Feature/discussion: generic approach to add controllers from FormType classes

[zmitic]

I find Stimulus great to improve forms. There is just one problem that I may not know how to solve so here comes an example:

My root form has controller unload that will ask user to confirm turbo:visit if FormData has been changed. And it works but the code is a problem:

My theme.twig

{% use 'bootstrap_4_layout.html.twig' %}

 {% block attributes %}

     {%- if form is rootform and (not unload_rendered is defined) -%}
         {{ stimulus_controller('unload') }}
         {{ stimulus_action({
             'unload':
             {
                 'turbo:submit-start': 'leavingPage',
                 'change': 'onChange',
                 'turbo:click@window->unload': 'leavingPage',
                 'turbo:before-visit@window': 'leavingPage',
                 'beforeunload@window': 'leavingPage',
             }
         }) }}

     {%- endif %}

     {{- parent() -}}

 {% endblock %}

{%- block widget_container_attributes -%}

    {% if form is rootform and (not unload_rendered is defined) %}
        {% set unload_rendered = true %}
    {% endif %}

    {{- parent() -}}
{%- endblock widget_container_attributes -%}

unload_rendered is used to prevent duplicate controllers.

The problem here is that if I wanted to use bootstrap_4_horizontal_layout.html.twig instead, I would need to create another file (am I wrong about this?).

It becomes an even bigger problem for reusable bundles or FormExtensions that want to attach their own controllers (like having 2-3 of them, each with its own logic).

It would have been much easier if the same can be provided via PHP.

---

The idea

FormView::vars could get another array property called stimulus_controllers.

Then in Twig, template block widget_attributes would read and render them unescaped (this is the biggest issue I had with attributes approach).

End use

$builder->add('firstName', TextType::class, [
    'controller' => 'my-validation'
]);

which would render

<input data-controller="my-validation" ... />

If there was a registered FormExtension for TextType that add its own always-added controller:

<input data-controller="my-validation always-added" ... />

---

FormView example:

public function buildView(FormView $view, FormInterface $form, array $options): void
{
    $view->vars['stimulus_controllers']['my-controller'] = ['onVisit' => 'turbo:visit@window'];
}

---

WDYT? Does the idea even make sense?