I can’t figure out how to embed a form form a template twig partials in FormType when I want to add another FormType under some condition.

I’am trying to embed a form in symfony 6.
In entity UserSession I have a ManyToOne property

` #[ORMManyToOne(inversedBy: 'userSessions')]
    private ?Employer $employer = null;`

in FormType I need to add a FormType field under a condition

`

$builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
  $form = $event->getForm();
                    $data = $event->getData();
                    
                     if ($data && $data->getFunding()) {
                        $form->add('employer', EmployerType::class);
                    } 
                });`

Then I use a js ajax that fetch a controller method

const bodyContainer = document.body; // Use a common ancestor that is always present
  if (user_register_session_admin_funding) {
    bodyContainer.addEventListener("change", function (event) {
      const target = event.target;
      if (target && target.id === "user_register_session_admin_funding") {
        const fundingId = target.value;
      showEmployerForm(user_register_session_admin_funding, fundingId);
      }
    });
  }
function showEmployerForm(element, fundingId) {
  fetch("/get_funding_details", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Requested-With": "XMLHttpRequest",
    },
    body: JSON.stringify({ fundingId: fundingId }),
  })
    .then((response) => {
      if (!response.ok) {
        throw new Error("Network response was not ok " + response.statusText);
      }
      return response.json();
    })
    .then((data) => {
      const employerFormContainer = document.getElementById("employer-form");
      employerFormContainer.innerHTML = data.form; 
    })
    .catch((error) =>
      console.error("There was a problem with the fetch operation:", error)
    );
}

So what i want is to include the EmloyerType form from a partial twig

#[Route('/get_funding_details', name: 'admin_funding_details')]
    public function fetchBForm(
        Request $request,
        FormFactoryInterface $formFactory,
        FundingRepository $fundingRepo): JsonResponse
    {
        $data = json_decode($request->getContent(), true);
        $fundingId = $data['fundingId'] ?? null;
        $funding = $fundingRepo->findOneBy(['id' => $fundingId]);
        if ($funding) {
            $form = $formFactory->create(UserRegisterSessionAdminType::class);
            $formHtml = $this->renderView('shared/_employer_form.html.twig', [
                'form' => $form->createView(),
            ]);

            return new JsonResponse(['form' => true]);
        }

        return new JsonResponse(['bFormHtml' => '']);
    }

and here the twig partial

{{ form_row(form.employer.firstName) }}
{{ form_row(form.employer.lastName) }}

that gives the following error 500

<!-- Neither the property "employer" nor one of the methods "employer()", "getemployer()"/"isemployer()"/"hasemployer()" or "__call()" exist and have public access in class "SymfonyComponentFormFormView". (500 Internal Server Error) -->

I am aware that my mogic is wrong but I can’t see where. If someone could help me point where

I I follow the doc https://symfony.com/doc/current/form/embedded.htmland and I add my EmployerType without any condition it’s working perfectly.

Thank you for your help 🙂