elm2nix

Convert an Elm project into Nix expressions.

It consists of multiple commands:

• elm2nix convert: Given elm.json in current directory, all dependencies are parsed and their sha256sum calculated
• elm2nix snapshot: Downloads snapshot of https://package.elm-lang.org/all-packages json and converts into binary registry.dat used by elm-compiler as a cache
• elm2nix init: Generates default.nix that glues everything together

Assumptions

Supports Elm 0.19.1

Installation

From nixpkgs (recommended)

Make sure you have up to date stable or unstable nixpkgs channel.

$ nix-env -i elm2nix

From source

$ git clone https://github.com/domenkozar/elm2nix.git
$ cd elm2nix
$ nix-env -if .

Usage

$ git clone https://github.com/evancz/elm-todomvc.git
$ cd elm-todomvc
$ elm2nix init > default.nix
$ elm2nix convert > elm-srcs.nix
# generates ./registry.dat
$ elm2nix snapshot
$ nix-build
$ chromium ./result/Main.html

Running tests (as per CI)

$ ./scripts/tests.sh

FAQ

Why is mkDerivation inlined into default.nix?

As it’s considered experimental, it’s generated for now. Might change in the future.

How do I use elm2nix with ParcelJS and Yarn?

Instead of running elm2nix init, create a default.nix with the following derivation:

{ pkgs ? import <nixpkgs> {}
}:

let
  yarnPkg = pkgs.mkYarnPackage {
    name = "myproject-node-packages";
    src = pkgs.lib.cleanSourceWith {
      src = ./.;
      name = "myproject-node-packages.json";
      filter = name: type: baseNameOf (toString name) == "package.json";
    };
    yarnLock = ./yarn.lock;
    publishBinsFor = ["parcel"];
  };
in pkgs.stdenv.mkDerivation {
  name = "myproject-frontend";
  src = pkgs.lib.cleanSource ./.;

  buildInputs = with pkgs.elmPackages; [
    elm
    elm-format
    yarnPkg
    pkgs.yarn
  ];

  patchPhase = ''
    rm -rf elm-stuff
    ln -sf ${yarnPkg}/node_modules .
  '';

  shellHook = ''
    ln -fs ${yarnPkg}/node_modules .
  '';

  configurePhase = pkgs.elmPackages.fetchElmDeps {
    elmPackages = import ./elm-srcs.nix;
    elmVersion = "0.19.1";
    registryDat = ./registry.dat;
  };

  installPhase = ''
    mkdir -p $out
    parcel build --dist-dir $out index.html
  '';
}