/** * Check if this a duplicate rule creation request * * @param Mage_Tax_Model_Calculation_Rule $ruleModel * @return bool */ protected function _isValidRuleRequest($ruleModel) { $existingRules = $ruleModel->fetchRuleCodes($ruleModel->getTaxRate(), $ruleModel->getTaxCustomerClass(), $ruleModel->getTaxProductClass()); //Remove the current one from the list $existingRules = array_diff($existingRules, array($ruleModel->getCode())); //Verify if a Rule already exists. If not throw an error if (count($existingRules) > 0) { $ruleCodes = implode(",", $existingRules); $this->_getSingletonModel('adminhtml/session')->addError($this->_getHelperModel('tax')->__('Rules (%s) already exist for the specified Tax Rate, Customer Tax Class and Product Tax Class combinations', $ruleCodes)); return false; } return true; }