Use nix and direnv

Author: asterite

.envrc

@@ -0,0 +1,33 @@
+ssh-add -K &> /dev/null || true
+
+my_ssh_auth_sock=$SSH_AUTH_SOCK
+
+
+# Usage: use nix_shell
+#
+# Works like use_nix, except that it's only rebuilt if the shell.nix or shell.nix file changes.
+# This avoids scenarios where the nix-channel is being updated and all the projects now need to be re-built.
+#
+# To force the reload the derivation, run `touch shell.nix`
+use_nix_shell() {
+  local nixcache=".direnv.cache"
+  local tempfile=
+
+  if [[ ! -e "$nixcache" ]] || [[ ".envrc" -nt "$nixcache" ]] || [[ "shell.nix" -nt "$nixcache" ]] || [[ "shell.nix" -nt "$nixcache" ]]; then
+    tempfile="$(mktemp "$nixcache.XXXXXX")"
+    nix-shell --show-trace --run 'direnv dump' > "$tempfile" && mv "$tempfile" "$nixcache"
+    rm -f "$tempfile"
+    tempfile=
+  fi
+  direnv_load cat "$nixcache"
+  for f in $(git ls-files '*.nix'); do
+    watch_file $f
+  done
+}
+
+# Configure a custom nix Cache
+export NIX_CONF_DIR="$(pwd)"
+
+use_nix_shell
+
+export SSH_AUTH_SOCK=$my_ssh_auth_sock

.gitignore

@@ -32,3 +32,4 @@ cabal.sandbox.config
 test/index.html
 *.cabal
 binaries
+.direnv.cache

nix/pkgs.nix

@@ -0,0 +1,36 @@
+let
+  fetch = { rev, sha256 }:
+    builtins.fetchTarball {
+      url = "https://github.com/NixOS/nixpkgs/archive/${rev}.tar.gz";
+      sha256 = sha256;
+    };
+
+
+  config = {
+    packageOverrides = pkgs: rec {
+      haskellPackages = pkgs.haskellPackages.override {
+        overrides = haskellPackagesNew: haskellPackagesOld: rec {
+          # Example of an override:
+          # dotenv = haskellPackagesNew.callPackage ./dotenv.nix { };
+        };
+      };
+    };
+  };
+
+  pkgsPath = fetch {
+    # This comes from https://nixos.org/channels/
+    #
+    # Pick a release (e.g. nixpkgs-18.09-darwin) and then open the `git-revision`
+    # file. It will contain a rev like this.
+    #
+    # Example: https://releases.nixos.org/nixpkgs/18.09-darwin/nixpkgs-darwin-18.09pre154040.58fbebc4ea5/git-revision
+    rev = "9ec7625cee5365c741dee7b45a19aff5d5d56205";
+
+    # Generate this sha using the following command:
+    #
+    # $ nix-prefetch-url --unpack --type sha256 https://github.com/NixOS/nixpkgs/archive/<rev>.tar.gz
+    sha256 = "0rh26fhdvnp9ssk8g63ysyzigw9zg43k9bd2fzrvhrk75sav723h";
+  };
+in {
+  pkgs = import pkgsPath { config = config; };
+}

shell.nix

@@ -0,0 +1,23 @@
+{ pkgs ? (import ./nix/pkgs.nix).pkgs, ghc ? pkgs.ghc }:
+pkgs.haskell.lib.buildStackProject {
+  inherit ghc;
+  name = "jetpack";
+  buildInputs = [
+    pkgs.gcc
+    pkgs.libiconv
+    pkgs.ncurses
+    pkgs.nodejs-10_x
+    pkgs.packer
+    pkgs.pcre
+    pkgs.pkgconfig
+    pkgs.stack
+    pkgs.zlib
+  ] ++
+    (if pkgs.stdenv.system == "x86_64-darwin" then
+      [
+        # MacOS dependency of http-client-tls haskell lib, used by content_creation binary.
+        pkgs.darwin.apple_sdk.frameworks.Cocoa
+        pkgs.darwin.apple_sdk.frameworks.CoreServices
+      ]
+    else []);
+}

stack.yaml

@@ -3,3 +3,6 @@ extra-package-dbs: []
 packages:
 - '.'
 resolver: lts-13.30
+nix:
+  enable: true
+  shell-file: shell.nix