How to make form_rest() not display a field with Symfony2?

Another in my opinion less hacky way to do it is this:

{{ form_widget(form._token) }} // render the CSRF Token
{{ form_end(form, {'render_rest': false}) }} // do not render anything else

It's from the official documentation (v3.0) so it's pretty much best practise i guess.

{{ form_rest(form) }} goes at the very end, after rendering each field "manually". If you are using it for the CSRF token you can always render it with:

{# Token CSRF #}
{{ form_widget(form._token) }}

The situation in which you don't want to show some field suggests badly designed form. You could feed some argument(s) into it's __construct to make it conditional (say, include/exclude some fields) or you could just create separate Form classes (which is, in my opinion, a bit overkill).

I had common case few months ago when form differed when user inserted/updated records. It was something like this:

...
public function __construct($isUpdateForm){
    $this->isUpdateForm= $isUpdateForm;
}

public function buildForm(FormBuilder $builder, array $options){
    ....
    $builder->add('some_filed', 'text', ..... );

    if ( $this->isUpdateForm ){
        $builder->add(.....);
    }
    ....
}
....

If for some reasons you're not able to refactor form class you could still display unwanted fields but wrap them into <div> which has CSS display:none attribute. That way "they are still there" (and by all means are processed normally) but are not visible to user.

Hope this helps...

Another option is to explicitly mark the field as rendered:

{% do form.contenu.setRendered %}