added tests on empty values

lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php

@@ -294,10 +294,14 @@ abstract class AbstractHydrator
                     $dqlAlias = $cacheKeyInfo['dqlAlias'];
                     $type     = $cacheKeyInfo['type'];
 
+                    var_dump($dqlAlias);
+                    var_dump($cacheKeyInfo);
+                    echo "\n\n\n";
+
                     // in an inheritance hierarchy the same field could be defined several times.
                     // We overwrite this value so long we don't have a non-null value, that value we keep.
                     // Per definition it cannot be that a field is defined several times and has several values.
-                    if (isset($rowData['data'][$dqlAlias][$fieldName])) {
+                    if (!empty($rowData['data'][$dqlAlias][$fieldName])) {
                         break;
                     }
 

tests/Doctrine/Tests/ORM/Functional/Ticket/DDC6303Test.php

@@ -53,4 +53,49 @@ class DDC6303Test extends \Doctrine\Tests\OrmFunctionalTestCase
             }
         }
      }
+
+     public function testEmptyValuesInJoinedInheritance()
+    {
+        $contractStringEmptyData = '';
+        $contractStringZeroData = 0;
+
+        $contractArrayEmptyData = [];        
+
+        $contractStringEmpty = new DDC6303ContractA();
+        $contractStringEmpty->originalData = $contractStringEmptyData;
+
+        $contractStringZero = new DDC6303ContractA();
+        $contractStringZero->originalData = $contractStringZeroData;
+
+        $contractArrayEmpty = new DDC6303ContractB();
+        $contractArrayEmpty->originalData = $contractArrayEmptyData;
+
+        $this->_em->persist($contractStringZero);
+        $this->_em->persist($contractStringEmpty);
+        $this->_em->persist($contractArrayEmpty);
+
+        $this->_em->flush();
+        
+        // clear entity manager so that $repository->find actually fetches them and uses the hydrator
+        // instead of just returning the existing managed entities
+        $this->_em->clear();
+
+        $repository = $this->_em->getRepository(DDC6303Contract::class); 
+        $dataMap = [
+            $contractStringZero->id => $contractStringZeroData,
+            $contractStringEmpty->id => $contractStringEmptyData,
+            $contractArrayEmpty->id => $contractArrayEmptyData,
+        ];              
+
+        $contracts = $repository->createQueryBuilder('p')
+            ->where('p.id IN(:ids)')
+            ->setParameter('ids', array_keys($dataMap))
+            ->getQuery()->getResult(); 
+
+        
+
+        foreach( $contracts as $contract ){
+            static::assertEquals($contract->originalData, $dataMap[$contract->id], 'contract ' . get_class($contract) . ' not equals to original');
+        }
+     }
 }