Sonata Admin: modify validation groups in an admin extension

SonataAdminBundle has a powerful extensions feature which allows you to add or change features of one or more Admin instances.

I needed my extension to change some validation rules, and it turned out that imposing different validation groups was a good way to achieve it. 

$formOptions attribute of Sonata\AdminBundle\Admin\AbstractAdmin class allows for setting validation groups, but I couldn’t find an easy way to modify it in my extension.

getFormBuilder method of AbstractAdmin class is where these $formOptions are added to the form builder:

So, in my admin class I override this method, to add support for extensions:

Now, in your admin extension you can add a method to actually modify $formOptions of the admin class: