png')?>" class="button btn-cart" onclick="addToCart('<?php echo $this->getAddToCartUrl($_product) ?>')">

<?php else:?>
     <p class="availability out-of-stock"><span><?php echo $this->__('Out of stock')?></span></p>
 <?php endif;?>

 </form>
 </div>