[FrameworkBundle] set default session.handler alias if handler_id is not provided

Author: Youssef BENHSSAIEN

DependencyInjection/FrameworkExtension.php

@@ -880,6 +880,7 @@ private function registerSessionConfiguration(array $config, ContainerBuilder $c
             // Set the handler class to be null
             $container->getDefinition('session.storage.native')->replaceArgument(1, null);
             $container->getDefinition('session.storage.php_bridge')->replaceArgument(0, null);
+            $container->setAlias('session.handler', 'session.handler.native_file')->setPrivate(true);
         } else {
             $container->setAlias('session.handler', $config['handler_id'])->setPrivate(true);
         }

Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -463,6 +463,7 @@ public function testNullSessionHandler()
         $this->assertTrue($container->hasDefinition('session'), '->registerSessionConfiguration() loads session.xml');
         $this->assertNull($container->getDefinition('session.storage.native')->getArgument(1));
         $this->assertNull($container->getDefinition('session.storage.php_bridge')->getArgument(0));
+        $this->assertEquals('session.handler.native_file', (string) $container->getAlias('session.handler'));
     }
 
     public function testRequest()