Symfony - retreive unmapped fields in nested forms

I'm having a Symfony Type ItemType which is based on an Entity.

class IpQuoteItemsType extends AbstractType
{

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('itemName', TextType::class, [
                'label' => 'Produktname'
            ])
            ...
            ->add('specialDiscount', PercentType::class, [
                'required' => false,
                'label' => 'Sonderrabatt',
                'mapped' => false,
                'attr' => [
                    'placeholder' => 'Sonderrabatt 0,00 %'
                ]
            ])
        ;
    }

    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => IpQuoteItems::class
        ));
    }

}

Which is used as a CollectionType in the final form:

class IpQuotesType extends AbstractType
{

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        ...
        $builder->add('products', CollectionType::class, [
            'entry_type' => IpQuoteItemsType::class,
            'data' => $items
        ]);
    }

}

Under no circumstances I receive the unmapped field specialDiscount. It is still available in the PRE_SUBMIT event of the ItemsType but can't be found anywhere in the final form QuotesType.

Is it possible to sumit unmapped data in nested forms?

You can get unmapped field in your controller like this :

$form->get('nestedEntity')->get('fieldName')->getData()

I don't test with collection but it's work with a customType in OneToOne relation.

Hope this help.