Symfony3 add locale in deeplink - symfony

Question

I create a new site in symfony3 following the getting started section in the official symfony documentation in https://symfony.com/doc/current/setup.html
Everything is working ok.. if I put mydomain.com as the URL, the framework add /en or the correct local.
My question is if there is a way that if the user do a deeplink to mydomain.com/blog the framework found that the local is not present so it can add and transform the url to mydomain.com/en/blog
I'm not adding the code as it is the default one. Let me know if you need it.

Answer 1

There are multiple ways to do this. Probably the easiest is to have an EventSubscriber or -Listener that catches request without a locale and then handles adding that information. Since you based your project on the demo application you might want to look at their solution: https://github.com/symfony/demo/blob/master/src/EventSubscriber/RedirectToPreferredLocaleSubscriber.php
The steps to perform in your event handler are roughly these:
Listen to kernel.request event
Return early based on some criteria, e.g. homepage, a cookie with the language is set, or something else
Detect the language either by getting the default locale or determining from your available locales and the browser header which language fits best (see: https://github.com/willdurand/Negotiation#language-negotiation)
Redirect, add the locale as attribute to request, write the currently set language to a cookie, or whatever else you need to do to change the route

Answer 2

Thanks to #dbrumann I get to this solution... For sure it can be improve to use less code but it just did the trick.
I updated the onKernelRequest method in RedirectToPreferredLocaleSubscriber class
public function onKernelRequest(GetResponseEvent $event): void
{
$request = $event->getRequest();
$path = explode('/',$request->getPathInfo());
$hasLocale = false;
foreach ($this->locales as $key => $l) {
if($l == $path[1]){
$hasLocale = true;
}
}
if(!$hasLocale){
// Ignore sub-requests and all URLs but the homepage
if (!$event->isMasterRequest() || '/' !== $request->getPathInfo()) {
$preferredLanguage = $request->getPreferredLanguage($this->locales);
if ($preferredLanguage !== $this->defaultLocale) {
$url = "";
foreach ($path as $key => $p) {
if($key > 0){
$url .= "/" . $p;
}
}
//print_r('/' . $preferredLanguage . $url);exit;
$response = new RedirectResponse('/' . $preferredLanguage . $url);
$event->setResponse($response);
}
}
else{
// Ignore requests from referrers with the same HTTP host in order to prevent
// changing language for users who possibly already selected it for this application.
if (0 === mb_stripos($request->headers->get('referer'), $request->getSchemeAndHttpHost())) {
return;
}
$preferredLanguage = $request->getPreferredLanguage($this->locales);
if ($preferredLanguage !== $this->defaultLocale) {
$response = new RedirectResponse($this->urlGenerator->generate('homepage', ['_locale' => $preferredLanguage]));
$event->setResponse($response);
}
}
}
}