MAGETWO-39117: Updating qty that exceeds the qty in stock for registered customer by API should return error

moved error processing to the quote scope.

Author: Serhiy Shkolyarenko

app/code/Magento/Quote/Model/Quote/Item/CartItemPersister.php

@@ -72,12 +72,6 @@ public function save(CartInterface $quote, CartItemInterface $item)
                     $item = $quote->updateItem($itemId, $buyRequestData);
                 } else {
                     $currentItem->setQty($qty);
-                    if (!empty($currentItem->getErrorInfos())) {
-                        $errors = $currentItem->getErrorInfos();
-                        /** @var \Magento\Framework\Message\MessageInterface $error */
-                        $errorData = array_shift($errors);
-                        throw new CouldNotSaveException($errorData['message']);
-                    }
                 }
             } else {
                 /** add new item to shopping cart */

app/code/Magento/Quote/Model/QuoteRepository/SaveHandler.php

@@ -7,6 +7,7 @@
 
 use Magento\Quote\Api\Data\CartInterface;
 use Magento\Framework\Exception\InputException;
+use Magento\Framework\Exception\CouldNotSaveException;
 
 class SaveHandler
 {
@@ -70,6 +71,13 @@ public function save(CartInterface $quote)
                 }
             }
         }
+        $errors = $quote->getErrors();
+        if (!empty($errors)) {
+            $renderedErrors = $this->renderErrors($errors);
+            throw new CouldNotSaveException(
+                __('Following errors occurred on save: %1', implode('; ', $renderedErrors))
+            );
+        }
 
         // Billing Address processing
         $billingAddress = $quote->getBillingAddress();
@@ -83,6 +91,21 @@ public function save(CartInterface $quote)
         return $quote;
     }
 
+    /**
+     * @param array $errors
+     * @return array
+     */
+    private function renderErrors($errors)
+    {
+        $renderedErrors = [];
+        /** @var \Magento\Framework\Message\Error $error */
+        foreach ($errors as $error) {
+            $renderedErrors[] = $error->getText();
+        }
+        return $renderedErrors;
+    }
+
+
     /**
      * @param \Magento\Quote\Model\Quote $quote
      * @return void