Feature: #109429 - Introduce PSR-14 ModifyLocalizationHandlerIsAvailableEvent 

See forge#109429

Description 

forge#108049 modernizes the translation workflow in the backend in the Content > Layout and Content > Record module views. Technically, this workflow wizard is backed by localization handlers and finishers.

The PSR-14 event ModifyLocalizationHandlerIsAvailableEvent is now introduced and dispatched in LocalizationHandlerRegistry to allow the availability state of a localization handler to be overridden based on \LocalizationInstructions.

The event has the following properties:

  • public readonly string $identifier: String identifier returned by LocalizationHandlerInterface::getIdentifier() from the handler
  • public readonly string $className: The concrete class name in case a handler has been XCLASSed without changing the identifier
  • public readonly LocalizationInstructions $instructions: The localization instructions passed to the handler's isAvailable() method to define the context
  • public bool $isAvailable: The availability state returned by the handler, which can be altered by a PSR-14 event listener

Example 

EXT:my_extension/Classes/EventListener/DisableManualLocalizationHandlerForCustomTableEventListener.php 
<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\EventListener;

use TYPO3\CMS\Backend\Localization\Event\ModifyLocalizationHandlerIsAvailableEvent;
use TYPO3\CMS\Backend\Localization\Handler\ManualLocalizationHandler;
use TYPO3\CMS\Backend\Localization\LocalizationMode;
use TYPO3\CMS\Core\Attribute\AsEventListener;

final class DisableManualLocalizationHandlerForCustomTableEventListener
{
    #[AsEventListener(identifier: 'myext/disable-manual-localization-handler-custom-table')]
    public function __invoke(
        ModifyLocalizationHandlerIsAvailableEvent $event,
    ): void {
        if ($event->identifier !== 'manual') {
            // Return early if not ManualLocalizationHandler.
            return;
        }
        if ($event->className !== ManualLocalizationHandler::class) {
            // Return early if the manual identifier is provided but
            // a customized (XCLASSed) class is given. This is just an
            // example for that property.
            return;
        }
        if ($event->instructions->mode !== LocalizationMode::TRANSLATE) {
            // Return early if not handling translation
            // (localization) mode.
            return;
        }

        if ($event->instructions->mainRecordType === 'my_custom_table') {
            // Disallow translation/localization for 'my_custom_table'
            // in general with the default core handler.
            $event->isAvailable = false;
        }
    }
}
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Impact 

Custom extensions (public and project-specific) are now able to intercept and determine which handlers are available for localization steps in the translation wizard, based on localization context.