From d1ed4f2f0453b78dfd14a48e9250776cdb2d371a Mon Sep 17 00:00:00 2001
From: Rodney Lorrimar <rodney.lorrimar@iohk.io>
Date: Wed, 13 Feb 2019 15:08:49 +1000
Subject: [PATCH] Allow users to override hackage.nix and stackage.nix revision
 pins

This would be useful if the project needs to stay with an old version
of haskell.nix but use recent version of hackage.nix/stackage.nix.

Normally latest haskell.nix and latest hackage/stackage are best.
---
 default.nix | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/default.nix b/default.nix
index 8face6ba..8dcccac6 100644
--- a/default.nix
+++ b/default.nix
@@ -1,4 +1,9 @@
 { pkgs ? import <nixpkgs> {}
+
+# You can provide different pins for hackage.nix and stackage.nix if required.
+# It's also possible to override these sources with NIX_PATH.
+, hackageSourceJSON ? ./hackage-src.json
+, stackageSourceJSON ? ./stackage-src.json
 }:
 
 let
@@ -31,14 +36,14 @@ let
   # All packages from Hackage as Nix expressions
   hackage = import (fetchExternal {
     name     = "hackage-exprs-source";
-    specJSON = ./hackage-src.json;
+    specJSON = hackageSourceJSON;
     override = "hackage";
   });
 
   # The set of all Stackage snapshots
   stackage = import (fetchExternal {
     name     = "stackage-snapshot-source";
-    specJSON = ./stackage-src.json;
+    specJSON = stackageSourceJSON;
     override = "stackage";
   });