How to use optional ParamConverter with null default in Route in Symfony Controller

CalculationController.php

<?php

namespace Sps\Bundle\CalculationBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;

class CalculationController extends Controller
{
    /**
     * @Route("/calculation/dormer/calculate/{priceQuoteId}", defaults={"priceQuoteId" = null})
     * @ParamConverter("priceQuoteRequest", isOptional="true", class="SpsPriceQuoteBundle:PriceQuoteRequest", options={"id" = "priceQuoteId"})
     * @Template()
     * @Security("has_role('ROLE_DOMO_CALCULATION_DORMER')")
     */
    public function createAction(PriceQuoteRequest $priceQuoteRequest = null)
    {
    }
}

1. Without defaults in @Route throws: No route found for "GET /calculation/dormer/calculate".
2. Without = null on type hint throws: Unable to guess how to get a Doctrine instance from the request information.
3. Without isOptional on @ParamConverter no error.

At the bottom line 1 and 2 are required to handle null. But 3 doesn't change anything.

What is the actual purpose of isOptional then? Isn't mentioned in the cookbook:

• http://symfony.com/doc/current/bundles/SensioFrameworkExtraBundle/annotations/converters.html

Possibly related:

• https://github.com/sensiolabs/SensioFrameworkExtraBundle/issues/162

Twitter discussion:
https://twitter.com/webdevilopers/status/714143790005620736

👍
I can't see any benefit in this argument.

try this defaults={"priceQuoteId" = ""}

Thanks @mssimi!

In that case I will get an empty string but since type hints I would prefer null since I have to convert a string into a value object afterwards:

class DefaultController extends Controller
{
    public function calculateAction(?string $priceRequestId = null)
    {
        if (null !== $priceRequestId) {
            $id = PriceRequestId::fromString($priceRequestId);
        }
    }

in php7.2 and symfony 4.3 its as simple as

class CalculationController extends Controller
{
    /**
     * @Route("/calculation/dormer/calculate/{priceQuoteId}")
     * @ParamConverter("priceQuoteRequest", class="SpsPriceQuoteBundle:PriceQuoteRequest", options={"id" = "priceQuoteId"})
     * @Template()
     * @Security("has_role('ROLE_DOMO_CALCULATION_DORMER')")
     */
    public function createAction(?PriceQuoteRequest $priceQuoteRequest)
    {
    }

no defaults in Route, no isOptional="true", no = null in function definition. Simply ?PriceQuoteRequest