From 0eb7d3de5b14efca6a8feceff24ba54cf107734a Mon Sep 17 00:00:00 2001
From: Ilie Pandia <iliep@softconsultant.ro>
Date: Wed, 25 Apr 2018 10:47:58 +0300
Subject: [PATCH] Ref #11957 - diagnosis would be easier if the underling error
 had been exposed.

---
 src/Utility/Xml.php                | 18 ++++++++----------
 tests/TestCase/Utility/XmlTest.php | 13 +++++++++++++
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/Utility/Xml.php b/src/Utility/Xml.php
index eb9bcd69b6f..92816077b91 100644
--- a/src/Utility/Xml.php
+++ b/src/Utility/Xml.php
@@ -157,18 +157,16 @@ protected static function _loadXml($input, $options)
                 $xml = new DOMDocument();
                 $xml->loadXML($input, $flags);
             }
+            return $xml;
         } catch (Exception $e) {
-            $xml = null;
-        }
-        if ($hasDisable && !$options['loadEntities']) {
-            libxml_disable_entity_loader(false);
-        }
-        libxml_use_internal_errors($internalErrors);
-        if ($xml === null) {
-            throw new XmlException('Xml cannot be read.');
+            throw new XmlException('Xml cannot be read. ' . $e->getMessage(), null, $e);
+        } finally {
+            //CakePHP requires PHP 5.6 so we can safely use finally to restore error handling
+            if ($hasDisable && !$options['loadEntities']) {
+                libxml_disable_entity_loader(false);
+            }
+            libxml_use_internal_errors($internalErrors);
         }
-
-        return $xml;
     }
 
     /**
diff --git a/tests/TestCase/Utility/XmlTest.php b/tests/TestCase/Utility/XmlTest.php
index e643c723f89..a86d8e41ccb 100644
--- a/tests/TestCase/Utility/XmlTest.php
+++ b/tests/TestCase/Utility/XmlTest.php
@@ -18,6 +18,7 @@
 use Cake\Core\Configure;
 use Cake\ORM\Entity;
 use Cake\TestSuite\TestCase;
+use Cake\Utility\Exception\XmlException;
 use Cake\Utility\Xml;
 
 /**
@@ -64,6 +65,18 @@ public function tearDown()
         Configure::write('App.encoding', $this->_appEncoding);
     }
 
+    public function testExceptionChainingForInvalidInput(){
+        try {
+            $value = "invalid-xml-input<<";
+            Xml::build($value); //should throw an XmlException
+            $this->assertFalse(true,'This line should not be executed because of exception above.');
+        }catch(XmlException $exception){
+            $cause = $exception->getPrevious();
+            $this->assertNotNull($cause);
+            $this->assertInstanceOf(\Exception::class, $cause );
+        }
+    }
+
     /**
      * testBuild method
      *