What is this about

This PR add support for form attribute to Symfony Form (browser compatibility).

The form attribute allows form elements to override their associated form (which is their nearest ancestor form element by default). This is extremely useful to solve nested form problem and allows form children to be rendered outside form tag while still working as expected.

New "form_attr" FormType option

form_attr

type: bool or string default: false

If set to true on a root form, adds form attribute on every children with their root form id.
This allows you to render form children outside the form tag and avoid nested form problem in some situations while keeping the form working properly.

If set to true on a child, adds form attribute on it with its root form id.
This allows you to render that child outside the form tag and avoid nested form problem in some situations while keeping the form working properly.

If root form has no id (this may happen by create an unnamed form), you can set it to a string identifier to be used at FormView level to link children and root form anyway.

Usage on Root Form Example

Form Type

Enable the feature by setting form_attr to true on the root form.

use Symfony\Component\Form\Extension\Core\Type;

class ListFilterType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder
            ->add('search', Type\SearchType::class)
            ->add('orderBy', Type\ChoiceType::class, [
                'choices' => [
                    // ...
                ],
            ])
            ->add('perPage', Type\ChoiceType::class, [
                'choices' => [
                    // ...
                ],
            ])
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefault('form_attr', true); // <--- Set this to true
    }
}

Twig

The following Twig template works properly even if form children are outside their form tag (browser compatibility).

<div class="header-filters">
    {{ form_errors(form) }}
    {{ form_row(form.search) }} {# has attribute form="list_filter" #}
    {{ form_row(form.orderBy) }} {# has attribute form="list_filter" #}
</div>

<!-- -->
<!-- Some other HTML content, like a table or even another Symfony form -->
<!-- -->

<div class="footer-filters">
    {{ form_row(form.perPage) }} {# has attribute form="list_filter" #}
</div>
{{ form_start(form) }} {# id="list_filter" #}
{{ form_end(form) }}

✅ Every form elements work properly even outside form tag.

Usage on Form Child Example

Enable the feature by setting form_attr to true on selected child.

use Symfony\Component\Form\Extension\Core\Type;

class ListFilterType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder
            ->add('search', Type\SearchType::class)
            ->add('orderBy', Type\ChoiceType::class, [
                'choices' => [
                    // ...
                ],
            ])
            ->add('perPage', Type\ChoiceType::class, [
                'form_attr' => true,  // <--- Set this to true
                'choices' => [
                    // ...
                ],
            ])
    }
}

Twig

The following Twig template works properly even if form.perPage is outside form tag (browser compatibility).

<div class="header-filters">
    {{ form_start(form) }} {# id="list_filter" #}
        {{ form_errors(form) }}
        {{ form_row(form.search) }}
        {{ form_row(form.orderBy) }}
    {{ form_end(form, {'render_rest': false}) }}
</div>

<!-- -->
<!-- Some other HTML content, like a table or even another Symfony form -->
<!-- -->

<div class="footer-filters">
    {{ form_row(form.perPage) }} {# has attribute form="list_filter" #}
</div>

✅ form.perPage element work properly even outside form tag.