Magento 2 – Apply Free Shipping Coupon Code for Specific Shipping Method

My suggestion is to remove coupon code form from cart table footer and add it above Totals table.

Edit cart.phtml file under your theme template app/design/frontend/custom_package/custom_theme/template/checkout/cart.phtml and add the following code within this div <div class="cartRow"> before <div class="cartRight">:

<div class="cartRight" style="margin-bottom: 20px;">
    <?php echo $this->getChildHtml('coupon') ?>
</div>

The output should look like this screenshot:

In your custom module, add the following to config.xml:

<models>
    <salesrule>
        <rewrite>
            <quote_discount>Namespace_Module_Rewrite_SalesRule_Model_Quote_Discount</quote_discount>
        </rewrite>
    </salesrule>
</models>
<frontend>
    <routers>
        <checkout>
            <args>
                <modules>
                    <Namespace_Module before="Mage_Checkout">Namespace_Module_Checkout</Namespace_Module>
                </modules>
            </args>
        </checkout>
    </routers>
</frontend>

The first is a rewrite of Mage_SalesRule_Model_Quote_Discount to Namespace_Module_Rewrite_SalesRule_Model_Quote_Discount

The second is the overloaded controller Mage_Checkout_CartController

Next add the following file app/code/community/Namespace/Module/controllers/Checkout/CartController.php and insert the following code:

<?php

require_once 'Mage/Checkout/controllers/CartController.php';

class Namespace_Module_Checkout_CartController extends Mage_Checkout_CartController
{
    /**
     * Initialize coupon
     */
    public function couponPostAction()
    {
        /**
         * No reason continue with empty shopping cart
         */
        if (!$this->_getCart()->getQuote()->getItemsCount()) {
            $this->_goBack();
            return;
        }

        $couponCode = (string) $this->getRequest()->getParam('coupon_code');
        if ($this->getRequest()->getParam('remove') == 1) {
            $couponCode = '';
        }
        $oldCouponCode = $this->_getQuote()->getCouponCode();

        if (!strlen($couponCode) && !strlen($oldCouponCode)) {
            $this->_goBack();
            return;
        }

        try {
            $codeLength = strlen($couponCode);
            $isCodeLengthValid = $codeLength && $codeLength <= Mage_Checkout_Helper_Cart::COUPON_CODE_MAX_LENGTH;

            // Combine multiple coupons
            $couponFlag = true;

            if ($isCodeLengthValid) {
                $del = ',';

                if ($oldCouponCode) {

                    if ($oldCouponCode == $couponCode) {
                        $couponCode = $oldCouponCode;
                    } else {
                        $couponCode = $oldCouponCode . $del . $couponCode;
                    }
                }
            } else {
                $couponCode = '';
            }

            $this->_getQuote()->getShippingAddress()->setCollectShippingRates(true);
            $this->_getQuote()->setCouponCode($couponCode)
                ->collectTotals()
                ->save();

            if ($codeLength) {
                if ($isCodeLengthValid && $couponFlag) {
                    $this->_getSession()->addSuccess(
                        $this->__('Coupon code "%s" was applied.', Mage::helper('core')->escapeHtml($couponCode))
                    );
                } else {
                    $this->_getSession()->addError(
                        $this->__('Coupon code "%s" is not valid.', Mage::helper('core')->escapeHtml($couponCode))
                    );
                }
            } else {
                $this->_getSession()->addSuccess($this->__('Coupon code was canceled.'));
            }

        } catch (Mage_Core_Exception $e) {
            $this->_getSession()->addError($e->getMessage());
        } catch (Exception $e) {
            $this->_getSession()->addError($this->__('Cannot apply the coupon code.'));
            Mage::logException($e);
        }

        $this->_goBack();
    }
}

You will notice i added a section to combine coupon codes delimited by ",". This can obviously be more refined and you may want to add additional checking etc, but this code should work straight off the bat.

And finally we need to add the piece that does all the magic. Add the file app/code/community/Namespace/Module/Rewrite/SalesRule/Model/Quote/Discount.php

and add the content:

<?php

class Namespace_Module_Rewrite_SalesRule_Model_Quote_Discount extends Mage_SalesRule_Model_Quote_Discount
{
    /**
     * Collect address discount amount
     *
     * @param   Mage_Sales_Model_Quote_Address $address
     * @return  Mage_SalesRule_Model_Quote_Discount
     */
    public function collect(Mage_Sales_Model_Quote_Address $address)
    {
        Mage_Sales_Model_Quote_Address_Total_Abstract::collect($address);
        $quote = $address->getQuote();
        $store = Mage::app()->getStore($quote->getStoreId());
        $this->_calculator->reset($address);

        $items = $this->_getAddressItems($address);
        if (!count($items)) {
            return $this;
        }

        $couponCode = $quote->getCouponCode();
        $couponArray = explode(',',$couponCode);

        foreach ($couponArray as $couponCode) {
            $this->_calculator->init($store->getWebsiteId(), $quote->getCustomerGroupId(), $couponCode);
            $this->_calculator->initTotals($items, $address);

            $eventArgs = array(
                'website_id'        => $store->getWebsiteId(),
                'customer_group_id' => $quote->getCustomerGroupId(),
                'coupon_code'       => $couponCode,
            );

            $address->setDiscountDescription(array());
            $items = $this->_calculator->sortItemsByPriority($items);
            foreach ($items as $item) {
                if ($item->getNoDiscount()) {
                    $item->setDiscountAmount(0);
                    $item->setBaseDiscountAmount(0);
                }
                else {
                    /**
                     * Child item discount we calculate for parent
                     */
                    if ($item->getParentItemId()) {
                        continue;
                    }

                    $eventArgs['item'] = $item;
                    Mage::dispatchEvent('sales_quote_address_discount_item', $eventArgs);

                    if ($item->getHasChildren() && $item->isChildrenCalculated()) {
                        foreach ($item->getChildren() as $child) {
                            $this->_calculator->process($child);
                            $eventArgs['item'] = $child;
                            Mage::dispatchEvent('sales_quote_address_discount_item', $eventArgs);

                            $this->_aggregateItemDiscount($child);
                        }
                    } else {
                        $this->_calculator->process($item);
                        $this->_aggregateItemDiscount($item);
                    }
                }
            }

            /**
             * process weee amount
             */
            if (Mage::helper('weee')->isEnabled() && Mage::helper('weee')->isDiscounted($store)) {
                $this->_calculator->processWeeeAmount($address, $items);
            }

            /**
             * Process shipping amount discount
             */
            $address->setShippingDiscountAmount(0);
            $address->setBaseShippingDiscountAmount(0);
            if ($address->getShippingAmount()) {
                $this->_calculator->processShippingAmount($address);
                $this->_addAmount(-$address->getShippingDiscountAmount());
                $this->_addBaseAmount(-$address->getBaseShippingDiscountAmount());
            }

            $this->_calculator->prepareDescription($address);
        }

        return $this;
    }
}

Basically, what this does is breaks the coupon sting up, loops through each coupon code, calculates and updates the quote totals.

To test, i have setup 2 shopping cart rules:

• test 1 - 10 % product price discount - Stop Further Rules Processing: No
• test 2 - 10 % product price discount - Stop Further Rules Processing: No

No coupon:

Added coupon test 1:

Added coupon test 2

I have tested with fixed amount discount and this works as expected as well.

And like i said, you may need to add additional checking, possibly for duplicates, but this is where you would start. For the frontend, you could add some logic split the codes however you prefer or leave as is.