How to create a Repository as a Service with optional dependancies in Symfony3

Repository.php

<?php

namespace Foo\SomeBundle\Repository;
use Foo\SomeBundle\Dependency;
use Doctrine\ORM\EntityRepository;

class SomeRepository extends EntityRepository implements SomeContract
{
    /**
     * @var Dependency
     */
    private $dependency;

    public function setDependency(Dependency $dependency)
    {
        $this->dependency = $dependency;
    }

    public function findSomething(Directory $directory)
    {
        $dependency = $this->getDependency();
        // Your DQL.
    }

    private function getDependency()
    {
        if (!$this->dependency instanceof Dependency) {
            throw \LogicException('Missing Dependency');
        }

        return $this->dependency;
    }
}

services.yml

services:

    foo.dependency:
        class: Foo\SomeBundle\Dependency

    foo.some_repository:
        class: Foo\SomeBundle\Repository\SomeRepository
        factory: ['@doctrine.orm.entity_manager', getRepository]
        arguments: ['Foo\SomeBundle\Entity\TheEntity']
        calls:
            - [setDependency, ['@foo.dependency']]

    actual.service.that.needs.repository:
        class: Foo\BarBundle\Service
        arguments: ['@foo.some_repository']