Symfony 5 - DataTransformer with Form Validation Constraint - symfony

Question

I build a FormType in Symfony5 and make use of DataTransformer on 2 fields :
compagnie_princ
compagnie_sec.
DataTransformer basically takes an object ID and renders It to a label.
DataTransformer works fine, when Form is initially rendered on browser, see below capture:
Problem is after validation callbacks are executed, If an error occured, It fails to transform my Id back to a text value.
Code samples (most important parts) :
AccordCommercialFormType.php
public function buildForm(FormBuilderInterface $builder, array $options): void
{
$builder
->add('compagnie_princ', TextType::class,
[
'label' => 'forms.parameter.accord.compagnie_princ',
]
)
->add('compagnie_sec', TextType::class,
[
'label' => 'forms.parameter.accord.compagnie_sec',
]
);
/** ... **/
$builder>addEventListener(
FormEvents::PRE_SET_DATA,
[$this, 'onPreSetData']
)
->addEventListener(
FormEvents::PRE_SUBMIT,
[$this, 'onPreSubmit']
);
$builder->get('compagnie_princ')->addModelTransformer($this->transformer);
$builder->get('compagnie_sec')->addModelTransformer($this->transformer);
}
Events are captured on preSubmit to fetch ID, because fields 'compagnie_princ' and 'compagnie_sec' are autocompleted with AJAX, populating hidden inputs. My guess is something is going wrong on that part.
public function onPreSetData(FormEvent $event): void
{
$form = $event->getForm();
$form->add('compagnie_princ_id', HiddenType::class,
['mapped' => false,
'attr' => ['class' => 'hidden-field'],
'data' => $event->getData()->getCompagniePrinc() ? $event->getData()->getCompagniePrinc()->getId() : null
]
);
$form->add('compagnie_sec_id', HiddenType::class,
['mapped' => false,
'attr' => ['class' => 'hidden-field'],
'data' => $event->getData()->getCompagnieSec() ? $event->getData()->getCompagnieSec()->getId() : null,
]
);
}
public function onPreSubmit(FormEvent $event): void
{
$data = $event->getData();
$data['compagnie_princ'] = (int)$data['compagnie_princ_id'];
$data['compagnie_sec'] = (int)$data['compagnie_sec_id'];
$event->setData($data);
}
CompagnieToIdTransformer.php
class CompagnieToIdTransformer implements DataTransformerInterface
{
public function __construct(private EntityManagerInterface $em){
}
public function transform($compagnie)
{
if (null === $compagnie) {
return '';
}
return $compagnie->getCodeIata();
}
public function reverseTransform($compagnieId):?Compagnie
{
if (!$compagnieId) {
return null;
}
$compagnie = $this->em
->getRepository(Compagnie::class)
->find($compagnieId)
;
if (null === $compagnie) {
throw new TransformationFailedException(sprintf(
'A company with number "%s" does not exist!',
$compagnieId
));
}
return $compagnie;
}
}