Fix join when recreation of query from parts.

lib/Doctrine/ORM/QueryBuilder.php

@@ -690,7 +690,13 @@ class QueryBuilder
             );
         }
 
-        $isMultiple = is_array($this->_dqlParts[$dqlPartName]);
+        $isMultiple = is_array($this->_dqlParts[$dqlPartName])
+            && !($dqlPartName == 'join' && !$append);
+
+        // Allow adding any part retrieved from self::getDQLParts().
+        if (is_array($dqlPart) && $dqlPartName != 'join') {
+            $dqlPart = reset($dqlPart);
+        }
 
         // This is introduced for backwards compatibility reasons.
         // TODO: Remove for 3.0

tests/Doctrine/Tests/ORM/QueryBuilderTest.php

@@ -1098,4 +1098,26 @@ class QueryBuilderTest extends \Doctrine\Tests\OrmTestCase
         $this->assertEquals('foo_reg', $query->getCacheRegion());
         $this->assertEquals(Cache::MODE_REFRESH, $query->getCacheMode());
     }
+
+    /**
+     * @group DDC-2253
+     */
+    public function testRebuildsFromParts()
+    {
+        $qb = $this->_em->createQueryBuilder()
+          ->select('u')
+          ->from('Doctrine\Tests\Models\CMS\CmsUser', 'u')
+          ->join('u.article', 'a');
+
+        $dqlParts = $qb->getDQLParts();
+        $dql = $qb->getDQL();
+
+        $qb2 = $this->_em->createQueryBuilder();
+        foreach (array_filter($dqlParts) as $name => $part) {
+            $qb2->add($name, $part);
+        }
+        $dql2 = $qb2->getDQL();
+
+        $this->assertEquals($dql, $dql2);
+    }
 }