difficult-purescript-nix

difficult-purescript-nix is a flakes-friendly (and more … difficult) alternative to easy-purescript-nix.

How do I use it?

difficult-purescript-nix is intended to be consumed as a flake input. You can then apply inputs.difficult-purescript-nix.overlays.default, which will add the attribute set purescriptPackages to your package set. This contains the following packages:

• purs
• spago
• purs-tidy
• purescript-language-server
• purescript-psa / psa
• pulp
• purty
• pscid

Most of these also contain specific versions. For non-versioned packages, e.g. purescriptPackages.pscid, the package is simply an alias to nodePackages_latest. For versioned dependencies (excluding purs and spago) pre-built packages are fetched from NPM using an indirect invocation of buildNpmPackage (each versioned dependency corresponds to a directory in pkgs/<pkgs>/<version> that contains a dummy package.json and package-lock.json, each containing only the target package in its dependencies field).

Example

Here is a (contrived) example of using difficult-purescript-nix in your own flake:

{
  inputs = {
    flake-parts.url = "github:hercules-ci/flake-parts";
    difficult-purescript-nix = "github:ngua/difficult-purescript-nix";
    # You can also easily do the opposite to make `difficult-purescript-nix`
    # use your own version of `nixpkgs`
    nixpkgs.follows = "difficult-purescript-nix/nixpkgs";
  };

  outputs = { self, nixpkgs, flake-parts, ... }@inputs:
    flake-parts.lib.mkFlake { inherit inputs; } {
      systems = nixpkgs.lib.systems.flakeExposed;

      perSystem = { config, pkgs, lib, system, ... }:
        {
          # This is just an example to demonstrate applying
          # the overlay exposed by the flake
          _module.args.pkgs = import nixpkgs {
            inherit system;
            overlays = [
              inputs.difficult-purescript-nix.overlays.default
            ];
          };

          legacyPackages = {
            inherit (pkgs.purescriptPackages) purs-0_15_4;
          };
        };
    };
}

Other uses

You can also run, try, or install packages from difficult-purescript-nix conveniently using the new nix CLI. All of the Purescript packages available from overlays.default are also exposed by the flake via the legacyPackages (under the namespace purescriptPackages) and packages outputs. For example:

Run a specific version of purs

nix run github:ngua/difficult-purescript-nix#purs-0_14_2 -- --version

Install a package to your profile

nix profile install github:ngua/difficult-purescript-nix#purs-tidy-0_7_2

Show all available packages:

nix flake show github:ngua/difficult-purescript-nix

When should I use it?

As mentioned above, this project is a flake-native adaptation of easy-purescript-nix. I would recommend using difficult-purescript-nix over the latter in the following situations:

• You want or require a flakes-first workflow
• You explicitly want Purescript packages exposed as an overlay

In contract, I would recommend easy-purescript-nix instead, if:

• You can’t or don’t want to use flakes
• You want more options for Purescript packages (easy-purescript-nix exposes a few more packages than this repository)

Caveats

Systems

As with easy-purescript-nix and indeed nixpkgs, difficult-purescript-nix fetches pre-built binaries for spago and purs from their GitHub releases. This has the definite advantage of never requiring a build from source, but also means that only x86_64-linux and x86_64-darwin are really supported. In the future, I’d like to try to see if it’s possible to build both projects from source, at least on aarch64 platforms, and expand the number of systems that difficult-purescript-nix supports (this will also be affected by Spago’s ongoing Purescript rewrite).