chore: DRY calls

Author: davidnbr

flake.nix

@@ -25,7 +25,8 @@
         "aarch64-darwin"
       ];
 
-      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f system);
+      # nixpkgs.lib.genAttrs already takes a list and a function — no wrapper needed.
+      forAllSystems = nixpkgs.lib.genAttrs systems;
 
       lib = rec {
         inherit versionMap;
@@ -61,40 +62,45 @@
               }
           else
             throw "Node.js version ${version} not found in versionMap";
-
-        getNodejs =
-          { system, version }:
-          let
-            pkgs = getNixpkgs { inherit system version; };
-            attrName = versionMap.${version}.attr or "nodejs";
-            attrPath = nixpkgs.lib.splitString "." attrName;
-          in
-          nixpkgs.lib.attrByPath attrPath (throw "Attribute ${attrName} not found") pkgs;
       };
 
       packagesForSystem =
         system:
         let
           pkgs = nixpkgs.legacyPackages.${system};
 
-          basePackages = builtins.mapAttrs (
-            version: versionInfo: lib.getNodejs { inherit system version; }
+          # Import each pinned nixpkgs exactly once per version.
+          # All package sets below (base, yarn, pnpm) read from this map,
+          # so getNixpkgs is never called more than once per version per system.
+          perVersionPkgs = builtins.mapAttrs (
+            version: _: lib.getNixpkgs { inherit system version; }
           ) versionMap;
 
+          basePackages = builtins.mapAttrs (
+            version: versionPkgs:
+            let
+              attrName = versionMap.${version}.attr or "nodejs";
+              attrPath = nixpkgs.lib.splitString "." attrName;
+            in
+            nixpkgs.lib.attrByPath attrPath (throw "Attribute ${attrName} not found") versionPkgs
+          ) perVersionPkgs;
+
           # Create aliases like nodejs_20_18 for 20.18
           aliases = nixpkgs.lib.mapAttrs' (
             version: pkg:
             nixpkgs.lib.nameValuePair ("nodejs_" + (builtins.replaceStrings [ "." ] [ "_" ] version)) pkg
           ) basePackages;
 
-          # Create yarn packages bundled with the specific node version
+          # Create yarn packages bundled with the specific node version.
           # Uses the version-pinned nixpkgs to ensure yarn/node compatibility
           # (e.g. Node 16 gets yarn 1.x, avoiding OpenSSL/API mismatches with newer yarn).
           # Falls back to latest nixpkgs if yarn is absent from the pinned rev.
+          # yarn has consistently accepted a nodejs override argument across all nixpkgs
+          # versions in the supported range, so no __functionArgs guard is needed here.
           yarnPackages = nixpkgs.lib.mapAttrs' (
             version: pkg:
             let
-              versionPkgs = lib.getNixpkgs { inherit system version; };
+              versionPkgs = perVersionPkgs.${version};
               yarnPkgs = if builtins.hasAttr "yarn" versionPkgs then versionPkgs else pkgs;
             in
             nixpkgs.lib.nameValuePair ("yarn_" + (builtins.replaceStrings [ "." ] [ "_" ] version)) (
@@ -110,26 +116,29 @@
 
           # Create pnpm packages bundled with the specific node version.
           # Strategy: use the pnpm that ships in the same pinned nixpkgs as the Node
-          # version
+          # version — it is already era-compatible (e.g. pnpm 8 with Node 18.16).
           #
           # Older nixpkgs keep pnpm under nodePackages.pnpm; newer ones promote it to
-          # pkgs.pnpm with a callable-attrset override that accepts a nodejs argument.
-          # When that override is available we thread
+          # pkgs.pnpm with a callable-attrset override that accepts a nodejs argument
+          # (detectable via .__functionArgs). When that override is available we thread
           # our exact Node derivation through it; otherwise we use pnpm as-is.
           #
           # Falls back to latest nixpkgs pnpm only when the pinned rev has no pnpm at
           # all (rare, but guards against evaluation errors).
           pnpmPackages = nixpkgs.lib.mapAttrs' (
             version: pkg:
             let
-              versionPkgs = lib.getNixpkgs { inherit system version; };
+              versionPkgs = perVersionPkgs.${version};
 
+              # Prefer top-level pkgs.pnpm (pnpm 10+ era); fall back to nodePackages.pnpm
               pinnedPnpm =
                 if builtins.hasAttr "pnpm" versionPkgs then
                   versionPkgs.pnpm
                 else
                   versionPkgs.nodePackages.pnpm or null;
 
+              # In newer nixpkgs pnpm.override is a callable attrset whose __functionArgs
+              # mirror the original package function — check for nodejs there.
               pnpmOverride = if builtins.isNull pinnedPnpm then null else pinnedPnpm.override or null;
               canOverrideNodejs =
                 builtins.isAttrs pnpmOverride
@@ -158,22 +167,24 @@
         basePackages // aliases // yarnPackages // pnpmPackages;
     in
     {
+      # Standard Flake Outputs
       packages = forAllSystems (
         system:
-        (packagesForSystem system)
-        // {
-          # Default to latest LTS (22.22)
-          default = (packagesForSystem system)."22.22";
-        }
+        let
+          allPkgs = packagesForSystem system;
+        in
+        allPkgs // { default = allPkgs."22.22"; }
       );
 
+      # Overlay allows users to use these packages in their own nixpkgs instance
       overlays.default =
         final: prev:
         let
           pkgsForSystem = packagesForSystem final.system;
         in
         pkgsForSystem;
 
+      # Formatter for the project
       formatter = forAllSystems (system: nixpkgs.legacyPackages.${system}.nixpkgs-fmt);
 
       # Library functions for integration (compatible with asdf2nix API)