MAGETWO-39051: Wrong behavior for required "Customer Address Attributes" during checkout

Author: Olexii Korshenko

app/code/Magento/Checkout/Block/Checkout/LayoutProcessor.php

@@ -48,7 +48,7 @@ public function process($jsLayout)
         /** @var \Magento\Eav\Api\Data\AttributeInterface[] $attributes */
         $attributes = $this->attributeMetadataDataProvider->loadAttributesCollection(
             'customer_address',
-            'customer_register_address'
+            'customer_address_edit'
         );
 
         $elements = [];

app/code/Magento/Checkout/Controller/Onepage.php

@@ -180,14 +180,14 @@ protected function _expireAjax()
     {
         $quote = $this->getOnepage()->getQuote();
         if (!$quote->hasItems() || $quote->getHasError() || !$quote->validateMinimumAmount()) {
-            return false;
+            return true;
         }
         $action = $this->getRequest()->getActionName();
         if ($this->_objectManager->get('Magento\Checkout\Model\Session')->getCartWasUpdated(true)
             &&
             !in_array($action, ['index', 'progress'])
         ) {
-            return false;
+            return true;
         }
 
         return false;

app/code/Magento/Checkout/view/frontend/web/js/action/select-shipping-address.js

@@ -14,8 +14,8 @@ define(
         });
         return function(shippingAddress) {
             quote.shippingAddress(shippingAddress);
-            //set billing address same as shipping by default
-            if (shippingAddress.canUseForBilling()) {
+            //set billing address same as shipping by default if it is not empty
+            if (shippingAddress.countryId != undefined && shippingAddress.canUseForBilling()) {
                 quote.billingAddress(shippingAddress);
             }
         };