TYPO3 Core

We can not change the method as PageErrorHandlerInterface is an interface and we can't add method arguments – not even optional/nullable ones.
We'd need to add a new StatusAndCongfigurationAwarePageErrorHandlerInterface with a new method.

I think it's not that nice for the core code to have to handle mutliple error handler interface types…

Still it is a good Idea to support dependency injection!

I think I'd rather prefer a new handler type "Factory" (additonal to "PHP" which wouldn't be removed).
The factory would be a container service that implements `PageErrorHandlerFactoryInterface`.

The interface for such factories would look something like this:

interface PageErrorHandlerFactoryInterface {
    public function createErrorHandler(
        int $statusCode,
        ?array $errorHandlerConfiguration = null
    ): PageErrorHandlerInterface;
}

This factory could then instantiate an own implementation of an error handler: That could either be a DI prototype class (shared: false) that contains a setter for $statusCode + $configuration (whatever you actually need) or simply an anonymous class…

Here is an example for an anonymous class:

class MyPageErrorHandlerFactory implements PageErrorHandlerFactoryInterface {

    public function __construct(MyDependency $myDependency) {
        $this->myDependency = $myDependency;
    }

    public function createErrorHandler(
        int $statusCode,
        ?array $errorHandlerConfiguration = null
    ): PageErrorHandlerInterface {
        return new class($myDependency, $statusCode, $errorHandlerConfiguration) implements PageErrorHandlerInterface {
            public function __construct(MyDependency $myDependency, int $statusCode, ?array $errorHandlerConfiguration = null) {
                $this->myDependency = $myDependency;
                $this->status = $statusCode;
            }
            public function handlePageError(ServerRequestInterface $request, string $message, array $reasons = []): ResponseInterface {
                // Do something using $this->myDependency here            
            }
        }
    }
}

The page configuration would looks something like:

errorHandling:
  -
    errorCode: '404'
    errorHandler: Factory
    errorFactoryService: Vendor\ExtensionName\ErrorHandlers\MyPageErrorHandlerFactory
    # or maybe rather
    errorHandlerFactoryService: Vendor\ExtensionName\ErrorHandlers\MyPageErrorHandlerFactory
    # or just (to be discussed)
    errorHandlerFactory: Vendor\ExtensionName\ErrorHandlers\MyPageErrorHandlerFactory

Of course, this is just my taste, I'll ask other core devs whether they would be fine with such interface.

Do you want to try to start coding on that, or should I do?

I like your idea, it seems to be a very elegant solution. Imo, it could even deprecate/supersede the current 'PHP' errorHandler, because having two methods of 'add-your-own-code' might be a bit too much.

Do you want to try to start coding on that, or should I do?

When your colleagues are fine with it, i'll go when you say so ;-) That work would be considered a new feature and go to master only, right?

Is there any news on that feature? I am having a hard time injecting a service into the custom error handling class right now.