MAGETWO-69657: Credit Card Information disappear after user enters promotion code

- Fix code formatting and documentation
- Deep clone methodList to prevent side-effects in getAvailablePaymentMethods method
- Fix cc-form and paypal-express test mocks

Author: Michael Yu

app/code/Magento/Checkout/view/frontend/web/js/model/payment-service.js

@@ -7,8 +7,9 @@ define([
     'underscore',
     'Magento_Checkout/js/model/quote',
     'Magento_Checkout/js/model/payment/method-list',
-    'Magento_Checkout/js/action/select-payment-method'
-], function (_, quote, methodList, selectPaymentMethod) {
+    'Magento_Checkout/js/action/select-payment-method',
+    'mage/utils/objects'
+], function (_, quote, methodList, selectPaymentMethod, utils) {
     'use strict';
 
     var freeMethodCode = 'free';
@@ -21,7 +22,6 @@ define([
          * @param {Array} methods
          */
         setPaymentMethods: function (methods) {
-
             var freeMethod,
                 filteredMethods,
                 methodIsAvailable,
@@ -36,6 +36,7 @@ define([
                 methods.splice(0, methods.length, freeMethod);
                 selectPaymentMethod(freeMethod);
             }
+
             filteredMethods = _.without(methods, freeMethod);
 
             if (filteredMethods.length === 1) {
@@ -71,20 +72,26 @@ define([
          * @returns {Array}
          */
         getAvailablePaymentMethods: function () {
-            var allMethods = methodList(),
+            var allMethods = utils.copy(methodList()),
+
+                /**
+                 * Free method filter
+                 * @param {Object} method
+                 */
                 isFreeMethod = function (method) {
                     return method.method === freeMethodCode;
                 },
                 grandTotalOverZero = quote.totals().grand_total > 0;
 
             if (!self.isFreeAvailable) {
                 return allMethods;
-            } else if (grandTotalOverZero) {
+            }
+
+            if (grandTotalOverZero) {
                 return _.filter(allMethods, _.negate(isFreeMethod));
-            } else {
-                return _.filter(allMethods, isFreeMethod);
             }
 
+            return _.filter(allMethods, isFreeMethod);
         }
     };
 });

dev/tests/js/jasmine/tests/app/code/Magento/Braintree/frontend/js/view/payment/method-renderer/cc-form.test.js

@@ -18,7 +18,8 @@ define([
                 'Magento_Checkout/js/model/quote': {
                     billingAddress: ko.observable(),
                     shippingAddress: ko.observable(),
-                    paymentMethod: ko.observable()
+                    paymentMethod: ko.observable(),
+                    totals: ko.observable({})
                 },
                 'Magento_Braintree/js/view/payment/validator-handler': jasmine.createSpyObj(
                     'validator-handler',

dev/tests/js/jasmine/tests/app/code/Magento/Paypal/frontend/js/view/payment/method-renderer/paypal-express-abstract.test.js

@@ -20,7 +20,9 @@ define([
                 'Magento_Checkout/js/model/quote': {
                     billingAddress: ko.observable(),
                     shippingAddress: ko.observable(),
-                    paymentMethod: ko.observable()
+                    paymentMethod: ko.observable(),
+                    totals: ko.observable({})
+
                 }
             },
             paypalExpressAbstract,