Symfony2 overriding bundle HTML form input constraints - forms

Question

I am trying to override FOSUserBundle's max username length. Seems simple enough but I can't manage to do it.
validation.yml
AppBundle\Entity\User:
properties:
username:
- Length: { max: 5, groups: [CustomRegistration] }
config.yml
fos_user:
[...]
user_class: AppBundle\Entity\User
registration:
form:
validation_groups: [CustomRegistration]
Validation itself works fine. If user provides username longer than 5 characters Symfony shows an error that it should not be longer than 5 characters. The problem is that the HTML form input still uses default FOSUserBundle value (255). Form builder seems to totally ignore validation groups. Is there any way I can tell form builder to use my constraints?
I want to mention that HTML validation works when I use XML format but I need to use YAML and it works only by coincidence so I would not like to rely on such quirk.
I also tried to provide custom type in hope that it will change anything but it didn't. Username input still uses maxlength value of 255. For reference:
getDefaultOptions # AppBundle/Form/RegistrationFormType.php
public function getDefaultOptions(array $options)
{
return [
'data_class' => 'AppBundle\Entity\User',
'validation_groups' => ['Default', 'CustomRegistration']
];
}
config.yml
fos_user:
[...]
user_class: AppBundle\Entity\User
registration:
form:
type: appbundle_registration
services.yml
services:
appbundle.registration.form.type:
class: AppBundle\Form\RegistrationFormType
tags:
- { name: form.type, alias: appbundle_registration }

Answer 1

You should add max-length HTML attribute manually to the field.
Validation has no effect on HTML attributes.
buildForm # AppBundle\Form\RegistrationFormType
$builder->add("username", "text", array("attr" => array("maxlength" => "5")));
See: http://symfony.com/doc/current/reference/forms/types/text.html#max-length
If it doesnt solve the issue, take a look at your template. It can be setted there too..