Autowire Class with Interface as param in Symfony4 - php

Question

Given a class Publisher like this:
<?php
namespace App\Util\Publisher;
use Symfony\Component\Mercure\Update;
use Symfony\Component\Messenger\MessageBusInterface;
class Publisher
{
protected $topic = null;
protected $bus;
/**
* Publisher constructor.
* #param MessageBusInterface $bus
*/
public function __construct(MessageBusInterface $bus)
{
$this->topic = getenv('TOPIC_MAIN_URL');
$this->bus = $bus;
}
...
}
I would like to autowire it in my controllers like this:
/**
* #Route("/_exp/_exp", name="exp")
*/
public function expAction(Publisher $publisher)
{
...
}
and I added this to my services.yaml:
Symfony\Component\Messenger\MessageBusInterface: ~
App\Util\Publisher\Publisher:
autowire: true
arguments: ['#Symfony\Component\Messenger\MessageBusInterface']
But I get an error:
Cannot instantiate interface Symfony\Component\Messenger\MessageBusInterface
Is that related to the MessageBusInterface or am I doing something wrong with the autowiring. I followed The Symfony docs for autowiring and they seem to be the same?
Thank you!

Answer 1

I believe MessageBusInterface service is already declared by Symfony Messenger component.
Try to remove Symfony\Component\Messenger\MessageBusInterface: ~ from your services.yaml, otherwise you are overriding the default definition.
A note for clarification: MessageBusInterface service does not really exists, it in an alias over the "default bus" service. You can declare other buses, cf documentation