TYPO3 Core

After discussing with a few people on slack (Hello again, Maddy ^^) and investing a few hours every now and then, I decided to file an issue, as this is either a bug, a missing feature, or undocumented.

Situation
You have a full-blown extension (tx_news in this case) that provides almost everything you need. I want to extend that existing model and be able to use new fields through the existing tx_news controller/view without having to copy-paste everything into a custom controller (as this would result in unneeded maintenance work).

What I did * Set up tx_news * integrated the list plugin on a page * wrote some news and categorized them * set up extension attached to this issue * included static typoscript from it

Expectation
News categories' classes are mapping properly to my new model.

Result
News categories are mapped, however, all attributes except uid, pid and _localizedUid are NULL instead of having the original value. When the static typoscript from this ext is removed, catgeories are mapped again to tx_news, with proper attribute values.

Is this even possible? I feel it should, otherwise, the mapping configuration properties wouldn't make much sense IMHO.