I tried adding an override for form_row block in app/Resources/views/form/layout.html.twig:

{% block form_row %}
    MY OVERRIDE START

    <div>
        {{- form_label(form) -}}
        {{- form_widget(form) -}}
        {{- form_errors(form) -}}
    </div>

    MY OVERRIDE END
{% endblock %}

I also added a boolean property to one of the entities (for example Post), and corresponding checkbox field to PostType.

It turns out that form_row block override is not applied to Checkbox form type, and I couldn't find the reason why.

This is not an issue in Symfony nor an issue with version of PHP. I tested on PHP 5.6, PHP 7.1 and both show this behaviour. I also tested on Sylius (with Symfony 3.2) and it works okay there, so I think it is related to something in this demo.

If this is intended, how do I make the checkbox form type use my form_row override?

Thanks!