[TwigBridge] Set Form ID on form element, prevent duplicate form element attributes

[ker0x]

Q	A
Branch?	7.1
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	Fix #42075
License	MIT
Doc PR	-

As explained in #42075, when a form is rendered, its ID is displayed in the child div of the <form> element.

This prevents to use the form_attr option on FormType.

Moreover, attributes defined on <form> element are duplicated in the child div

For example, the following form

return $this
    ->createFormBuilder(null, [
        'attr' => [
            'class' => 'foo-bar',
            'data-foo' => 'bar'
        ],
    ])
    ->add('input', TextType::class)
    // ...
;

has the following HTML rendering

<form name="form" method="post" class="foo-bar" data-foo="bar">
    <div id="form" class="foo-bar" data-model="form">
         // ... fields
    </div>
</form>

This PR provides the following fixes

• A new computed variable form_id is available in the view. It is the concatenation of form_ and the ID of the form.
• The <form> element uses the row_attr option instead of attr to display attributes. The row_attr option was never used on the root form and this avoids duplicating attributes.
• The form_attr option now only accepts a boolean value.
  • If set on the root form, each child will have a form attribute with the form_id as value.
  • If set on a child, it will have a form attribute with the form_id as value.

[ker0x]

I just updated the PR with the following changes:

• A new computed variable form_id is available in the view. It is the concatenation of form_ and the ID of the form.
• The <form> element uses the row_attr option instead of attr to display attributes. The row_attr option was never used on the root form and this avoids duplicating attributes.
• The form_attr option now only accepts a boolean value.
  • If set on the root form, each child will have a form attribute with the form_id as value.
  • If set on a child, it will have a form attribute with the form_id as value.

[nicolas-grekas]

Looks like a rebase is needed. Still up to do it?

[ker0x]

@nicolas-grekas PR has been rebase, however unit tests are failing with high and low deps and I don't know why!

[xabbuh]

looks like you need to update the composer.json file of the Twig bridge to make sure that the Form component is not older than 6.3 (in the require-dev and conflict sections)

[nicolas-grekas]

I pushed the fix to the composer.json.
Can you please update the description of the PR? I feel like it's a bit out of sync.

[HeahDude]

Since this issue has been there for a long time already, maybe this should target 6.4 to prevent side effects in the LTS.

[ker0x]

@nicolas-grekas description update 👍

@HeahDude I agree to target 6.4 instead of 5.4

[nicolas-grekas]

target 6.4 instead of 5.4

Would be better I agree. Can you update the target of this PR and rebase on 6.4 please?

[xabbuh]

you will need to update the version constraints similarly to what Nicolas did in 3f3d763#diff-33dca46fccec7efe765aa6cf249fddcdde0d15fa2d01adc052a5e1da01b423c5

[xabbuh]

If we have to make this change here, it seems to me that we need to adapt for custom form types that do not provide the row_attr variable (and that we need to fall back to attr then).