Feature: #107568 - PSR-14 event before renderable is validated

Description

A new PSR-14 event BeforeRenderableIsValidatedEvent has been introduced. It serves as an improved replacement for the now removed hook $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['ext/form']['afterSubmit'].

The new event is dispatched right before a renderable is validated.

The event provides the following public properties:

$value: The submitted value of the renderable.
$formRuntime: The form runtime object (read-only).
$renderable: The renderable (read-only).
$request: The current request (read-only).

Example

An example event listener could look like this:

Example event listener class

use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Core\Error\Error;
use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Core\Localization\TranslationService;
use TYPO3\CMS\Form\Event\BeforeRenderableIsValidatedEvent;

final class BeforeRenderableIsValidatedEventListener
{
    #[AsEventListener('my-extension/before-renderable-is-validated')]
    public function __invoke(BeforeRenderableIsValidatedEvent $event): void
    {
        $renderable = $event->renderable;
        if ($renderable->getType() !== 'AdvancedPassword') {
            return;
        }

        $elementValue = $event->value;
        if ($elementValue['password'] !== $elementValue['confirmation']) {
            $processingRule = $renderable
                ->getRootForm()
                ->getProcessingRule($renderable->getIdentifier());

            $processingRule->getProcessingMessages()->addError(
                GeneralUtility::makeInstance(
                    Error::class,
                    GeneralUtility::makeInstance(TranslationService::class)->translate('validation.error.1556283177', null, 'EXT:form/Resources/Private/Language/locallang.xlf'),
                    1556283177
                )
            );
        }

        $event->value = $elementValue['password'];
    }
}

Impact

With the new BeforeRenderableIsValidatedEvent, it is now possible to modify or validate the value of a renderable element before TYPO3 Core performs its built-in validation logic. This allows extensions to inject custom validation rules or preprocessing steps before standard validation runs.