[Nix-dev] haskell dev environment, ghc non-determinism and binary cache interaction

[Peter Simons]

Hi Miguel,

 > Would the fix in this case be to add versions of all diagrams libs
 > pinned at 1.12 by adding them to "extra packages" in hackage2nix.hs,
 > wait that they appear in nixpkgs suffixed with _1_12 and then have
 > ihaskell-diagrams depend on diagrams_1_12 instead of diagrams ?

yes, that would be one way to fix the build error, although it's the
least desirable option, because in all likelihood no-one removes those
packages from the list once the ihaskell-diagrams build has been fixed
and then we'll end up distributing and building a lot of dead package
versions that nobody needs.

What should be done is this:

 1) Contact the broken package's authors and inform them of the issue so
    that they can release a new version to Hackage.

 2) No, really, contact upstream!!! We are not the only distribution
    that has these kind of problems, and by helping make Hackage
    consistent, you're providing a service to the community that is
    genuinely more useful than just fixing the build for Nixpkgs.

 3) Jailbreak the build to check whether it succeeds once the version
    constraints are removed from the Cabal file.

 4) If all these options don't help, then add older versions of the
    dependencies and configure an override.

Best regards,
Peter