Basic nix haskell setup

init-haskell.sh

#!/usr/bin/env bash
set -Eeuxo pipefail

# Set up git
git init
gitignore haskell
echo '*.cabal' >> .gitignore

# Set up niv
niv init
niv add hercules-ci/ghcide-nix
niv add -n iohk-nixpkgs input-output-hk/nixpkgs -b a8f81dc037a5977414a356dd068f2621b3c89b60
niv add -n iohk-hnix input-output-hk/haskell.nix -b master

export author="Asad Saeeduddin"
export email="[email protected]"
export ghc="ghc865"
export projectname=${PWD##*/}

# Create hpack project
cat <<EOF > ./package.yaml
spec-version: 0.30.0
name: $projectname
author: ${author}
maintainer: ${email}
license: MIT

build-type: Simple

source-dirs: src
dependencies:
- { name: "base", version: '>=4.12 && <4.13' }

ghc-options: -Wall
default-extensions:
- GADTs

- StandaloneDeriving

- ScopedTypeVariables
- RankNTypes
- QuantifiedConstraints

- TypeApplications
- TypeOperators
- MultiParamTypeClasses

- ConstraintKinds
- DataKinds
- PolyKinds
- KindSignatures

- FlexibleInstances
- FlexibleContexts

library: {}
executable:
  main: Main.hs
EOF

mkdir src

cat <<EOF > ./src/Main.hs
module Main where

main :: IO ()
main = putStrLn "Hello, Haskell!"
EOF

cat <<EOF > ./hie.yaml
cradle: { cabal: {} }
EOF

# Add default.nix
cat <<EOF > ./default.nix
let
  sources = import ./nix/sources.nix;
  compilerVersion = "${ghc}";
  pkgs = (import sources.iohk-nixpkgs) (import sources.iohk-hnix);
in
pkgs.haskell-nix.cabalProject {
  src = pkgs.haskell-nix.haskellLib.cleanGit { src = ./.; };
  ghc = pkgs.buildPackages.pkgs.haskell-nix.compiler.\${compilerVersion};
}
EOF

cat << EOF > ./shell.nix
let
  sources = import ./nix/sources.nix;
  compilerVersion = "${ghc}";
  ghcide = (import sources.ghcide-nix {})."ghcide-\${compilerVersion}";
  pkgs = import sources.iohk-nixpkgs {};
  hspkgs = import ./default.nix;
in
hspkgs.shellFor {
  withHoogle = true;
  buildInputs = [ ghcide pkgs.haskellPackages.ghcid ];
}
EOF

# Create direnv file
# TODO: Remove the grep stuff once https://github.com/hercules-ci/ghcide-nix/issues/26 is resolved
cat << 'EOF' > .envrc
use nix
source <(grep 'export NIX_' $(which ghc))
EOF

cat << 'EOF' > CACHES.md
This project uses various nix expressions for building code. In order to avoid building a huge amount of stuff at once, you might want to enable the following [cachix](https://cachix.org/) caches:

- nix-tools
- hercules-ci

EOF

git add .

direnv allow