Feature: #98239 - PSR-14 Event to modify form after being built 

Description 

A new PSR-14 event \TYPO3\CMS\Form\Event\AfterFormIsBuiltEvent has been introduced which serves as an improved replacement for the now removed hook $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['ext/form']['afterBuildingFinished'] .

The event provides the $form public property.

Example 

An example event listener could look like the following:

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Form\Event\AfterFormIsBuiltEvent;

class MyEventListener
{
    #[AsEventListener(
        identifier: 'my-extension/after-form-is-built',
    )]
    public function __invoke(AfterFormIsBuiltEvent $event): void
    {
        $event->form->setLabel('foo');
    }
}

Impact 

With the new AfterFormIsBuiltEvent, it is now possible to modify the form definition after it has been built.