[HttpKernel] Fix a regression in the RequestDataCollector

src/Symfony/Component/HttpKernel/DataCollector/RequestDataCollector.php

@@ -374,7 +374,7 @@ class RequestDataCollector extends DataCollector implements EventSubscriberInter
             );
         }
 
-        return (string) $controller ?: 'n/a';
+        return is_string($controller) ? $controller : 'n/a';
     }
 
     private function getCookieHeader($name, $value, $expires, $path, $domain, $secure, $httponly)

src/Symfony/Component/HttpKernel/Tests/DataCollector/RequestDataCollectorTest.php

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\HttpKernel\Tests\DataCollector;
 
+use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Session\Session;
 use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
 use Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface;
@@ -182,6 +183,17 @@ class RequestDataCollectorTest extends \PHPUnit_Framework_TestCase
         );
     }
 
+    public function testItIgnoresInvalidCallables()
+    {
+        $request = $this->createRequestWithSession();
+        $response = new RedirectResponse('/');
+
+        $c = new RequestDataCollector();
+        $c->collect($request, $response);
+
+        $this->assertSame('n/a', $c->getController());
+    }
+
     protected function createRequest()
     {
         $request = Request::create('http://test.com/foo?bar=baz');
@@ -194,6 +206,16 @@ class RequestDataCollectorTest extends \PHPUnit_Framework_TestCase
         return $request;
     }
 
+    private function createRequestWithSession()
+    {
+        $request = $this->createRequest();
+        $request->attributes->set('_controller', 'Foo::bar');
+        $request->setSession(new Session(new MockArraySessionStorage()));
+        $request->getSession()->start();
+
+        return $request;
+    }
+
     protected function createResponse()
     {
         $response = new Response();