Comment # 2 on bug 1165483 from Benjamin Zeller

(In reply to Ladislav Slez�k from comment #1)
> YaST actually uses libzypp to find the unneeded packages, it just calls
> "status().isUnneeded()"
> (https://github.com/libyui/libyui-qt-pkg/blob/
> 96a1c6bb9657251b8145bdad9eb4ebd20695c648/src/YQPkgClassFilterView.cc#L248).
> 
> How that "unneeded" status is evaluated is a question for the libzypp
> developers...

>From what I can see, the "unneeded" status is actually evaluated by libsolv:
https://github.com/openSUSE/libzypp/blob/master/zypp/solver/detail/SATResolver.cc#L133

Something in the metadata?