Symfony version(s) affected

6.2-beta

Description

The new Psr4DirectoryLoader only supports attribute or annotation type so it will use the AnnotationClassLoader which don’t want to deal with abstract classes:

If AnnotationDirectoryLoader skips them, Psr4DirectoryLoader does not meaning it will crash on abstract classes.

How to reproduce

Configure your routes to use the PSR-4 route loader, eg.

<?php

use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;

return static function (RoutingConfigurator $routes)
{
    $routes->import(['path' => '../src/Controller', 'namespace' => 'App\Controller'], 'annotation');
};

and make one of your controllers extends an abstract one (it does not need to define any method).

Refresh the cache to see the error.

Possible Solution

Psr4DirectoryLoader should skip abstract classes. As it means it will need to create an instance of ReflectionClass it could be useful to make AnnotationClassLoader::load accept these.

Additional Context

Spotted from #48161