Fix libxml_use_internal_errors and libxml_disable_entity_loader usage

Author: romainneutron

Encoder/XmlEncoder.php

@@ -66,6 +66,10 @@ public function encode($data, $format, array $context = array())
      */
     public function decode($data, $format, array $context = array())
     {
+        if ('' === trim($data)) {
+            throw new UnexpectedValueException('Invalid XML data, it can not be empty.');
+        }
+
         $internalErrors = libxml_use_internal_errors(true);
         $disableEntities = libxml_disable_entity_loader(true);
         libxml_clear_errors();
@@ -77,6 +81,8 @@ public function decode($data, $format, array $context = array())
         libxml_disable_entity_loader($disableEntities);
 
         if ($error = libxml_get_last_error()) {
+            libxml_clear_errors();
+
             throw new UnexpectedValueException($error->message);
         }
 

Tests/Encoder/XmlEncoderTest.php

@@ -330,6 +330,12 @@ public function testPreventsComplexExternalEntities()
         }
     }
 
+    public function testDecodeEmptyXml()
+    {
+        $this->setExpectedException('Symfony\Component\Serializer\Exception\UnexpectedValueException', 'Invalid XML data, it can not be empty.');
+        $this->encoder->decode(' ', 'xml');
+    }
+
     protected function getXmlSource()
     {
         return '<?xml version="1.0"?>'."\n".