2022-12-16

This is the first post in a series about stacklock2nix. The next post is about building Dhall with stacklock2nix.

This post uses stacklock2nix to build the PureScript compiler with Nix. PureScript is a non-trivial Haskell project, but it is not too complicated. It is good as an initial example of using stacklock2nix.

The following commit adds a flake.nix to the PureScript repo that can be used to build with Nix:

https://github.com/cdepillabout/purescript/commit/b78324382f44e7d75ff5175e535df33a39f2e62e

This flake.nix is based on the easy example of stacklock2nix.

This post explains how to use this flake.nix.

What can you do with this flake.nix?

First, lets clone the above code locally with the following commands:

$ git clone git@github.com:cdepillabout/purescript.git
$ cd purescript/
$ git checkout build-with-stacklock2nix

From here, you can use the flake.nix to build PureScript:

$ nix build -L

After building, the compiler (called purs) should be available:

$ ./result/bin/purs --version
0.15.7 [development build; commit: UNKNOWN]

You can also jump into a development shell that has tools like cabal-install and HLS available:

$ nix develop -L

From here, you can build PureScript with cabal:

$ cabal build
...
$ cabal run exe:purs -- --version
0.15.7 [development build; commit: df5fcff1c396d520e8543d5d85ce1455e56e2696 DIRTY]

You can use other normal commands like cabal test, cabal repl, etc.

Conclusion

PureScript is a large, non-trivial, single-package Haskell project. Building it using stacklock2nix is relatively straight-forward. Few Nix overrides are necessary for getting everything to build. stacklock2nix makes it easy to build a Haskell project with Nix, given that you already have a stack.yaml and stack.yaml.lock file.

tags: purescript, haskell, nixos