Use extra-packages in modules/hackage-project.nix

[hamishmack]

This is a step towards removing the dependency on hackage.nix.

Instead of looking up the source for a tool using hackage.nix it lets make-install-plan to it using the cabal planner (based on an extra-packages: entry in a cabal.project file).

[mrkline]

This seems to break stackProject. With:

let haskellSrc = builtins.fetchTarball "https://github.com/input-output-hk/haskell.nix/archive/cc140d188d53692a43a86cc7e4849702a3f04389.tar.gz";
    haskellNix = import haskellSrc {};
    pkgs = import
        haskellNix.sources.nixpkgs
        haskellNix.nixpkgsArgs;
    project = pkgs.haskell-nix.stackProject {
      src = pkgs.haskell-nix.cleanSourceHaskell {
        name = "blah";
        src = ./.;
      };
      modules = [
        { enableProfiling = true;
          enableLibraryProfiling = true;
        }
      ];
    };
in project.shellFor {
    exactDeps = true;
    tools = {
      cabal = "latest";
      hlint = "latest";
      haskell-language-server = "latest";
    };
}

I get

$ nix-shell
error:
...
         at /nix/store/2iva5ci4a20hg1iig1jzkkb6kixvv41s-source/overlays/haskell.nix:970:25:

          969|         stackProject = args: let p = stackProject' args;
          970|             in p.hsPkgs // p;
             |                         ^
          971|

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: undefined variable 'hackage'

       at /nix/store/2iva5ci4a20hg1iig1jzkkb6kixvv41s-source/overlays/haskell.nix:113:47:

          112|                 # The compiler referenced in the stack config
          113|                 compiler = (stack-pkgs.extras hackage).compiler or (pkg-def hackage).compiler;
             |                                               ^
          114|                 patchesModule = ghcHackagePatches.${compiler.nix-name} or {};

[thomasjm]

I noticed the same -- this breaks Haskell.nix for my Stack-based project.