Before using haskell-flake you must first install Nix.
Existing projects
To use haskell-flake in an existing Haskell project, run:
nix flake init -t github:srid/haskell-flake
Open the generated flake.nix and change self'.packages.example to use your package name. For example, if your package is named my-package (with a my-package.cabal file), change example to my-package. Follow the comments along the flake.nix to make any necessary changes to the project configuration.
New projects
To create a new Haskell project, instead, run:
mkdir example && cd ./example
nix flake init -t github:srid/haskell-flake#exampleTemplate
You may also use https://github.com/srid/haskell-template which already uses haskell-flake along with other opinionated defaults.
Under the hood
See this tutorial to understand what it takes to package a Haskell application without haskell-flake.
When nixifying a Haskell project without flake-parts (thus without haskell-flake) you would generally use the raw Haskell infrastructure from nixpkgs. haskell-flake uses these functions, while exposing a simpler modular API on top: your flake.nix becomes more declarative and less imperative.
In addition, compared to using plain nixpkgs, haskell-flake supports:
-
Auto-detection of local packages based on
cabal.projectfile (via haskell-parsers) -
Parse executables from
.cabalfile, to create Flake apps. -
Modular interface to
pkgs.haskell.lib.compose.*(viapackagesandsettingssubmodules) - Composition of dependency overrides, and other project settings, via Project modules
See Getting Started for getting started with haskell-flake.
Next steps
Visit Guide for more details, and Reference for module options.