From e82440741295543769fa79ae05519d58fcb81b08 Mon Sep 17 00:00:00 2001
From: Ben Sima <ben@bsima.me>
Date: Fri, 3 Apr 2020 15:37:10 -0700
Subject: Factor haskell packages into overlays

---
 biz.nix      | 35 +----------------------------------
 default.nix  |  3 ++-
 overlays.nix | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 35 deletions(-)
 create mode 100644 overlays.nix

diff --git a/biz.nix b/biz.nix
index f28e223..1194758 100644
--- a/biz.nix
+++ b/biz.nix
@@ -12,39 +12,6 @@ let
   seq = ls: builtins.filter (x: x!= null) ls;
   depsToPackageSet = packageSet: deps:
     map (s: builtins.getAttr s packageSet) deps;
-
-  # do the build...
-
-  claySrc = pkgs.fetchFromGitHub {
-    owner = "sebastiaanvisser";
-    repo = "clay";
-    rev = "cc7729b1b42a79e261091ff7835f7fc2a7ae3cee";
-    sha256 = "1vd67976lvi5l4qq18zy6j44apynkl44ps04p8vwfx4gzr895dyp";
-  };
-
-  ghc865_ = pkgs.haskell.packages.ghc865.override (oldAttrs: {
-    overrides = with pkgs.haskell.lib; self: super: {
-      clay = self.callCabal2nix "clay" claySrc {};
-      wai-middleware-metrics = dontCheck super.wai-middleware-metrics;
-    };
-  });
-
-  # ghcjs-8.6.0.1
-  ghcjs_ = pkgs.haskell.packages.ghcjs.override (oldAttrs: {
-    overrides = with pkgs.haskell.lib; self: super: {
-      QuickCheck = dontCheck super.QuickCheck;
-      base-compat-batteries = dontCheck super.http-types;
-      clay = dontCheck (self.callCabal2nix "clay" claySrc {});
-      comonad = dontCheck super.comonad;
-      http-types = dontCheck super.http-types;
-      network-uri= dontCheck super.network-uri;
-      scientific = dontCheck super.scientific; # takes forever
-      servant = dontCheck super.servant;
-      tasty-quickcheck = dontCheck super.tasty-quickcheck;
-      time-compat = dontCheck super.time-compat;
-    };
-  });
-
 in {
   buildGhc = main:
     let
@@ -57,7 +24,7 @@ in {
       deps = lists.flatten (seq
         (map (builtins.match "^-- : dep ([[:alnum:]._-]*)$")
           (lines content)));
-      ghc = ghc865_.ghcWithHoogle (hp: depsToPackageSet hp deps);
+      ghc = pkgs.haskell.packages.ghc865.ghcWithHoogle (hp: depsToPackageSet hp deps);
     in stdenv.mkDerivation {
       name = module;
       version = "0";
diff --git a/default.nix b/default.nix
index 60b67b3..b15b925 100644
--- a/default.nix
+++ b/default.nix
@@ -1,6 +1,7 @@
 let
   nixpkgs-tar = builtins.fetchTarball (import ./nixpkgs.nix);
-  nixpkgs = import "${nixpkgs-tar}" {};
+  overlay = import ./overlays.nix;
+  nixpkgs = import "${nixpkgs-tar}" { overlays = [ overlay ]; };
   nixos = import "${nixpkgs-tar}/nixos";
   # TODO(bsima): buildNixOS should be split into multiple functions that each
   # return one thing, instead of a single function that returns multiple things
diff --git a/overlays.nix b/overlays.nix
new file mode 100644
index 0000000..5da2957
--- /dev/null
+++ b/overlays.nix
@@ -0,0 +1,35 @@
+self: super:
+
+let
+ claySrc = super.pkgs.fetchFromGitHub {
+    owner = "sebastiaanvisser";
+    repo = "clay";
+    rev = "cc7729b1b42a79e261091ff7835f7fc2a7ae3cee";
+    sha256 = "1vd67976lvi5l4qq18zy6j44apynkl44ps04p8vwfx4gzr895dyp";
+  };
+in {
+  haskell = super.haskell // {
+    packages = super.haskell.packages // {
+      ghc865 = super.haskell.packages.ghc865.override (old: {
+        overrides = with super.pkgs.haskell.lib; self: super: {
+          clay = self.callCabal2nix "clay" claySrc {};
+          wai-middleware-metrics = dontCheck super.wai-middleware-metrics;
+        };
+      });
+      ghcjs = super.haskell.packages.ghcjs.override (old: {
+        overrides = with super.haskell.lib; self: super: {
+          QuickCheck = dontCheck super.QuickCheck;
+          base-compat-batteries = dontCheck super.http-types;
+          clay = dontCheck (self.callCabal2nix "clay" claySrc {});
+          comonad = dontCheck super.comonad;
+          http-types = dontCheck super.http-types;
+          network-uri= dontCheck super.network-uri;
+          scientific = dontCheck super.scientific; # takes forever
+          servant = dontCheck super.servant;
+          tasty-quickcheck = dontCheck super.tasty-quickcheck;
+          time-compat = dontCheck super.time-compat;
+        };
+      });
+    };
+  };
+}
-- 
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