Symfony2 FOSUserBundle. Registration using just email.

C:\MyProject\src\MyProject\UserBundle\Form\Type\RegistrationFormType.php

<?php
namespace MyProject\UserBundle\Form\Type;

use FOS\UserBundle\Form\Type\RegistrationFormType as BaseType;
use FOS\UserBundle\Model\UserManager;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use MyProject\UserBundle\Entity\User;

class RegistrationFormType extends BaseType
{
    protected $userManager;
    
    // Add constructor with UserManager
    public function __construct($class, UserManager $userManager)
    {
        parent::__construct($class);
        $this->userManager = $userManager;
    }

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        parent::buildForm($builder, $options);

        $builder
            ->add('firstName')
            ->add('lastName')
            ->remove('username');


        // Add hook on submitted data in order to copy email into username
        $um = $this->userManager;
        $builder->addEventListener(FormEvents::SUBMIT, function (FormEvent $event) use ($um) {
            $user = $event->getData();
            /** @var User $user */
            if ($user) {
                // Set username like email and canonicalize both fields
                $user->setUsername($user->getEmail());
                $um->updateCanonicalFields($user);
            }
        });
    }

    public function getName()
    {
        return 'mp_user_registration';
    }
} 

C:\MyProject\src\MyProject\UserBundle\Resources\config\services.xml

<?xml version="1.0" ?>

<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd">

    <parameters>
        <parameter key="mp_user.registration.form.class">MyProject\UserBundle\Form\Type\RegistrationFormType</parameter>
    </parameters>

    <services>
        <service id="mp_user.registration.form.type" class="%mp_user.registration.form.class%">
            <tag name="form.type" alias="mp_user_registration" />
            <argument>%fos_user.model.user.class%</argument>
            
            <!-- Add UserManager here -->
            <argument type="service" id="fos_user.user_manager" />
        </service>
    </services>

</container>

That's working perfectly for me. Thank you very much. Would you by any chance have the same simple adaptation for the ProfileFormType?

Ok I managed to adapt it ;-)
Hope it will help. Here is the Profile Form Type :

<?php
namespace Acme\UserBundle\Form\Type;

use FOS\UserBundle\Form\Type\ProfileFormType as BaseType;
use FOS\UserBundle\Model\UserManager;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Security\Core\Validator\Constraint\UserPassword as OldUserPassword;
use Symfony\Component\Security\Core\Validator\Constraints\UserPassword;
//use Acme\UserBundle\Entity\User;

class ProfileFormType extends BaseType
{
    protected $userManager;

    // Add constructor with UserManager
    public function __construct($class, UserManager $userManager)
    {
        parent::__construct($class);
        $this->userManager = $userManager;
    }

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        if (class_exists('Symfony\Component\Security\Core\Validator\Constraints\UserPassword')) {
            $constraint = new UserPassword();
        } else {
            // Symfony 2.1 support with the old constraint class
            $constraint = new OldUserPassword();
        }

        $this->buildUserForm($builder, $options);

        $builder
          ->remove('username')
          ->add('current_password', 'password', array(
            'label' => 'form.current_password',
            'translation_domain' => 'FOSUserBundle',
            'mapped' => false,
            'constraints' => $constraint,
        ));

        // Add hook on submitted data in order to copy email into username
        $um = $this->userManager;
        $builder->addEventListener(FormEvents::SUBMIT, function (FormEvent $event) use ($um) {
            $user = $event->getData();
            /** @var User $user */
            if ($user) {
                // Set username like email and canonicalize both fields
                $user->setUsername($user->getEmail());
                $um->updateCanonicalFields($user);
            }
        });
    }

    public function getName()
    {
        return 'acme_user_profile';
    }
}

And the service (mine is in yml) :

    acme_user.profile.form.type:
        class: Acme\UserBundle\Form\Type\ProfileFormType
        arguments:
            - %fos_user.model.user.class%
            - @fos_user.user_manager
        tags:
            - { name: form.type, alias: acme_user_profile }

And of course, adding in config.yml :

fos_user:
    profile:
        form:
            type: acme_user_profile

Thank you again for your example !