Symfony 3.3 Dependency Injection changes - php

Question

In Synfony 3.3, the new best practice for DI
is to use normal constructor dependency injection (or "action"
injection in controllers) instead of fetching public services via
$this->get() (though that does still work)
as seen in offical documentation
So no need to specify services as we can type hint them in class controllers :
class InvoiceMailer
{
private $generator;
public function __construct(InvoiceGenerator $generator)
{
$this->generator = $generator
}
// ...
}
This seems to work well, but what if I extends a class and add more parameters in my constructors ???
use Symfony\Component\HttpKernel\Exception\HttpException;
class MyClass extends HttpException
{
private $generator;
public function __construct(InvoiceGenerator $generator, \Exception $previous = null, array $headers = [], $code = 0)
{
$this->generator = $generator;
$statusCode = $generator->getStatusCode();
$message = $generator->getTitle();
parent::__construct($statusCode, $message, $previous, $headers, $code);
}
// ...
}
Now I get a circular reference error :
[Symfony\Component\DependencyInjection\Exception\ServiceCircularReferenceException]
Circular reference detected for service "AppBundle\Service\MyClass", path: "AppBundle\Service\MyClass -> AppBundle\Service\MyClass".
So, what is the best practice in this case ??
Thanks.

Answer 1

For that case you might have to define the service explicitly as \Exception $previous argument in fact is parent class of MyClass (through HttpException) so the autowiring method try to inject/create an instance of MyClass again on this argument, result: "Circular Reference".
This is an abstraction of what happens to you:
namespace App\Foo;
class MyClass extends \Exception
{
public function __construct(\Exception $previous = null)
{
}
}
Same error, so you can to solve it passing a null value to this argument:
# service.yml
services:
# ...
App\Foo\MyClass:
$previous: ~
or changing its definition manually in a compiler pass or DI extension.