Breaking: #96726 - RequestHandler functionality of Extbase removed

See forge#96726

Description

Extbase - TYPO3's MVC system has had a way to define "RequestHandlers", which were primarily introduced back in 2010 to distinguish between Frontend Plugins, Backend Modules, CLI commands and Fluid Widgets.

In TYPO3 v8, CLI commands have been migrated to Symfony Console.

Since TYPO3 v9, Backend Requests are not using RequestHandlers anymore.

In TYPO3 v10, the registration of custom RequestHandlers has been moved from TypoScript to PHP files (during build time).

In TYPO3 v11, Fluid Widgets have been removed.

The only available support is for Frontend requests (plugin), which could have been overridden by custom implementions.

From TYPO3 v12.0 onwards, Extbase Bootstrap for plugins is now calling the Extbase dispatcher directly, without loading possible RequestHandlers anymore.

This change removes a layer for each request of a plugin, and thus, a layer of indirection.

It is not possible anymore to implement custom RequestHandlers, as all related functionality has been removed.

Impact

Registration of custom RequestHandlers will not have any effect anymore.

Affected Installations

TYPO3 installations with extensions registering custom Extbase RequestHandlers. This can be checked if an extension provides a Configuration/Extbase/RequestHandlers.php file or using the extension scanner, which will report any usage of the now removed \TYPO3\CMS\Extbase\Mvc\RequestHandlerInterface.

Migration

It is recommended to avoid custom RequestHandlers, as their use case is limited. For TYPO3 v12-only support, custom RequestHandlers and their implementation can be fully removed and developed differently.

For Frontend plugins, it is still possible to use a different bootstrap than the \TYPO3\CMS\Extbase\Core\Bootstrap class, via TypoScript.

For backend modules, custom routeTargets can be defined in the module registration concept.

Using the Decorator pattern is usually good practice to achieve such functionality.