symfony: [3.4] Cannot redeclare class Symfony\Bundle\FrameworkBundle\Controller\ControllerNameParser

Q	A
Bug report?	yes
Feature request?	no
BC Break report?	no
RFC?	no
Symfony version	3.4.*
PHP version	5.6.25

We’re currently upgrading a Symfony project to 3.4 on PHP 5.6.25 and my colleague has been having this issue since I’ve added the following block of code to our AppKernel::registerContainerConfiguration method:

        $loader->load(function (ContainerBuilder $container) {
            $container->setParameter('container.autowiring.strict_mode', true);
            $container->setParameter('container.dumper.inline_class_loader', true);
            $container->addObjectResource($this);
        });

It only happened on a second request, and often it had to be a different request, not just the same one (aka refresh didn’t cause it).

He found two ways to make it work :

1. Commenting out the line $container->setParameter('container.dumper.inline_class_loader', true);, or
2. Commenting out the line $kernel->loadClassCache(); in app_dev.php

I personally can’t reproduce the issue on my setup. Any idea what might be happening here ?

Also, it might look like we’re not the only ones : https://stackoverflow.com/questions/47617879/symfony-duplicate-class-definition-in-cache

Thanks for your help. gnutix