Para todo lo que necesita solucionar ese problema, debe anular el método de proceso para que la clase Mage_SalesRule_Model_Validator sea como se muestra a continuación
public function process(Mage_Sales_Model_Quote_Item_Abstract $item)
{
$item->setDiscountAmount(0);
$item->setBaseDiscountAmount(0);
$item->setDiscountPercent(0);
$quote = $item->getQuote();
$address = $this->_getAddress($item);
$itemPrice = $this->_getItemPrice($item);
$baseItemPrice = $this->_getItemBasePrice($item);
$itemOriginalPrice = $this->_getItemOriginalPrice($item);
$baseItemOriginalPrice = $this->_getItemBaseOriginalPrice($item);
if ($itemPrice < 0) {
return $this;
}
$appliedRuleIds = array();
$this->_stopFurtherRules = false;
foreach ($this->_getRules() as $rule) {
/* @var $rule Mage_SalesRule_Model_Rule */
if (!$this->_canProcessRule($rule, $address)) {
continue;
}
if (!$rule->getActions()->validate($item)) {
continue;
}
$qty = $this->_getItemQty($item, $rule);
$rulePercent = min(100, $rule->getDiscountAmount());
$discountAmount = 0;
$baseDiscountAmount = 0;
//discount for original price
$originalDiscountAmount = 0;
$baseOriginalDiscountAmount = 0;
switch ($rule->getSimpleAction()) {
case Mage_SalesRule_Model_Rule::TO_PERCENT_ACTION:
$rulePercent = max(0, 100-$rule->getDiscountAmount());
//no break;
case Mage_SalesRule_Model_Rule::BY_PERCENT_ACTION:
$step = $rule->getDiscountStep();
if ($step) {
$qty = floor($qty/$step)*$step;
}
$_rulePct = $rulePercent/100;
$discountAmount = ($qty * $itemPrice - $item->getDiscountAmount()) * $_rulePct;
$baseDiscountAmount = ($qty * $baseItemPrice - $item->getBaseDiscountAmount()) * $_rulePct;
//get discount for original price
$originalDiscountAmount = ($qty * $itemOriginalPrice - $item->getDiscountAmount()) * $_rulePct;
$baseOriginalDiscountAmount =
($qty * $baseItemOriginalPrice - $item->getDiscountAmount()) * $_rulePct;
if (!$rule->getDiscountQty() || $rule->getDiscountQty()>$qty) {
$discountPercent = min(100, $item->getDiscountPercent()+$rulePercent);
$item->setDiscountPercent($discountPercent);
}
break;
case Mage_SalesRule_Model_Rule::TO_FIXED_ACTION:
$quoteAmount = $quote->getStore()->convertPrice($rule->getDiscountAmount());
$discountAmount = $qty * ($itemPrice-$quoteAmount);
$baseDiscountAmount = $qty * ($baseItemPrice-$rule->getDiscountAmount());
//get discount for original price
$originalDiscountAmount = $qty * ($itemOriginalPrice-$quoteAmount);
$baseOriginalDiscountAmount = $qty * ($baseItemOriginalPrice-$rule->getDiscountAmount());
break;
case Mage_SalesRule_Model_Rule::BY_FIXED_ACTION:
$step = $rule->getDiscountStep();
if ($step) {
$qty = floor($qty/$step)*$step;
}
$quoteAmount = $quote->getStore()->convertPrice($rule->getDiscountAmount());
$discountAmount = $qty * $quoteAmount;
$baseDiscountAmount = $qty * $rule->getDiscountAmount();
break;
case Mage_SalesRule_Model_Rule::CART_FIXED_ACTION:
if (empty($this->_rulesItemTotals[$rule->getId()])) {
Mage::throwException(Mage::helper('salesrule')->__('Item totals are not set for rule.'));
}
/**
* prevent applying whole cart discount for every shipping order, but only for first order
*/
if ($quote->getIsMultiShipping()) {
$usedForAddressId = $this->getCartFixedRuleUsedForAddress($rule->getId());
if ($usedForAddressId && $usedForAddressId != $address->getId()) {
break;
} else {
$this->setCartFixedRuleUsedForAddress($rule->getId(), $address->getId());
}
}
$cartRules = $address->getCartFixedRules();
if (!isset($cartRules[$rule->getId()])) {
$cartRules[$rule->getId()] = $rule->getDiscountAmount();
}
if ($cartRules[$rule->getId()] > 0) {
if ($this->_rulesItemTotals[$rule->getId()]['items_count'] <= 1) {
$quoteAmount = $quote->getStore()->convertPrice($cartRules[$rule->getId()]);
$baseDiscountAmount = min($baseItemPrice * $qty, $cartRules[$rule->getId()]);
} else {
$discountRate = $baseItemPrice * $qty /
$this->_rulesItemTotals[$rule->getId()]['base_items_price'];
$maximumItemDiscount = $rule->getDiscountAmount() * $discountRate;
$quoteAmount = $quote->getStore()->convertPrice($maximumItemDiscount);
$baseDiscountAmount = min($baseItemPrice * $qty, $maximumItemDiscount);
$this->_rulesItemTotals[$rule->getId()]['items_count']--;
}
$discountAmount = min($itemPrice * $qty, $quoteAmount);
$discountAmount = $quote->getStore()->roundPrice($discountAmount);
$baseDiscountAmount = $quote->getStore()->roundPrice($baseDiscountAmount);
//get discount for original price
$originalDiscountAmount = min($itemOriginalPrice * $qty, $quoteAmount);
$baseOriginalDiscountAmount = $quote->getStore()->roundPrice($baseItemOriginalPrice);
$cartRules[$rule->getId()] -= $baseDiscountAmount;
}
$address->setCartFixedRules($cartRules);
break;
case Mage_SalesRule_Model_Rule::BUY_X_GET_Y_ACTION:
$x = $rule->getDiscountStep();
$y = $rule->getDiscountAmount();
if (!$x || $y > $x) {
break;
}
$buyAndDiscountQty = $x + $y;
$fullRuleQtyPeriod = floor($qty / $buyAndDiscountQty);
$freeQty = $qty - $fullRuleQtyPeriod * $buyAndDiscountQty;
$discountQty = $fullRuleQtyPeriod * $y;
if ($freeQty > $x) {
$discountQty += $freeQty - $x;
}
$discountAmount = $discountQty * $itemPrice;
$baseDiscountAmount = $discountQty * $baseItemPrice;
//get discount for original price
$originalDiscountAmount = $discountQty * $itemOriginalPrice;
$baseOriginalDiscountAmount = $discountQty * $baseItemOriginalPrice;
break;
}
$result = new Varien_Object(array(
'discount_amount' => $discountAmount,
'base_discount_amount' => $baseDiscountAmount,
));
Mage::dispatchEvent('salesrule_validator_process', array(
'rule' => $rule,
'item' => $item,
'address' => $address,
'quote' => $quote,
'qty' => $qty,
'result' => $result,
));
$discountAmount = $result->getDiscountAmount();
$baseDiscountAmount = $result->getBaseDiscountAmount();
$percentKey = $item->getDiscountPercent();
/**
* Process "delta" rounding
*/
if ($percentKey) {
$delta = isset($this->_roundingDeltas[$percentKey]) ? $this->_roundingDeltas[$percentKey] : 0;
$baseDelta = isset($this->_baseRoundingDeltas[$percentKey])
? $this->_baseRoundingDeltas[$percentKey]
: 0;
$discountAmount += $delta;
$baseDiscountAmount += $baseDelta;
$this->_roundingDeltas[$percentKey] = $discountAmount -
$quote->getStore()->roundPrice($discountAmount);
$this->_baseRoundingDeltas[$percentKey] = $baseDiscountAmount -
$quote->getStore()->roundPrice($baseDiscountAmount);
$discountAmount = $quote->getStore()->roundPrice($discountAmount);
$baseDiscountAmount = $quote->getStore()->roundPrice($baseDiscountAmount);
} else {
$discountAmount = $quote->getStore()->roundPrice($discountAmount);
$baseDiscountAmount = $quote->getStore()->roundPrice($baseDiscountAmount);
}
/**
* We can't use row total here because row total not include tax
* Discount can be applied on price included tax
*/
$itemDiscountAmount = $item->getDiscountAmount();
$itemBaseDiscountAmount = $item->getBaseDiscountAmount();
$discountAmount = min($itemDiscountAmount + $discountAmount, $itemPrice * $qty);
$baseDiscountAmount = min($itemBaseDiscountAmount + $baseDiscountAmount, $baseItemPrice * $qty);
$item->setDiscountAmount($discountAmount);
$item->setBaseDiscountAmount($baseDiscountAmount);
$item->setOriginalDiscountAmount($originalDiscountAmount);
$item->setBaseOriginalDiscountAmount($baseOriginalDiscountAmount);
$appliedRuleIds[$rule->getRuleId()] = $rule->getRuleId();
$this->_maintainAddressCouponCode($address, $rule);
$this->_addDiscountDescription($address, $rule);
if ($rule->getStopRulesProcessing()) {
$this->_stopFurtherRules = true;
break;
}
}
$item->setAppliedRuleIds(join(',',$appliedRuleIds));
$address->setAppliedRuleIds($this->mergeIds($address->getAppliedRuleIds(), $appliedRuleIds));
$quote->setAppliedRuleIds($this->mergeIds($quote->getAppliedRuleIds(), $appliedRuleIds));
return $this;
}