The usage of theempty_data option for forms should be documented.empty_data allows to set the data set in the form when it is bound andsetData() wasn't called before.

By default, this isnull or, ifdata_class is set, a new instance of that given class (created by using a no-args constructor).

The option can be overridden by setting a static value (1) or by setting a closure (2), that receives aFormInterface instance as first argument. (2) should be preferred, as it only creates objects on demand.

(1)

public function getDefaultOptions(){    return array(        'empty_data' => new User($this->someDependency)    );}

(2)

public function getDefaultOptions(){    return array(        'empty_data' => function (FormInterface $form) {            return new User($form->get('username')->getData());        }    );}