nix

flake.nix

@@ -1,42 +1,82 @@
 {
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    haskellNix.url = "github:input-output-hk/haskell.nix";
+    # nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    nixpkgs.follows = "haskellNix/nixpkgs-unstable";
   };
 
-  outputs = { self, nixpkgs, ... }@inputs:
+  outputs = { self, nixpkgs, haskellNix, ... }@inputs:
     let
       supportedSystems = [
         "aarch64-darwin" "aarch64-linux"
         "x86_64-darwin" "x86_64-linux"
       ];
 
+      overlays = [
+        haskellNix.overlay
+        (final: _prev: {
+          # This overlay adds our project to pkgs
+          qbe-hs = final.haskell-nix.project' {
+            src = ./.;
+            compiler-nix-name = "ghc912";
+            # This is used by `nix develop .` to open a shell for use with
+            # `cabal`, `hlint` and `haskell-language-server`
+            shell.tools = {
+              cabal = {};
+              # hlint = {};
+              # haskell-language-server = {};
+            };
+            # Non-Haskell shell tools go here
+            shell.buildInputs = with final; [
+              gcc
+              qbe
+            ];
+            # passthru = { inherit (final) qbe; };
+            # This adds `js-unknown-ghcjs-cabal` to the shell.
+            # shell.crossPlatforms = p: [p.ghcjs];
+          };
+        })
+      ];
+
       each-system = f: nixpkgs.lib.genAttrs supportedSystems (system: f rec {
 	pkgs = import nixpkgs {
-          inherit system;
+          inherit system overlays;
         };
 	inherit (pkgs) lib;
         inherit system;
       });
+
+      # haskell-flake
+      hf =
+        let
+          keys = [
+            "packages" "apps" "devShells"
+            "hydraJobs" "ciJobs" "checks"
+          ];
+        in nixpkgs.lib.genAttrs keys
+          (k: each-system ({ pkgs, ... }: (pkgs.qbe-hs.flake {}).${k}));
     in {
       # Exposed as a REPL convenience.
       _pkgs = each-system ({ pkgs, ... }: pkgs);
 
-      packages = each-system ({ pkgs, ... }: {
-        # default = pkgs.callPackage ./default.nix {};
-      });
+      packages = each-system ({ pkgs, system, ... }:
+        hf.packages.${system} // {
+          default = hf.packages.${system}."qbe:lib:qbe";
+        });
 
-      devShells = each-system ({ pkgs, system, ... }: {
-	default = pkgs.haskellPackages.developPackage {
-          root = ./.;
-          modifier = drv:
-            pkgs.haskell.lib.addBuildTools
-              drv
-              (with pkgs; [
-                cabal-install
-                qbe
-                gcc
-              ]);
-	};
-      });
+      devShells = each-system
+        ({ pkgs, system, ... }: hf.devShells.${system});
     };
+
+  nixConfig = {
+    extra-substituters = [
+      "https://cache.iog.io"
+      "https://cache.zw3rk.com"
+    ];
+    extra-trusted-public-keys = [
+      "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="
+      "loony-tools:pr9m4BkM/5/eSTZlkQyRt57Jz7OMBxNSUiMC4FkcNfk="
+    ];
+    allow-import-from-derivation = "true";
+  };
 }