Symfony: Unable to load Twig Extension runtime

Question

I was following this guide to add a custom Twig extension to Symfony 4 project.

My App\Twig\AppExtension is as follow:

<?php

namespace App\Twig;

use Twig\Extension\AbstractExtension;
use Twig\TwigFunction;

class AppExtension extends AbstractExtension
{
    public function getFunctions()
    {
        return [
            new TwigFunction('getController', [AppRuntime::class, 'getController'])
        ];
    }
}

And My App\Twig\AppRuntime:

<?php

namespace App\Twig;

use Symfony\Component\HttpFoundation\RequestStack;

class AppRuntime
{
    private $request;

    public function __construct(RequestStack $requestStack)
    {
        $this->request = $requestStack->getCurrentRequest();
    }

    public function getController()
    {
        return $this->request->get('_controller');
    }
}

But If I try to use getController() function in a template, I'm getting this exception: Unable to load the "App\Twig\AppRuntime" runtime.

The following line from Twig template produces this error:

echo twig_escape_filter($this->env, $this->env->getRuntime('App\Twig\AppRuntime')->getController(), "html", null, true);

php bin/console debug:container shows App\Twig\AppRuntime as a correct service. I've also tried setting App\Twig\AppRuntime as a public service, but without luck.

What can be the problem here?

What is your version of Twig? Support for what you are doing was added in Twig 1.26. — Jason Roman
Have you tagged the App\Twig\AppRuntime service with twig.runtime? — vstm
Yes It was twig.runtime tag. It is not documented anywhere... — spajak
In fact it is documented in the guide you linked but with very unnoticeable printing at the very end of the instruction. I had exactly the same problem when was doing my Twig extension first time but after some time I noticed it finally :) — Jacek Dziurdzikowski

Jacek Dziurdzikowski Jacek Dziurdzikowski · Accepted Answer · 2018-06-14T08:19:01

Most probably you forgot to tag your twig extension service.

Here you got explanation how to do it in the first example: https://symfony.com/doc/current/service_container/tags.html

Symfony: Unable to load Twig Extension runtime

1 Answers