From f1a52ab0b850f502ab7d74906d599509da659570 Mon Sep 17 00:00:00 2001
From: Trolli Schmittlauch <t.schmittlauch@orlives.de>
Date: Wed, 18 Mar 2020 23:53:43 +0100
Subject: [PATCH] re-structure Nix environment to make use of compiler and
 nixpkgs pinning

---
 Hash2Pub/default.nix | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/Hash2Pub/default.nix b/Hash2Pub/default.nix
index d3107d3..938bcc0 100644
--- a/Hash2Pub/default.nix
+++ b/Hash2Pub/default.nix
@@ -1,15 +1,23 @@
-{ pkgs ? import <nixpkgs> {} }:
+{ pkgs ? import (
+  builtins.fetchGit {
+    name = "nixpkgs-pinned";
+    url = https://github.com/NixOS/nixpkgs/;
+    ref = "refs/heads/release-20.03";
+    rev = "6bbdce2b15665af6310069cc4f1e667e426c4356";
+  }) {},
+  compiler ? "ghc865"
+}:
 
 let
-  inherit (pkgs) haskellPackages;
-  drv = haskellPackages.callCabal2nix "Hash2Pub" ./. {};
+  hp = pkgs.haskell.packages."${compiler}";
+  drv = hp.callCabal2nix "Hash2Pub" ./. {};
 in
 {
   my_project = drv;
-  shell = haskellPackages.shellFor {
+  shell = hp.shellFor {
     withHoogle = true;
     packages = p: [ drv ];
-    buildInputs = with pkgs.haskellPackages;
+    buildInputs = with hp;
       [
         haddock
         cabal-install