how to make form ignore password fields if blank (symfony2 forms)

On your entity setter for the password property make it like this:

/**
 * Set password
 *
 * @param string $password
 * @return User
 */
public function setPassword($password)
{
    if (!is_null($password)) {
        $this->password = $password;
    }

    return $this;
}

The trick is to check if the parameter being passed is empty and only setting if it's not.

For someone else's reference, I worked this one out this way.

My formType:

public function buildForm(FormBuilder $builder, array $options)
{   

    $builder
        ->add('username', 'text', array('label' => 'Servernamn '))            
        ->add('plainPassword', 'repeated', array('type' => 'password', 'first_name' => 'Lösenord för server ', 'second_name' => 'Upprepa lösenord för server',));

    $builder-> addValidator(new CallbackValidator(function(FormInterface $form){
      $username = $form->get('username')->getData();
        if (empty($username)) {
          $form['username']->addError(new FormError("Du måste ange ett namn för servern"));
        }
    }));

}

My updateAction:

public function updateServerAction($id)
{
    $em = $this->getDoctrine()->getEntityManager();

    $entity = $em->getRepository('BizTVUserBundle:User')->find($id);

    if (!$entity) {
        throw $this->createNotFoundException('Unable to find Container entity.');
    }

    $originalPassword = $entity->getPassword(); 

    $editForm   = $this->createForm(new editServerType(), $entity);

    $request = $this->getRequest();

    $editForm->bindRequest($request);

    if ($editForm->isValid()) {

        $plainPassword = $editForm->get('plainPassword')->getData();
        if (!empty($plainPassword))  {  
            //encode the password   
            $encoder = $this->container->get('security.encoder_factory')->getEncoder($entity); //get encoder for hashing pwd later
            $tempPassword = $encoder->encodePassword($entity->getPassword(), $entity->getSalt()); 
            $entity->setPassword($tempPassword);                
        }
        else {
            $entity->setPassword($originalPassword);
        }

        $em->persist($entity);
        $em->flush();

        return $this->redirect($this->generateUrl('Server'));
    }

Thus updating my users password should it be set, otherwise keep the original password.

What I did was to leave the UserType as is and only remove the password field in the controller:

/**
 * @Route("/users/edit/{username}", name="user_edit")
 */
public function editAction(Request $request, User $user)
{
    $form = $this->createForm(UserType::class, $user);

    // Remove the password field when editing the user
    // Otherwise it must be entered each time the user is edited
    // We can change the password via a special edit-user-password page
    $form->remove('password');

    $form->handleRequest($request);

    if ($form->isValid()) {
        // ...
    }
}

This way you can have a single UserType, reusable in the editAction and the newAction.

Be sure to add the line $form->remove('password'); before $form->handleRequest($request);.

If you need add required option to $options array. Example:

public function buildForm(FormBuilder $builder, array $options)
{   

    $builder
        ->add('username', 'text', array('label' => 'Servernamn '))            
        ->add('plainPassword', 'repeated', array(
                  'type' => 'password', 
                  'first_name' => 'password', 
                  'second_name' => 'repeat_password', 
                  'required' => false,
            ));
}