Add flake-utils

flake.lock

@@ -1,5 +1,23 @@
 {
   "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"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1752536923,
@@ -18,8 +36,24 @@
     },
     "root": {
       "inputs": {
+        "flake-utils": "flake-utils",
         "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",

flake.nix

@@ -2,11 +2,11 @@
   description = "An opionated Postgres library";
 
   inputs.nixpkgs.url = "github:nixos/nixpkgs/release-25.05";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  outputs = { self, nixpkgs }:
+  outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system:
     let
-      system = "aarch64-darwin";
-      pkgs = nixpkgs.legacyPackages.${system};
+      pkgs = import nixpkgs { inherit system; };
       opium = pkgs.haskellPackages.developPackage {
         root = ./.;
         modifier = drv:
@@ -17,12 +17,13 @@
           ];
       };
     in {
-      packages.${system}.opium = pkgs.haskell.lib.overrideCabal opium {
+      packages.opium = pkgs.haskell.lib.overrideCabal opium {
         # Currently the tests require a running Postgres instance.
         # This is not automated yet, so don't export the tests.
         doCheck = false;
       };
 
-      devShells.${system}.default = opium.env;
-    };
+      devShells.default = opium.env;
+    }
+  );
 }