How to change the user locale with Symfony 4?

Question

I'm trying to change the user locale with Symfony from a field "locale" in the database. I read the Symfony manual (how to sticky a session for example), but nothing works in my application. Translator still gets the default locale...

I created listeners, subscribers... to dynamically change the locale, but as they are loaded before the firewall listener, I'm unable to change the current value.

I tried to change the priority subscriber, but I lost the user entity. I tried to set locale request in controllers, but I think it's too late.

I don't want to add locales in URLs.

Here my subscriber - listener - code:

public function onKernelRequest(RequestEvent $event)
{
   $user = $this->tokenStorage->getToken()->getUser();
   $request = $event->getRequest();
   $request->setLocale($user->getLocale());
}  

In subscribers, I added:

public static function getSubscribedEvents()
{
   return [
     KernelEvents::REQUEST => [['onKernelRequest', 0]],
   ];
}

Here, my full code:

framework.yml:

default_locale: fr

services.yml:

parameters:
    locale: 'fr'
    app_locales: fr|en|

translation.yml:

framework:
    default_locale: '%locale%'
    translator:
        paths:
            - '%kernel.project_dir%/translations'
        fallbacks:
            - '%locale%'

LocaleSubscriber.php:

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\KernelEvents;

class LocaleSubscriber implements EventSubscriberInterface
{
    private $defaultLocale;

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

    public function onKernelRequest(RequestEvent $event)
    {
        $request = $event->getRequest();
        if (!$request->hasPreviousSession()) {
            return;
        }
        // try to see if the locale has been set as a _locale routing parameter
        if ($locale = $request->attributes->get('_locale')) {
            $request->getSession()->set('_locale', $locale);
        } else {
            // if no explicit locale has been set on this request, use one from the session
            $request->setLocale($request->getSession()->get('_locale', $this->defaultLocale));
        }
    }

    public static function getSubscribedEvents()
    {
        return [
            // must be registered before (i.e. with a higher priority than) the default Locale listener
            KernelEvents::REQUEST => [['onKernelRequest', 20]],
        ];
    }
}

UserLocaleSubscriber.php

// src/EventSubscriber/UserLocaleSubscriber.php
namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Session\SessionInterface;
use Symfony\Component\Security\Http\Event\InteractiveLoginEvent;
use Symfony\Component\Security\Http\SecurityEvents;

/**
 * Stores the locale of the user in the session after the
 * login. This can be used by the LocaleSubscriber afterwards.
 */
class UserLocaleSubscriber implements EventSubscriberInterface
{
    private $session;

    public function __construct(SessionInterface $session)
    {
        $this->session = $session;
    }

    public function onInteractiveLogin(InteractiveLoginEvent $event)
    {
        $user = $event->getAuthenticationToken()->getUser();

        if (null !== $user->getLocale()) {
            $this->session->set('_locale', $user->getLocale());
        }
    }

    public static function getSubscribedEvents()
    {
        return [
            SecurityEvents::INTERACTIVE_LOGIN => 'onInteractiveLogin',
        ];
    }
}

Ex controller annotation:

/**
     * @Route("/user/locale", name="user_locale", requirements={"_locale" = "%app.locales%"})
     * @Route("/{_locale}/user/locale", name="user_locale_locale", requirements={"_locale" = "%app.locales%"})
     */

Answer 1

1. Find the priority of the firewall listener using debug:event kernel.request.
2. Make sure your UserLocaleSubscriber is executed right after the firewall listener.
3. Autowire the TranslatorInterface and manually set the translator locale.

// src/EventSubscriber/UserLocaleSubscriber.php
namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Session\SessionInterface;
use Symfony\Component\Security\Http\Event\InteractiveLoginEvent;
use Symfony\Component\Security\Http\SecurityEvents;
use Symfony\Contracts\Translation\TranslatorInterface;

/**
 * Stores the locale of the user in the session after the
 * login. This can be used by the LocaleSubscriber afterwards.
 */
class UserLocaleSubscriber implements EventSubscriberInterface
{
    private $session;

    private $translator;

    public function __construct(SessionInterface $session, TranslatorInterface $translator)
    {
        $this->session = $session;
        $this->translator = $translator;
    }

    public function onInteractiveLogin(InteractiveLoginEvent $event)
    {
        $user = $event->getAuthenticationToken()->getUser();

        if (null !== $user->getLocale()) {
            $this->translator->setLocale($user->getLocale());
        }
    }

    public static function getSubscribedEvents()
    {
        return [
            SecurityEvents::INTERACTIVE_LOGIN => ['onInteractiveLogin', 7]
        ];
    }
}

Answer 2

It's hard to help without seeing the full code you are using.

Symfony has it's own LocaleListener as well. Make sure your's is executed first.

    /**
     * @return array
     */
    public static function getSubscribedEvents()
    {
        return [
            // must be registered before (i.e. with a higher priority than) the default Locale listener
            KernelEvents::REQUEST => [['onKernelRequest', 20]],
        ];
    }