Mapping non-Haskell dependencies to Nixpkgs

Cabal files may contain dependencies to external non-Haskell dependencies via:

If there is a pkgs attribute in Nixpkgs that matches the name given in the Cabal file, then it will be added as a dependency (see the output of cabal-to-nix). Otherwise, there needs to be a mapping from Cabal file names (decided by the package author) to Nix package identifiers.

Nixpkgs overlay

The user may solve it by themself by overriding Nixpkgs and adding a package alias. For example:

nixpkgs.overlays = [
  (self: super: {
    icuuc =;
    icui18n =;
    icudata =;

The user can map package(s) in Nixpkgs to a pkgconfig-depends name by overlaying the haskell-nix.extraPkgconfigMappings attribute:

nixpkgs.overlays = [
  (self: super: {
    haskell-nix = super.haskell-nix // {
      extraPkgconfigMappings = super.haskell-nix.extraPkgconfigMappings // {
          # String pkgconfig-depends names are mapped to lists of Nixpkgs
          # package names
          "SDL_gpu" = [ "SDL_gpu" ];

Replace libraries of components

If a component is missing a dependency it can be added via modules. For example:

project = pkgs.haskell-nix.project' {
  src = self;
  compiler-nix-name = "ghc8102";
  modules = [{
    # Replace `extra-libraries` dependencies
    packages.X11.components.library.libs = pkgs.lib.mkForce (with pkgs.xorg;
        [ libX11 libXrandr libXext libXScrnSaver libXinerama ]);

Mapping in Haskell.nix

Alternatively, if the name is commonly used, an alias can be added to the Haskell.nix sources, so that it's solved for all users.

  • lib/pkgconf-nixpkgs-map.nix — for pkgconfig-depends.

    Each mapping entry is a list of packages.

  • lib/system-nixpkgs-map.nix — for build-tool-depends, frameworks, extra-libraries, etc.

    Each name can be mapped to:

    1. A single package from nixpkgs.
    2. null — eliminates the dependency
    3. A list of packages — sometimes needed for dependencies such as X11.

Tip: Open a PR

Please go ahead and open a pull request to improve the package mappings.