[Nix-dev] How to help remedy build errors of Haskell packages in Nixpkgs

[Peter Simons]

Hi Mateusz,

 > Consider the log at <http://hydra.cryp.to/build/164802/log/raw>. It
 > seems like it would be easy to fix with a patch file doing the extra
 > imports or whatever it takes. Is doing this encouraged?

this particular build failure is a good example for a fix that you
*should* commit, IMHO.

Personally, I shy away from committing build fixes only if the patch
would be inappropriately intrusive, i.e. if it would modify the API of
the package and/or change how the library behaves from the perspective
of its users.

I also hesitate to commit fixes that require the addition of a patch
file to the Nixpkgs source tree, because those files are easily
overlooked during updates, so we might end up having the file laying
around in the repository even though no build refers to it. If patch
files can be downloaded from somewhere else -- like Github --, though,
this is no issue: I just add a fetchurl call to the 'patches' attribute.

I hope this helps,
Peter