How to add extra bag to symfony session

Question

I want to add an extra bag to symfony session.

I do that in compiler pass:

public function process(ContainerBuilder $container)
{   
    $bag = new AttributeBag("my_session_attributes");

    $container->getDefinition("session")
        ->addMethodCall("registerBag", [$bag]);
}

But i get an exception with message:

Unable to dump a service container if a parameter is an object or a resource.

Here is the trace stack:

1. in XmlDumper.php line 379
2. at XmlDumper::phpToXml(object(AttributeBag)) in XmlDumper.php line 328
3. at XmlDumper->convertParameters(array(object(AttributeBag)), 'argument', object(DOMElement)) in XmlDumper.php line 94
4. at XmlDumper->addMethodCalls(array(array('registerBag', array(object(AttributeBag)))), object(DOMElement)) in XmlDumper.php line 183
5. at XmlDumper->addService(object(Definition), 'session', object(DOMElement)) in XmlDumper.php line 272
6. at XmlDumper->addServices(object(DOMElement)) in XmlDumper.php line 52
7. at XmlDumper->dump() in ContainerBuilderDebugDumpPass.php line 34
8. at ContainerBuilderDebugDumpPass->process(object(ContainerBuilder)) in Compiler.php line 104
9. at Compiler->compile(object(ContainerBuilder)) in ContainerBuilder.php line 598
10. at ContainerBuilder->compile() in Kernel.php line 514
11. at Kernel->initializeContainer() in Kernel.php line 133
12. at Kernel->boot() in Kernel.php line 182
13. at Kernel->handle(object(Request)) in app_dev.php line 29

How should I add new bag if I can't pass object arguments in service definitions?

Answer 1

Ok, just after posting the question I had an idea which I consider a workaround but it works.

The AttributeBag has to be registered as service too:

public function process(ContainerBuilder $container)
{   
    $bagDefinition = new Definition();
    $bagDefinition->setClass(AttributeBag::class);
    $bagDefinition->addArgument("my_session_attributes");
    $bagDefinition->addMethodCall("setName", ["my_session_attributes"]);
    $bagDefinition->setPublic(false);
    $container->setDefinition("my_session_attributes_service", $bagDefinition);

    $container->getDefinition("session")
        ->addMethodCall("registerBag", [new Reference("my_session_attributes_service")]);
}

Answer 2

This matter is not clear in doc, your example helped a bit but I think there is a more clean way to add a bag to symfony session, here is what I did (symfony 4+)

Add a bag class, for instance you can extends the AttributeBag one

namespace App\Tracking;
use Symfony\Component\HttpFoundation\Session\Attribute\AttributeBag;    

class TrackingBag extends AttributeBag
{
    public function __construct(string $storageKey = 'trackings')
    {
        parent::__construct($storageKey);
        $this->setName($storageKey);
    }
}

Then add a CompilerPass

public function process(ContainerBuilder $container)
{
    $container->getDefinition("session")->addMethodCall(
        "registerBag",
        [new Reference('App\\Tracking\\TrackingBag')]
    );
}

Then you can use it like that in twig

{{ app.session.bag('trackings').all }}

I still believe there is cleaner way but this was the only one which worked for me.