MC-34793: Coupon code based on shipping method remains applied after shipping method changed to another one

Author: nikita-shcherbatykh

app/code/Magento/SalesRule/view/frontend/requirejs-config.js

@@ -8,6 +8,9 @@ var config = {
         mixins: {
             'Magento_Checkout/js/action/select-payment-method': {
                 'Magento_SalesRule/js/action/select-payment-method-mixin': true
+            },
+            'Magento_Checkout/js/model/shipping-save-processor': {
+                'Magento_SalesRule/js/model/shipping-save-processor-mixin': true
             }
         }
     }

app/code/Magento/SalesRule/view/frontend/web/js/model/shipping-save-processor-mixin.js

@@ -0,0 +1,34 @@
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+define([
+    'mage/utils/wrapper',
+    'Magento_Checkout/js/model/quote',
+    'Magento_SalesRule/js/model/coupon'
+], function (wrapper, quote, coupon) {
+    'use strict';
+
+    return function (shippingSaveProcessor) {
+        shippingSaveProcessor.saveShippingInformation = wrapper.wrapSuper(
+            shippingSaveProcessor.saveShippingInformation,
+            function (type) {
+                var updateCouponCallback;
+
+                /**
+                 * Update coupon form
+                 */
+                updateCouponCallback = function () {
+                    if (quote.totals() && !quote.totals()['coupon_code']) {
+                        coupon.setCouponCode('');
+                        coupon.setIsApplied(false);
+                    }
+                };
+
+                return this._super(type).done(updateCouponCallback);
+            }
+        );
+
+        return shippingSaveProcessor;
+    };
+});