Symfony2 : Embedded form validation is not triggered when editing

Question

Symfony version : 2.8.5

Context: I have an entity Restaurant which has a OneToOne relationship with an entity Coordinates which have several relations with other entities related to Coordinates informations. I my backend I create a form related to Restaurant entity with a custom nested form related to Coordinates.

Nota : I use EasyAdminBundle to generate my backend.

Entities relations scheme :

Restaurant

  1 ________ 1 `Coordinates`
                    * ________ 1 `CoordinatesCountry`
                    1 ________ 1 `CoordinatesFR`
                                      * ________ 1 `CoordinatesFRLane`
                                      * ________ 1 `CoordinatesFRCity`

Backend view :

At this point I try the following scenario :

1. I create a new Restaurant, so I fill the fields related form for the first time. I let the Coordinates nested form blank (empty fields). So after form submission, validation messages are displayed (see image below).

2. I edit the previous form and this time I fill the fields of the Coordinates nested form. After form submission, a new Coordinates entity is hydrated and a relationship is created between Restaurant and Coordinates.

3. Once again I edit the previous form and this time I clear all the fields of the Coordinates nested form. The validation is not triggered and I get the following error :

Expected argument of type "FBN\GuideBundle\Entity\CoordinatesFRCity", "NULL" given

I precise that in CoordinatesFRType (see code below), to trigger the validations message the first time I had to use the option empty_data with a closure (like described in the official doc) to instatiate a new CoordinatesFR instance in case of empty datas (all fields blank). But here, in this article (written by the creator of the Symfony form component), it is explained (see empty_data and datta mappers paragraphs) that the empty_data is only called at object creation. So I think this the reason why my validation does not work anymore in case of edition.

Question : why the validation is not effective anymore when editing my form and clearing all embedded form ?

The code (only what is necessary) :

Restaurant entity

use Symfony\Component\Validator\Constraints as Assert;

class Restaurant
{
    /**
     * @ORM\OneToOne(targetEntity="FBN\GuideBundle\Entity\Coordinates", inversedBy="restaurant", cascade={"persist"})
     * @ORM\JoinColumn(nullable=true, onDelete="SET NULL")
     * @Assert\Valid()
     */
    private $coordinates;
}

Coordinates entity

use Symfony\Component\Validator\Constraints as Assert;

class Coordinates
{
    /**
     * @ORM\ManyToOne(targetEntity="FBN\GuideBundle\Entity\CoordinatesCountry")
     * @ORM\JoinColumn(nullable=false)
     */
    private $coordinatesCountry;

    /**
     * @ORM\OneToOne(targetEntity="FBN\GuideBundle\Entity\CoordinatesFR", inversedBy="coordinates", cascade={"persist"})
     * @ORM\JoinColumn(nullable=true, onDelete="SET NULL")
     * @Assert\Valid()
     */
    private $coordinatesFR;

    /**
     * @ORM\OneToOne(targetEntity="FBN\GuideBundle\Entity\Restaurant", mappedBy="coordinates")
     * @ORM\JoinColumn(nullable=true, onDelete="SET NULL")
     */
    private $restaurant;
}

CoordinatesFR entity

use Symfony\Component\Validator\Constraints as Assert;

class CoordinatesFR extends CoordinatesISO
{
    /**
    * @ORM\ManyToOne(targetEntity="FBN\GuideBundle\Entity\CoordinatesFRLane")
    * @ORM\JoinColumn(nullable=true)
    * @Assert\NotBlank()
    */
   private $coordinatesFRLane;

   /**
    * @ORM\ManyToOne(targetEntity="FBN\GuideBundle\Entity\CoordinatesFRCity")
    * @ORM\JoinColumn(nullable=false)
    * @Assert\NotBlank()
    */
   private $coordinatesFRCity;

    /**
     * @ORM\OneToOne(targetEntity="FBN\GuideBundle\Entity\Coordinates", mappedBy="coordinatesFR")
     * @ORM\JoinColumn(nullable=true, onDelete="SET NULL")
     */
    private $coordinates;
}

Easy Admin config (equivalent to RestaurantType)

easy_admin:
    entities:
        Restaurant:
            class : FBN\GuideBundle\Entity\Restaurant
            form:
                fields:
                    - { property: 'coordinates', type: 'FBN\GuideBundle\Form\CoordinatesType' }

CoordinatesType

class CoordinatesType extends AbstractType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array                $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('CoordinatesCountry', EntityType::class, array(
                'class' => 'FBNGuideBundle:CoordinatesCountry',
                'property' => 'country',
                ))
            ->add('coordinatesFR', CoordinatesFRType::class)
        ;
    }

    /**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'FBN\GuideBundle\Entity\Coordinates',
        ));
    }
}

CoordinatesFRType

class CoordinatesFRType extends AbstractType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array                $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('laneNum', TextType::class)
            ->add('coordinatesFRLane', EntityType::class, array(
                'class' => 'FBNGuideBundle:CoordinatesFRLane',
                'property' => 'lane',
                'placeholder' => 'label.form.empty_value',
                ))
            ->add('laneName', TextType::class)
            ->add('miscellaneous', TextType::class)
            ->add('locality', TextType::class)
            ->add('metro', TextType::class)
            ->add('coordinatesFRCity', EntityType::class, array(
                'class' => 'FBNGuideBundle:CoordinatesFRCity',
                'property' => 'display',
                'query_builder' => function (CoordinatesFRCityRepository $repo) {
                    return $repo->getAscendingSortedCitiesQueryBuilder();
                    },
                'placeholder' => 'label.form.empty_value',
                ))
        ;
    }

    /**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'FBN\GuideBundle\Entity\CoordinatesFR',
            // Ensures that validation error messages will be correctly displayed next to each field 
            // of the corresponding nested form (i.e if submission and CoordinatesFR nested form with all fields empty)
            'empty_data' => function (FormInterface $form) {
                return new CoordFR();
            },
        ));
    }
}