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ceedubs/unison-nix

Nix support for the Unison programming language
Source code at GitHub null
ceedubs/unison-nix.json
{
  "createdAt": "2020-10-09T23:05:20Z",
  "defaultBranch": "trunk",
  "description": "Nix support for the Unison programming language",
  "fullName": "ceedubs/unison-nix",
  "homepage": null,
  "language": "Nix",
  "name": "unison-nix",
  "pushedAt": "2025-11-25T19:06:46Z",
  "stargazersCount": 64,
  "topics": [],
  "updatedAt": "2025-11-26T20:21:04Z",
  "url": "https://github.com/ceedubs/unison-nix"
}

unison-nix

Section titled “unison-nix”

[Nix] support for the [Unison] programming language

usage

Section titled “usage”

NOTE: If you don’t already have Nix installed, follow the instructions on the Nix site.

install Unison code manager

Section titled “install Unison code manager”

If your version of Nix supports [Nix flakes]:

nix profile install github:ceedubs/unison-nix#ucm-bin

Use from home-manager:

In your home-manager’s flake.nix, reference this repository under inputs, e.g.:

unison-lang = {
  url = "github:ceedubs/unison-nix";
  inputs.nixpkgs.follows = "nixpkgs";
};

then add the unison-lang overlay:

pkgs = import nixpkgs {
  inherit system;
  overlays = [ unison-lang.overlay ];
};

Finally, in your home.nix, just add the unison-ucm package as you normally would.

An example is available here.

Older versions of Nix:

nix-env -iA unison-ucm -f https://github.com/ceedubs/unison-nix/archive/trunk.tar.gz

try out Unison without installing it to your PATH/Nix profile

Section titled “try out Unison without installing it to your PATH/Nix profile”

If your version of Nix supports [Nix flakes] !:

nix run github:ceedubs/unison-nix#ucm-bin

Older versions of Nix:

nix-build https://github.com/ceedubs/unison-nix/archive/trunk.tar.gz -A unison-ucm

This will create a symlink named result in your current directory. Now run:

Terminal window
./result/bin/ucm

Once you are done trying out Unison you can rm ./result.

available packages/tools

Section titled “available packages/tools”
  • ucm-bin: a binary release of the Unison code manager
    • This is named unison-ucm in the overlay and for older versions of Nix (pre-flakes)
  • ucm: a release of the Unison code manager built from source (without some of the niceties provided by ucm-bin)
  • vim-unison: a vim plugin providing syntax highlighting for Unison files
    • This is provided as vimPlugins.vim-unison in the overlay
  • VS Code extensions
  • overlay: A nixpkgs overlay that adds the Unison packages in the relevant places (ex: vim-unison in vimPlugins.vim-unison)
  • buildUnisonShareProject a function for turning functions in a Unison Share project into executable derivations.
    • See unison-nix-snake for an example.
    • See [nix/build-share-project.nix]!(nix/build-share-project.nix) for documentation.
  • buildUnisonFromTranscript a lower-level function for turning a Unison transcript into an executable derivation.
    • See [nix/build-from-transcript.nix]!(nix/build-from-transcript.nix) for documentation.

In the future this repository would be a natural home for derivations for other Unison tools.

NOTE: the unison github repo repo has a flake.nix that you can use with nix develop to get an environment with the expected versions of stack, ormolu, etc.

FAQ

Section titled “FAQ”

Fabricated/Anticipated Questions

Why don’t these derivations live in nixpkgs?

Section titled “Why don’t these derivations live in nixpkgs?”

The [nixpkgs repository][nixpkgs] was the original home of Unison Nix dervations, but Unison is evolving quickly and getting Unison updates merged into nixpkgs turned out to be a bottleneck in getting these new features and bug fixes out to Unison users.

[Nix] !: https://nixos.org/ [Nix Flakes] !: https://nixos.wiki/wiki/Flakes [nixpkgs] !: https://github.com/nixos/nixpkgs [Stack] !: https://docs.haskellstack.org/en/stable/README/ [Unison] !: https://www.unisonweb.org/