CRM_Member_Form.patch

  protected function setPriceSetParameters($formValues) {
    $this->_priceSetId = self::getPriceSetID($formValues);
    $priceSetDetails = self::getPriceSetDetails($formValues);
    $this->_priceSet = $priceSetDetails[$this->_priceSetId];

    // Call the buildAmount hook again to support extensions such as
    // cdntaxcalculator, otherwise we cannot customize tax calculations.
    // Setting the priceSetId this way is required by some extensions
    // such as CiviDiscount.
    $this->set('priceSetId', $this->_priceSetId);
    CRM_Utils_Hook::buildAmount('membership', $this, $this->_priceSet['fields']);

    // process price set and get total amount and line items.
    $this->ensurePriceParamsAreSet($formValues);
    return $formValues;
  }