Can anyone tell why these double backslashes are required?

So this is interesting :). Starting in Symfony 3.3, the AppBundle:Article:recentArticles syntax should also work when your controller is a service... as long as your service id matches your class name (like it does in your example). In other words, unless you've registered your service with a non-class id (e.g. my_controller), you should be able to just use one syntax, and Symfony will automatically use your controller as a service if it is registered as one (or instantiate it like normal if it is not).

Given that, what made you create this PR? Were you seeing different behavior or were you confused by something?

Cheers!

I tried helping @marcverney set it up on via Slack, but it did not work for him. @marcverney , can you comment on your setup and on the error message you were getting?

Here it goes. I was trying to embed a controller action in a twig template, this way:

{{ render(controller('AppBundle:Default:completeSignup')) }}

Here is my controller action:

public function completeSignupAction(CategoryRepository $categoryRepository)
{
    // ...
}

And the CategoryRepository service definition

services:
    _defaults:
        autowire: true
        autoconfigure: true
        public: false

    Domain\Model\CategoryRepository:
        factory: ['@doctrine.orm.entity_manager', 'getRepository']
        arguments: ['Domain\Model\Category']    

When I tried to access the page, I got the following error:

An exception has been thrown during the rendering of a template ("Controller "Infrastructure\UI\Symfony\AppBundle\Controller\DefaultController::completeSignupAction()" requires that you provide a value for the "$categoryRepository" argument. Either the argument is nullable and no null value has been provided, no default value has been provided or because there is a non optional argument after this one.").

I then thought that maybe injecting a service in a controller action was not supported for subrequests (as I think that's what render(controller()) does). I searched the docs but couldn't find anything about this, so I asked on the support Slack channel. This is where @greg0ire and others told me to try using the FQCN notation:

{{ render(controller('Infrastructure\\UI\\Symfony\\AppBundle\\Controller\\DefaultController:completeSignupAction')) }}

This worked and my $categoryRepository was correctly injected, so @greg0ire created this PR.

I think this sums it all up.

Ah, and as for my setup, two things:

• I'm trying to follow a ddd-loosely-inspired folder structure, so my AppBundle dir is not a direct child of src, plus not everything is inside AppBundle.
• I'm not very comfortable with the autowiring magic yet, so an error in my service definitions would not come as a surprise.