Form "PercentType" parameter "scale" inconsistency with "NumberType"

[emmanuelballery]

Description

Parameter scale of PercentType is a bit confusing when you know how it works for the NumberType one:

• NumberType will round the submitted value, meaning the model will be rounded too; What's saved and what's shown in the view is identical.
• PercentType will round the view only, but will save the model with all the decimals sent.

Example

Consider this form:

$form = $this
    ->createFormBuilder()
    ->add('number', NumberType::class, ['scale' => 2])
    ->add('percent', PercentType::class, ['type' => 'integer', 'scale' => 2])
    ->getForm();

Then submit values with more decimals than the scale is set to and dump the model:

Something like:

$form->submit(['number' => 1.234, 'percent' => 1.234]);
dump($form->getData());

The NumberType will actually round the model. The PercentType one will ignore this scale and keep every decimals in the model.

But the view will then show:

Leading to something strange, in my opinion.

Having the same behaviour for both would be great, or changing the name of this parameter in PercentType to make this difference clearer like view_scale for example.

Thanks!

[VincentLanglet]

Is there a reason for keeping the different behaviour ?
I expect the value to be rounded too for the PercentType.

[emmanuelballery]

I wanted to add that the scale parameter is required in PercentType (in PercentToLocalizedStringTransformer you will see that $scale is set to 0 if null is provided). But in NumberType, it's fine to ignore the scale and NumberToLocalizedStringTransformer will ignore the rounding process). There is no reason to require a scale, sometimes it's just not necessary.

[VincentLanglet]

It doesn't seem clear to me in the documentation that the different rounding behaviour are expected.
https://symfony.com/doc/current/reference/forms/types/percent.html#scale
https://symfony.com/doc/current/reference/forms/types/number.html#scale

[VincentLanglet]

@emmanuelballery I started a PR here: #35729