Symfony 4.1 twig extension - symfony

Question

In Symfony 4.1 I created an twig extension and I tried to use it as an service
twig.extension.active.algos:
class: App\Twig\AppExtension
public: true
tags:
- { name: twig.extension, priority: 1024 }
Unfortunately I receive 'Unable to register extension "App\Twig\AppExtension" as it is already registered'
After many searches I saw that there was a bag in the version of symfony 3.4 but they say the error would have solved. So it's my mistake or just another mistake from symfony team.
My extension is:
use Twig\Extension\AbstractExtension;
use Twig\TwigFilter;
class AppExtension extends \Twig_Extension {
public function getFunctions() {
return array(
new \Twig_SimpleFunction('get_active_algos', array($this, getActiveAlgos')),
);
}
public function getActiveAlgos()
{
return [1,2,3];
}
public function getName()
{
return 'get_active_algos';
}
}

Answer 1

Got bored. Here is a working example of a custom twig function for S4.1. No service configuration required (Update: except for the added $answer argument). I even injected the default entity manager using autowire just because.
namespace App\Twig;
use Doctrine\ORM\EntityManagerInterface;
use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;
class TwigExtension extends AbstractExtension
{
private $em;
private $answer;
public function __construct(EntityManagerInterface $em, int $answer)
{
$this->em = $em;
$this->answer = $answer;
}
public function getFunctions()
{
return array(
new TwigFunction('get_active_algos', [$this, 'getActiveAlgos']),
);
}
public function getActiveAlgos()
{
$dbName = $this->em->getConnection()->getDatabase();
return 'Some Active Algos ' . $dbName . ' ' . $answer;
}
}
Update: Based on the first comment, I updated the example to show injecting a scaler parameter which autowire cannot handle.
# services.yaml
App\Twig\TwigExtension:
$answer: 42
Note that there is still no need to tag the service as an extension. Autoconfig takes care of that by automatically tagging all classes which extend the AbstractExtension.