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This repository has been archived by the owner on May 20, 2021. It is now read-only.


This repo is deprecated and was integrated into nixpkgs in NixOS/nixpkgs#108138


Converts yarn.lock files into nix expression.

  1. Make yarn and yarn2nix available in your shell.
    cd $GIT_REPO
    nix-env -i yarn2nix -f .
    nix-env -i yarn -f .
  2. Go to your project dir
  3. If you have not generated a yarn.lock file before, run
    yarn install
  4. Create a yarn.nix via:
    yarn2nix > yarn.nix
  5. Create a default.nix to build your application (see the example below)


Make sure to generate the lock file with yarn >= 1.10.1

Example default.nix

For example, for the front-end of weave's microservice reference application:

with (import <nixpkgs> {});
with (import /home/maarten/code/nixos/yarn2nix { inherit pkgs; });
rec {
  weave-front-end = mkYarnPackage {
    name = "weave-front-end";
    src = ./.;
    packageJSON = ./package.json;
    yarnLock = ./yarn.lock;
    # NOTE: this is optional and generated dynamically if omitted
    yarnNix = ./yarn.nix;

note: you must modify /home/maarten/code/nixos/yarn2nix

To make this work nicely, I exposed the express server in server.js as a binary:

  1. Add a bin entry to packages.json with the value server.js
  2. Add #!/usr/bin/env node at the top of the file
  3. chmod +x server.js

Testing the example

  1. Run nix-build In the front-end directory. Copy the result path.
  2. Create an isolated environment cd /tmp; nix-shell --pure -p bash.
  3. /nix/store/some-path-to-frontend/bin/weave-demo-frontend

Run tests locally



nix-build fails with "found changes in the lockfile" error

yarn2nix runs on the beginning of build to ensure that yarn.lock is correct (and to collect nix-expressions if you haven't provided them). So, if there is something wrong, yarn2nix tries to change the lockfile, but fails and aborts, as it is run with --no-patch flag (as we can't let changes inside of nix-build).

It can sometimes give false-positives, so the solution at the moment is running yarn2nix --no-nix to patch the lockfile in place (the flag is just to avoid config spam, unless you're up to write yarn.nix).


yarn2nix is released under the terms of the GPL-3.0 license.