This repository contains a nix develop shell for Haskell. Its primary purpose is to help get a development shell for Haskell quickly and across multiple operating systems (and architectures).

It requires nix to be installed.

Once you have nix installed:

• Add experimental-features = nix-command flakes to your $XDG_CONFIG_HOME/nix/nix.conf file to enable Nix flakes.
• You should manually add necessary substituters and trusted public keys to your /etc/nix/nix.conf:

  allow-import-from-derivation = "true";
  extra-substituters = https://cache.iog.io https://cache.zw3rk.com
  extra-trusted-public-keys = "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=" "loony-tools:pr9m4BkM/5/eSTZlkQyRt57Jz7OMBxNSUiMC4FkcNfk="
  

• Ensure that nix-daemon is running (systemctl status nix-daemon on systemd-based systems).

Then, (on Linux, macOS, windows WSL) you can use:

nix develop github:input-output-hk/devx#ghc96 --no-write-lock-file --refresh

To obtain a haskell development shell for GHC 8.10.7 including cabal-install, as well as hls and hlint. If you are on macOS on an Apple Silicon chip (M1, M2, ...), and want to switch between Intel (x86_64) and Apple Silicon (aarch64), you can do this by simply passing the corresponding --system argument:

nix develop github:input-output-hk/devx#ghc810 --no-write-lock-file --refresh --system x86_64-darwin
# ... or:
nix develop github:input-output-hk/devx#ghc810 --no-write-lock-file --refresh --system aarch64-darwin

If you use direnv, you can integrate this shell by creating an .envrc file with the following content:

# https://github.com/nix-community/nix-direnv A fast, persistent use_nix/use_flake implementation for direnv:
if ! has nix_direnv_version || ! nix_direnv_version 2.3.0; then
  source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/2.3.0/direnvrc" "sha256-Dmd+j63L84wuzgyjITIfSxSD57Tx7v51DMxVZOsiUD8="
fi
# https://github.com/input-output-hk/devx Slightly opinionated shared GitHub Action for Cardano-Haskell projects 
use flake "github:input-output-hk/devx#ghc810-iog"

Refer to direnv and devx guide for more information.

To make this developer shell available in VSCode DevContainer or GitHub CodeSpace, simply add a file named .devcontainer/devcontainer.json with the following content:

{
   "image":"ghcr.io/input-output-hk/devx-devcontainer:x86_64-linux.ghc810-iog",
   "customizations":{
      "vscode":{
         "extensions":[
            "haskell.haskell"
         ],
         "settings":{
            "haskell.manageHLS":"PATH"
         }
      }
   }
}

This configuration will work immediately in GitHub CodeSpace! For local VSCode DevContainer, you need Docker and the VSCode extension. For guidance on this, you can follow the Microsoft tutorial.

It's also advised to enable GitHub CodeSpace prebuilds in your repository settings, follow the instructions provided in the GitHub documentation. This will significantly enhance your development experience by reducing the setup time when opening a new CodeSpace.

List of images available: ghc810-iog, ghc96-iog, ghc810-js-iog, ghc96-js-iog, ghc810-windows-iog, ghc96-windows-iog.

There are multiple compilers available, and usually the latest for each series from 8.10 to 9.6 (a slight delay between the official release announcement and the compiler showing up in the devx shell is expected due to integration work necessary). The current available ones are: ghc810, ghc90, ghc92, ghc94, and ghc96 (these are the same ones as in haskell.nix and may contain patches for defects in the official releases).

There are various flavors available as suffixes to the compiler names (e.g. #ghc810-minimal-iog).

These can then be combined following this schema:

#ghc<ver>[-js|-windows|-static][-minimal][-iog]

For example:

nix develop github:input-output-hk/devx#ghc810-windows-minimal-iog --no-write-lock-file --refresh

... would provide a development shell with a windows cross-compiler as well as cabal, and the IOG specific libraries, but no Haskell Language Server (hls), and no HLint.

A full list of all available devShells can be seen with:

nix flake show github:input-output-hk/devx

The devx shell utilizes haskell.nix for a consistent development environment across platforms. Direct use of haskell.nix allows for greater customization by adapting Nix expressions to specific project needs, haskell.nix turn a Cabal or Stack projects into a Nix expression. For more details, see the haskell.nix documentation.

The devx GitHub Action, alongside other IOG-provided actions, supports automated workflows for Haskell projects. More information can be found in the IOG GitHub Actions repository.