Oh, and a primer on the overall cabal design would be also very useful! M. Martin Vlk:

Hi folks, I am a beginner cabal hacker and I have been picking issues to fix, labeled with "easy".

My next one is https://github.com/haskell/cabal/issues/2645.

I've been trying to read and feel my way through the code and find where this issue is rooted, but so far I haven't succeeded.

To save me unnecessary effort, could somebody point me at the right modules/functions where soft constraints/preferences are handled and also where the corresponding merging functionality is implemented for hard constraints.

I'll then take it from there, read the code and fix the issue, potentially asking more questions here.

Many Thanks Martin