Deprecation: #84196 - Backend controller actions do not receive prepared response

See Issue #84196

Description

The second argument to backend and eID controller actions has been marked as deprecated. Controllers should create a response object implementing Psr\Http\Message\ResponseInterface on their own instead of relying on a prepared response.

The signature of controller actions should look like

public function myAction(ServerRequestInterface $request): ResponseInterface

Impact

Controllers should typically instantiate one of the three core response classes and return it:

public function myAction(ServerRequestInterface $request): ResponseInterface
{
    return new HtmlResponse('content');
    return new JsonResponse($jsonArray);
    return new RedirectResponse($url);
}

Affected Installations

Instances with extensions that register backend controllers (eg. modules) or eID may be affected.

The dynamic scanning for not yet adapted controller actions relies on reflection and costs some CPU cycles. If all affected extensions have been adapted, the feature toggle simplifiedControllerActionDispatching should be enabled. This can be managed in the backend Settings -> Configure Installation-Wide Options module.

Migration

See above code examples for typical controller actions return values and signature.