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

added separate multimessage  exception

Author: Serhiy Shkolyarenko

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

@@ -7,7 +7,7 @@
 
 use Magento\Quote\Api\Data\CartInterface;
 use Magento\Framework\Exception\InputException;
-use Magento\Framework\Exception\CouldNotSaveException;
+use Magento\Framework\Exception\CouldNotSaveMultiMessageException;
 
 class SaveHandler
 {
@@ -73,10 +73,7 @@ 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))
-            );
+            throw new CouldNotSaveMultiMessageException('Following errors occurred on save: %1', $errors);
         }
 
         // Billing Address processing
@@ -91,21 +88,6 @@ 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

lib/internal/Magento/Framework/Exception/CouldNotSaveMultiMessageException.php

@@ -0,0 +1,43 @@
+<?php
+/**
+ * Copyright © 2016 Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Framework\Exception;
+
+use Magento\Framework\Phrase;
+
+class CouldNotSaveMultiMessageException extends CouldNotSaveException
+{
+    /**
+     * @param string $mainMessage
+     * @param \Magento\Framework\Message\Error[] $errors
+     * @param string $separator
+     */
+    public function __construct($mainMessage, $errors, $separator = '; ')
+    {
+        $renderedErrors = $this->renderErrors($errors, $separator);
+        // $mainMessage should contain %1 to be substituted by concatenated errors
+        $phrase = new \Magento\Framework\Phrase($mainMessage, [$renderedErrors]);
+        parent::__construct($phrase);
+    }
+
+    /**
+     * @param \Magento\Framework\Message\Error[] $errors
+     * @param string $separator
+     * @return string
+     */
+    private function renderErrors($errors, $separator)
+    {
+        $renderedErrors = '';
+        $eol = '';
+        /** @var \Magento\Framework\Message\Error $error */
+        foreach ($errors as $error) {
+            $renderedErrors .= $eol . __($error->getText())->render();
+            $eol = $separator;
+        }
+        return $renderedErrors;
+    }
+
+}