it's a BC break no? also ref #19492 (comment)

Why would that be a BC break?

Taking into account #19492 (comment) we could of course think about adding a Twig function instead if we do not want to add this method to the FormView class.

the order changes right? before a child named parent might be returned first, whereas now it's always the parent form

alternatively, getting rid of arrayaccess in formview would also do it towards consistent accessors in php as well as twig, but that's a bigger step :)

If you refer to form.parent, this still returns the child form as Twig considers ArrayAccess methods before looking at actually implemented methods. And form.getParent() just is not usable without this change.

alternatively, getting rid of arrayaccess in formview would also do it towards consistent accessors in php as well as twig, but that's a bigger step :)

I don't think that's a good idea DX wise. Being able to use form.child_name is quite convenient.

@xabbuh could we deprecating twig_is_root_form() test func then? I guess it wouldn't useful anymore, replacing it by {% form.getParent() is null %}.

In the other hand, I think the solution should be done in Twig context, because having a getter for a public property seems odd.

What about adding a new Twig function for access to the FormView public properties? Something like this:

public function getPropertyValue($object, string $propertyName)
{
        return $object->$propertyName;
}

for cases where the public property matches the name of the child form (ArrayAccess ambiguity in Twig context):

{# $formView->parent #}
{% if property_value(form, 'parent') is null %}

{# $formView->vars #}
{% if property_value(form, 'vars').attr.class is defined %}

even, other ArrayAccess objects (in userland) with a composition similar to FormView can benefit from it, too.

I have rewritten this solution to add a new parent_form() Twig function instead. I would not deprecate the filter for now. Both the filter and the new function serve their own use cases.

@xabbuh please, create an issue in Symfony Docs to not forget about this. Also, please add some usage examples and if this improves an existing feature add a before/after example. Finally, please check if this fixes something that the current docs say it's not possible to do or buggy. Thanks!

Thank you @xabbuh.

@javiereguiluz it took me some time, but here we go now: symfony/symfony-docs#10999