Add nix shell

Author: lukasz-golebiewski

default.nix

@@ -0,0 +1,10 @@
+{ pkgs ? import ./haskell-pkgs.nix
+, haskellCompiler ? "ghc8101"
+}:
+pkgs.haskell-nix.cabalProject {
+  src = pkgs.haskell-nix.haskellLib.cleanGit {
+    name = "stylish-haskell";
+    src = ./.;
+  };
+  compiler-nix-name = haskellCompiler;
+}

haskell-pkgs.nix

@@ -0,0 +1,18 @@
+let
+  # Fetch the latest haskell.nix and import its default.nix
+  haskellNix = import (builtins.fetchTarball{
+    url = "https://github.com/input-output-hk/haskell.nix/archive/f6663a8449f5e4a7393aa24601600c8f6e352c97.tar.gz";
+  }) {};
+
+# haskell.nix provides access to the nixpkgs pins which are used by our CI,
+# hence you will be more likely to get cache hits when using these.
+# But you can also just use your own, e.g. '<nixpkgs>'.
+  nixpkgsSrc = haskellNix.sources.nixpkgs-2003;
+
+# haskell.nix provides some arguments to be passed to nixpkgs, including some
+# patches and also the haskell.nix functionality itself as an overlay.
+  nixpkgsArgs = haskellNix.nixpkgsArgs;
+
+# import nixpkgs with overlays
+in
+  import nixpkgsSrc nixpkgsArgs

shell.nix

@@ -0,0 +1,27 @@
+{ pkgs ? import ./haskell-pkgs.nix}:
+
+let
+  hsPkgs = import ./. { inherit pkgs; };
+in
+  hsPkgs.shellFor {
+    # Include only the *local* packages of your project.
+    # packages = ps: with ps; [
+    # ];
+
+    # Builds a Hoogle documentation index of all dependencies,
+    # and provides a "hoogle" command to search the index.
+    # withHoogle = true;
+
+    # You might want some extra tools in the shell (optional).
+    # Some common tools can be added with the `tools` argument
+    tools = { cabal = "3.2.0.0"; hlint = "2.2.11"; };
+    # See overlays/tools.nix for more details
+
+    # Some you may need to get some other way.
+    buildInputs = with pkgs.haskellPackages;
+      [ ghcid ];
+
+    # Prevents cabal from choosing alternate plans, so that
+    # *all* dependencies are provided by Nix.
+    exactDeps = true;
+  }