Problem with setting the default value for a ManyToOne relation but only when used in livecomponent with livecollection

[gewait]

I have an entity "Main" which has a OneToMany relation named "children" to the entity "Child".

class Main
{
    #[ORM\OneToMany(targetEntity: Child::class, mappedBy: 'main')]
    private Collection $children;

---

Inside the "Child" there is a ManyToOne relation named "other" to another entity named "Related".

class Child
{
    #[ORM\ManyToOne]
    private ?Related $other = null;

---

When a new child is created I want to set a default value for the relation "other".

I can't do it in the constructor of the entity because I would need the entitymanager for that.

I can't use a factory class, because I want to use this in a livecomponent with a livecollection
and there the creation of the objects is done internally.

So I do it via the data option in the formtype for child:

    src/Form/ChildType.php

    $builder
        ->add('other', EntityType::class, [
            'required' => false,
            'class' => Related::class,
            'choice_label' => 'name',
            'data' => $this->relatedRepository->findOneByName('when_this_is_preselected_then_it_works'),  //set default
        ])

---

This does work in a normal form

but does not work in a live component with a live collection.

---

Since the live collection does all the work internally when creating/adding a new child,
I don't know how or where I can initialize the child.other relation property!

---

Is this the expected behaviour? What am I doing wrong? Can someone help?

---

Reproducer:

live-collection-reproducer-zip.zip

[smnandre]

Do you already made it work with a standard CollectionType ?

[gewait]

No, because some weeks ago I was trying to use a standard CollectionType with the option "allow_add" inside a livecomponent, which did not work (see #1973).

Since then I was under the impression that I have to use the livecollectiontype in livecomponents when using the option "allow_add".

[gewait]

Friendly ping :-) Do you need more information or can you give me a hint on what I can do?

[tsiatka]

same issue here, the data option is not working when using the addCollectionItem

[imbachb]

Had the same issue. In the symfony slack channel someone suggested to override the addCollectionItem Method from LiveCollectionTrait and set the default values accordingly, i.e. change the line where the values are set from

$propertyAccessor->setValue($this->formValues, $propertyPath."[$index]", []);

to

$propertyAccessor->setValue($this->formValues, $propertyPath."[$index]", ['someProperty' => 'defaultValue']);

A bit cumbersome to have to override this function but it does work.
Maybe there is a way to access the form type's data field here so we would only have to define the default values in the Form/SomeType.php class.