1.

There's a new way to naming forms with help of getBlockPrefix() method, according to the upgrade info https://github.com/symfony/symfony/blob/2.8/UPGRADE-2.8.md.

The problem is it works only when Forms are instantiated e.g.:

 new MyFormType()

But not by a class name, e.g.:

 'AppBundle/MyFormType'

In the second case, I get the form name like 'my_form' regardless whatever I put into the getBlockPrefix() or getName() methods. But when I pass to the Form Factory an instance of my form type (e.g. new MyFormType() as shown above ), the generated form has the proper block prefix - the one I set, e.g. 'profile' in the example from the upgrade text file:

class UserProfileType extends AbstractType
{
   public function getBlockPrefix()
   {
       return 'profile';
   }
}

2.

It seems that when one tries to create a form in a new way (with a class), it seems there's no any possibility to pass any parameters to its constructor.
Maybe introducing some extra array param to the Form Factory when creating a form from a class would resolve the issue?