Merge pull request #392 from LSLeary/flake-module

Apply Patch in Nix Flake; Enable Configuration

flake.nix

@@ -1,20 +1,70 @@
-# This file is maintained by @IvanMalison (github)
+# This file is maintained by @IvanMalison and @LSLeary (github)
+# See xmonad-contrib/NIX.md for an overview of module usage.
 {
   inputs = {
     flake-utils.url = github:numtide/flake-utils;
     git-ignore-nix.url = github:hercules-ci/gitignore.nix/master;
+    unstable.url = github:NixOS/nixpkgs/nixos-unstable;
   };
-  outputs = { self, flake-utils, nixpkgs, git-ignore-nix }:
+  outputs = { self, flake-utils, nixpkgs, unstable, git-ignore-nix }:
   let
-    overlay = final: prev: {
+    hpath = { prefix ? null, compiler ? null }:
-      haskellPackages = prev.haskellPackages.override (old: {
+      (if prefix == null then [] else [ prefix ]) ++
-        overrides = prev.lib.composeExtensions (old.overrides or (_: _: {}))
+      (if compiler == null
-        (hself: hsuper: {
+       then [ "haskellPackages" ]
-          xmonad = hself.callCabal2nix "xmonad" (git-ignore-nix.lib.gitignoreSource ./.) { };
+       else [ "haskell" "packages" compiler ]
-        });
+      );
-      });
+    fromHOL = hol: comp: final: prev: with prev.lib; with attrsets;
+      setAttrByPath (hpath comp)
+        ((getAttrFromPath (hpath comp) prev).override (old: {
+          overrides = composeExtensions (old.overrides or (_: _: {}))
+            (hol final prev);
+        }));
+    patch = unstable
+          + "/pkgs/development/haskell-modules/patches/xmonad_0_17_0-nix.patch";
+    hoverlay = final: prev: hself: hsuper:
+      with prev.haskell.lib.compose; {
+      xmonad = appendPatch patch
+        (hself.callCabal2nix "xmonad"
+          (git-ignore-nix.lib.gitignoreSource ./.) { });
       };
+    overlay = fromHOL hoverlay { };
     overlays = [ overlay ];
+    nixosModule = { config, pkgs, lib, ... }: with lib; with attrsets;
+      let
+        cfg = config.services.xserver.windowManager.xmonad.flake;
+        comp = { inherit (cfg) prefix compiler; };
+      in {
+        options = {
+          services.xserver.windowManager.xmonad.flake = with types; {
+            enable = mkEnableOption "flake";
+            prefix = mkOption {
+              default = null;
+              type = nullOr string;
+              example = literalExpression "\"unstable\"";
+              description = ''
+                Specify a nested alternative <literal>pkgs</literal> by attrName.
+              '';
+            };
+            compiler = mkOption {
+              default = null;
+              type = nullOr string;
+              example = literalExpression "\"ghc922\"";
+              description = ''
+                Which compiler to build xmonad with.
+                Must be an attribute of <literal>pkgs.haskell.packages</literal>.
+                Sets <option>xmonad.haskellPackages</option> to match.
+              '';
+            };
+          };
+        };
+        config = mkIf cfg.enable {
+          nixpkgs.overlays = [ (fromHOL hoverlay comp) ];
+          services.xserver.windowManager.xmonad.haskellPackages =
+            getAttrFromPath (hpath comp) pkgs;
+        };
+      };
+    nixosModules = [ nixosModule ];
   in flake-utils.lib.eachDefaultSystem (system:
   let pkgs = import nixpkgs { inherit system overlays; };
   in
@@ -23,5 +73,8 @@
       packages = p: [ p.xmonad ];
     };
     defaultPackage = pkgs.haskellPackages.xmonad;
-  }) // { inherit overlay overlays; } ;
+  }) // {
+    inherit hoverlay overlay overlays nixosModule nixosModules;
+    lib = { inherit hpath fromHOL; };
+  };
 }