From 0fca1ef401cad90821296bab1b1fdcaf11d0d65a Mon Sep 17 00:00:00 2001
From: Matthieu Coudron <mcoudron@hotmail.com>
Date: Wed, 15 Dec 2021 19:00:41 +0100
Subject: [PATCH] build: add flake.nix

run `nix develop` to get a development environment
---
 flake.lock | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 flake.nix  | 47 ++++++++++++++++++++++++++++++++++++++++++
 shell.nix  | 38 ++++++++--------------------------
 3 files changed, 115 insertions(+), 30 deletions(-)
 create mode 100644 flake.lock
 create mode 100644 flake.nix

diff --git a/flake.lock b/flake.lock
new file mode 100644
index 000000000..3f4705262
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,60 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1641205782,
+        "narHash": "sha256-4jY7RCWUoZ9cKD8co0/4tFARpWB+57+r1bLLvXNJliY=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "b7547d3eed6f32d06102ead8991ec52ab0a4f1a7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1644229661,
+        "narHash": "sha256-1YdnJAsNy69bpcjuoKdOYQX0YxZBiCYZo4Twxerqv7k=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "3cecb5b042f7f209c56ffd8371b2711a290ec797",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1646939531,
+        "narHash": "sha256-bxOjVqcsccCNm+jSmEh/bm0tqfE3SdjwS+p+FZja3ho=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "fcd48a5a0693f016a5c370460d0c2a8243b882dc",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 000000000..2a31ca2e5
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,47 @@
+{
+  description = "Generate Nix build instructions from a Cabal file";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system: let
+
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      ghc8107 = pkgs.haskell.packages."ghc8107";
+
+      # modifier used in haskellPackages.developPackage
+      myModifier = hsPkgs: drv:
+        pkgs.haskell.lib.addBuildTools drv ([
+          hsPkgs.cabal-install
+          hsPkgs.haskell-language-server
+        ]);
+
+      mkPackage = hsPkgs:
+          hsPkgs.developPackage {
+            root =  pkgs.lib.cleanSource ./. ;
+            name =  "cabal2nix";
+            returnShellEnv = false;
+            withHoogle = true;
+            modifier = myModifier hsPkgs;
+          };
+
+    in {
+      packages = {
+        cabal2nix = self.packages.${system}.cabal2nix-8107;
+        cabal2nix-8107 = mkPackage ghc8107;
+      };
+
+      devShell = self.packages.${system}.cabal2nix.envFunc {};
+
+      defaultPackage = self.packages.${system}.cabal2nix;
+  });
+}
diff --git a/shell.nix b/shell.nix
index 44f4e07c4..77bbd229b 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,31 +1,9 @@
-{ pkgs ? import <nixpkgs> {} }:
-
+(import (
 let
-  haskellPackages = pkgs.haskellPackages;
-  ghc = haskellPackages.ghcWithHoogle (hps: [
-    hps.ansi-wl-pprint
-    hps.distribution-nixpkgs
-    hps.hackage-db
-    hps.hopenssl
-    hps.hpack
-    hps.language-nix
-    hps.lens
-    hps.optparse-applicative
-    hps.pretty
-    hps.split
-    hps.yaml
-    hps.monad-par
-    hps.monad-par-extras
-    hps.tasty
-    hps.tasty-golden
-  ]);
-
-in pkgs.stdenv.mkDerivation {
-  name = "shell";
-  buildInputs = [
-            ghc
-            haskellPackages.cabal-install
-            haskellPackages.haskell-language-server
-            (pkgs.lib.getLib pkgs.openssl)
-          ];
-}
+    lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  in fetchTarball {
+    url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+    sha256 = lock.nodes.flake-compat.locked.narHash; }
+) {
+  src =  ./.;
+}).shellNix