bug symfony#25719 [HttpKernel] Uses cookies to track the requests redirection (sroze)

This PR was merged into the 3.4 branch.

Discussion
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[HttpKernel] Uses cookies to track the requests redirection

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#25698
| License       | MIT
| Doc PR        | ø

In order to track the redirections across requests, we need to have some state. So far, we've been using the session but some users have complained about it (symfony#24774, symfony#24730). The idea is that we don't actually need the session, we can use cookies.

It's a tradeoff: using a cookie would mean that both the redirection and the target page will not be cachable (because of the Set-Cookie to set the sf_redirect and the one to clear it).

As it's only on dev, it seems fair to say that having no cache (because of `Set-Cookie`s) is a better side effect than starting the session.

Commits
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83f2579 Uses cookies to track the requests redirection

Author: fabpot

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

@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\HttpKernel\DataCollector;
 
+use Symfony\Component\HttpFoundation\Cookie;
 use Symfony\Component\HttpFoundation\ParameterBag;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -128,21 +129,24 @@ public function collect(Request $request, Response $response, \Exception $except
             unset($this->controllers[$request]);
         }
 
-        if (null !== $session) {
-            if ($request->attributes->has('_redirected')) {
-                $this->data['redirect'] = $session->remove('sf_redirect');
-            }
+        if ($request->attributes->has('_redirected') && $redirectCookie = $request->cookies->get('sf_redirect')) {
+            $this->data['redirect'] = json_decode($redirectCookie, true);
+
+            $response->headers->clearCookie('sf_redirect');
+        }
 
-            if ($response->isRedirect()) {
-                $session->set('sf_redirect', array(
+        if ($response->isRedirect()) {
+            $response->headers->setCookie(new Cookie(
+                'sf_redirect',
+                json_encode(array(
                     'token' => $response->headers->get('x-debug-token'),
                     'route' => $request->attributes->get('_route', 'n/a'),
                     'method' => $request->getMethod(),
                     'controller' => $this->parseController($request->attributes->get('_controller')),
                     'status_code' => $statusCode,
                     'status_text' => Response::$statusTexts[(int) $statusCode],
-                ));
-            }
+                ))
+            ));
         }
 
         $this->data['identifier'] = $this->data['route'] ?: (is_array($this->data['controller']) ? $this->data['controller']['class'].'::'.$this->data['controller']['method'].'()' : $this->data['controller']);
@@ -312,11 +316,11 @@ public function onKernelController(FilterControllerEvent $event)
 
     public function onKernelResponse(FilterResponseEvent $event)
     {
-        if (!$event->isMasterRequest() || !$event->getRequest()->hasSession()) {
+        if (!$event->isMasterRequest()) {
             return;
         }
 
-        if ($event->getRequest()->getSession()->has('sf_redirect')) {
+        if ($event->getRequest()->cookies->has('sf_redirect')) {
             $event->getRequest()->attributes->set('_redirected', true);
         }
     }