How to register new Twig Namespaces from inside a Bundle?

I search for a way to change the configuration of the Symfony twig bundle in order to register additional twig namespaces.

I tripped over prepend extension but this would just solve the problem half way. When I write code like this:

public function prepend(ContainerBuilder $container)
    {
        $bundles = $container->getParameter('kernel.bundles');

        if (isset($bundles['TwigBundle'])) {

            $config = $container->getExtensionConfig('twig')[0];
            $paths = ['/path/to/cms' => 'cms'];

            if (array_key_exists('path', $config)) {
                $paths = array_merge($config['paths'], $paths);
            }

            $config['paths'] = $paths;

            $container->prependExtensionConfig('twig', $config);
        }
    }

This would mean that no other bundle could ever change the twig configuration again:

How to add twig namespaces from inside a bundle without obstructing a way for other bundles to do the same?

Answer

Twig namespaces are an application concern, not a bundle concern.

Registering new namespaces from within the bundle could clash with already defined namespaces by the application that consumes the bundle.

Furthermore, it’s not necessary, because Symfony already auto-crates a namespace for each bundle:

If you install packages/bundles in your application, they may include their own Twig templates (in the Resources/views/ directory of each bundle). To avoid messing with your own templates, Symfony adds bundle templates under an automatic namespace created after the bundle name.

For example, the templates of a bundle called AcmeFooBundle are available under the AcmeFoo namespace. If this bundle includes the template <your-project>/vendor/acmefoo-bundle/Resources/views/user/profile.html.twig, you can refer to it as @AcmeFoo/user/profile.html.twig.

You shouldn’t mess with that configuration. Leave it up to the application developer or the framework to deal with it.