From dae33d4e94a1dc145d34c690fdd95c8de0f3df69 Mon Sep 17 00:00:00 2001
From: Antonio Nuno Monteiro <anmonteiro@gmail.com>
Date: Sat, 7 Dec 2024 17:57:09 -0800
Subject: [PATCH] nix: remove flake-utils in favor of lib.genAttrs (#1244)

---
 flake.lock | 48 ++++++-----------------------------
 flake.nix  | 73 +++++++++++++++++++++++++++++-------------------------
 2 files changed, 46 insertions(+), 75 deletions(-)

diff --git a/flake.lock b/flake.lock
index f30483499..9f44c669f 100644
--- a/flake.lock
+++ b/flake.lock
@@ -1,23 +1,5 @@
 {
   "nodes": {
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1731533236,
-        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "melange-compiler-libs": {
       "inputs": {
         "nixpkgs": [
@@ -58,11 +40,11 @@
         "nixpkgs": "nixpkgs_2"
       },
       "locked": {
-        "lastModified": 1733004991,
-        "narHash": "sha256-MpK4wT/Qn+kINWu2yMli20yJMKfEuarKu9b248Om6SA=",
+        "lastModified": 1733618663,
+        "narHash": "sha256-InGcpprb28501vo7POwnTk/Pbi8Co5gbpxfkdzofQRk=",
         "owner": "nix-ocaml",
         "repo": "nix-overlays",
-        "rev": "198a22a3eab0361a0e1e349e798397f6f3f0464c",
+        "rev": "82ac3f123030e98f63baf95ad9841cc152a362aa",
         "type": "github"
       },
       "original": {
@@ -73,42 +55,26 @@
     },
     "nixpkgs_2": {
       "locked": {
-        "lastModified": 1732951447,
-        "narHash": "sha256-ndq0dD5E6FkqwmNYFS1wUAHa/5HixS3jLjulogM+7/E=",
+        "lastModified": 1733603762,
+        "narHash": "sha256-E+cuaL8s1oHCumWD/Zkw0gkLOOQcz848pVyLfvqWDVw=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "57feb2a16f705eeffb075888d92a986e66473012",
+        "rev": "b1dd465e8139748a8e26037fdd4c5ffe79457cbd",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "57feb2a16f705eeffb075888d92a986e66473012",
+        "rev": "b1dd465e8139748a8e26037fdd4c5ffe79457cbd",
         "type": "github"
       }
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
         "melange-compiler-libs": "melange-compiler-libs",
         "nix-filter": "nix-filter",
         "nixpkgs": "nixpkgs"
       }
-    },
-    "systems": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
     }
   },
   "root": "root",
diff --git a/flake.nix b/flake.nix
index 0f2aaa2bb..21f20c545 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,58 +3,63 @@
 
   inputs = {
     nix-filter.url = "github:numtide/nix-filter";
-    flake-utils.url = "github:numtide/flake-utils";
-    nixpkgs = {
-      url = "github:nix-ocaml/nix-overlays";
-      inputs.flake-utils.follows = "flake-utils";
-    };
+    nixpkgs.url = "github:nix-ocaml/nix-overlays";
     melange-compiler-libs = {
       # this changes rarely, and it's better than having to rely on nix's poor
       # support for submodules
       url = "github:melange-re/melange-compiler-libs";
-      inputs.flake-utils.follows = "flake-utils";
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
 
-  outputs = { self, nixpkgs, flake-utils, nix-filter, melange-compiler-libs }:
+  outputs = { self, nixpkgs, nix-filter, melange-compiler-libs }:
+    let
+      forAllSystems = f: nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system}.extend (self: super: {
+            ocamlPackages = super.ocaml-ng.ocamlPackages_5_3;
+          });
+        in
+        f pkgs);
+    in
     {
       overlays.default = import ./nix/overlay.nix {
         nix-filter = nix-filter.lib;
         melange-compiler-libs-vendor-dir = melange-compiler-libs;
       };
-    } // (flake-utils.lib.eachDefaultSystem (system:
-      let
-        pkgs = nixpkgs.legacyPackages."${system}".extend (self: super: {
-          ocamlPackages = super.ocaml-ng.ocamlPackages_5_3;
-        });
 
-        packages =
-          let
-            melange = pkgs.callPackage ./nix {
-              nix-filter = nix-filter.lib;
-              melange-compiler-libs-vendor-dir = melange-compiler-libs;
-            };
-          in
-          {
+      packages = forAllSystems (pkgs:
+        let
+          melange = pkgs.callPackage ./nix {
+            nix-filter = nix-filter.lib;
+            melange-compiler-libs-vendor-dir = melange-compiler-libs;
+          };
+        in
+        {
+          inherit melange;
+          default = melange;
+          melange-playground = pkgs.ocamlPackages.callPackage ./nix/melange-playground.nix {
             inherit melange;
-            default = melange;
-            melange-playground = pkgs.ocamlPackages.callPackage ./nix/melange-playground.nix {
-              inherit melange;
-              nix-filter = nix-filter.lib;
-              melange-compiler-libs-vendor-dir = melange-compiler-libs;
-            };
+            nix-filter = nix-filter.lib;
+            melange-compiler-libs-vendor-dir = melange-compiler-libs;
           };
-        melange-shell = opts:
-          pkgs.callPackage ./nix/shell.nix ({ inherit packages; } // opts);
-      in
-      {
-        inherit packages;
-        devShells = {
+        }
+      );
+
+      devShells = forAllSystems (pkgs:
+        let
+          melange-shell = opts:
+            pkgs.callPackage ./nix/shell.nix ({
+              packages = self.packages.${pkgs.system};
+            } // opts);
+
+        in
+        {
           default = melange-shell { };
           release = melange-shell {
             release-mode = true;
           };
-        };
-      }));
+        }
+      );
+    };
 }