magento 2.4 check coupon in checkout page

Question

On my magento 2.4 I have a few coupon codes that should only be available to the admins via backend, which means that the customers on the frontend should not be able to use them. I was able to achieve this for the coupon block on the cart page by creating a Plugin on the \Magento\Checkout\Controller\Cart\CouponPost::execute() method. This method, however, doesnt work for the coupon block on the checkout page.

What I do on the cart page is:

• check the coupon code entered by the user
• if the coupon code is one of the restricted coupon codes
• then removes the coupon from the cart and shows an "invalid code" error message to the user

How can I do the same on the checkout page? So when the user inserts the restricted coupon and clicks apply, I need to be able to not apply that coupon and send an error message instead

Answer 1

Sorry for the late reply.. what i ended up doing is creating a mixin for the Magento_SalesRule/js/view/payment/discount. So:

• Vendor/Module/view/frontend/requirejs-config.js

var config = {
    config: {
        mixins: {
            'Magento_SalesRule/js/view/payment/discount': {
                'Vendor_Module/js/view/payment/discount-mixin': true
            }
        }
    }
};

• Vendor/Module/view/frontend/web/js/view/payment/discount-mixin.js

define(function() {
    'use strict';
    return function(target) {
        return target.extend({
            apply: function () {
                var tempCouponCode = JSON.stringify(this.couponCode());
                if( tempCouponCode.toLowerCase().indexOf($restrictedCouponCode) === -1 
                ) {
                        return this._super(); // calls the original method
                }
            },
        });
    }
});

Hope it helps