Symfony RequestStack and RequestRegistry

RequestRegistry.php

<?php

namespace Symfony\Component\HttpFoundation;

/**
 * Registry for Requests.
 *
 * Facade for RequestStack that prevents modification of the stack,
 * so that users don't accidentily push()/pop() from the stack and
 * mess up the request cycle.
 */
class RequestRegistry
{
    private $stack;

    public function __construct(RequestStack $stack)
    {
        $this->stack = $stack;
    }

    /**
     * @return Request
     */
    public function getCurrentRequest()
    {
        return $this->stack->getCurrentRequest();
    }

    /**
     * @return Request
     */
    public function getMasterRequest()
    {
        return $this->stack->getMasterRequest();
    }
}

RequestStack.php

<?php

namespace Symfony\Component\HttpFoundation;

/**
 * Request stack that controls the lifecycle of requests.
 *
 * Notifies services of changes in the stack.
 */
class RequestStack
{
    /**
     * @var Request
     */
    private $masterRequest;

    /**
     * @var Request[]
     */
    private $requests = array();

    private $eventDispatcher;

    public function __construct(EventDispatcherInterface $eventDispatcher)
    {
        $this->eventDispatcher = $eventDispatcher;
    }

    public function push(Request $request)
    {
        if (HttpKernelInterface::MASTER_REQUEST === $request->getType()) {
            $this->masterRequest = $request;
        }

        $this->requests[] = $request;
        $this->dispatch('request.enter_scope', new RequestEnterScopeEvent($request));
    }

    /**
     * Pop the current request from the stack.
     *
     * This operation lets the current request go out of scope.
     *
     * @return Request
     */
    public function pop()
    {
        $previousRequest = array_pop($this->requests);

        $this->dispatch('request.leave_scope',
            new RequestLeaveScopeEvent(
                $previousRequest,
                $this->getCurrentRequest()
            )
        );

        return $request;
    }

    /**
     * @return Request
     */
    public function getCurrentRequest()
    {
        return end($this->requests);
    }

    /**
     * @return Request
     */
    public function getMasterRequest()
    {
        return $this->masterRequest;
    }
}

RequestStackAwareHttpKernel.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\DependencyInjection;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;
use Symfony\Component\HttpKernel\HttpKernel;
use Symfony\Component\HttpKernel\Controller\ControllerResolverInterface;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\DependencyInjection\Scope;

/**
 * Adds a managed request scope.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 * @author Johannes M. Schmitt <schmittjoh@gmail.com>
 */
class RequestStackAwareHttpKernel extends HttpKernel
{
    protected $stack;

    /**
     * Constructor.
     *
     * @param EventDispatcherInterface    $dispatcher         An EventDispatcherInterface instance
     * @param ControllerResolverInterface $controllerResolver A ControllerResolverInterface instance
     */
    public function __construct(EventDispatcherInterface $dispatcher, ControllerResolverInterface $controllerResolver, RequestStack $stack)
    {
        parent::__construct($dispatcher, $controllerResolver);

        $this->stack = $stack;
    }

    /**
     * {@inheritdoc}
     */
    public function handle(Request $request, $type = HttpKernelInterface::MASTER_REQUEST, $catch = true)
    {
        $request->headers->set('X-Php-Ob-Level', ob_get_level());

        $this->stack->push($request);

        try {
            $response = parent::handle($request, $type, $catch);
        } catch (\Exception $e) {
            $this->stack->pop();

            throw $e;
        }

        $this->stack->pop();

        return $response;
    }
}

RouterListener.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\EventListener;

use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\RequestContextAwareInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * Initializes the locale based on the current request.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class LocaleListener implements EventSubscriberInterface
{
    private $router;
    private $defaultLocale;

    public function __construct($defaultLocale = 'en', RequestContextAwareInterface $router = null)
    {
        $this->defaultLocale = $defaultLocale;
        $this->router = $router;
    }

    public function onRequestLeaveScope(RequestLeaveScopeEvent $event)
    {
        $request = $event->getCurrentRequest();

        if (null === $request) {
            return;
        }

        if ($locale = $request->attributes->get('_locale')) {
            $request->setLocale($locale);
        }

        if (null !== $this->router) {
            $this->router->getContext()->setParameter('_locale', $request->getLocale());
        }
    }

    public function onRequestEnterScope(RequestEnterScopeEvent $event)
    {
        $request = $event->getRequest();
        $request->setDefaultLocale($this->defaultLocale);

        $this->setRequest($request);
    }

    public static function getSubscribedEvents()
    {
        return array(
            // TODO Adjust
        );
    }
}

@Baachi Why extend SplStack? it has a HUGE api where here we only need push()/pop(). This would create a big unnecessary API

@beberlei I agree with you

Please review symfony/symfony#7707 which is the pull request for this idea.