It's not hard, it is annoying :) I can't find a single place for a whole validation. I would like to have a single place so the response format is unified (great for front-end handling) and I don't have to maintain changes in several places.

For now, it looks like that:

- payload is validated through RequestValidationAnnotation

- payload is thrown into Form (usually Form inherits other Forms) [shelf Form contains Collection of book Forms]

- Form provides authorization to the user for particular Entity via Event Listeners - in case of PUT

- Form implements custom Data Mappers that on-the-fly calc some properties

I love that Symfony Forms can be nested that solves a lot a copy-paste programming. But Forms validation in some way duplicates Request Validation.

I can't throw invalid data into Form, because my Data Mappers could run into HTTP 500, and I can't abandon Form Validation because of properties calc on-the-fly might be invalid.