Configure NixOS development environment for Lichess

* Read Node version from .node-version for single source of truth
* Use dart-sass instead of embedded to avoid NixOS dynamic linking issues
* Add Redis to dev dependencies
* Set SASS_PATH to use system dart-sass via SASS_PATH env var
* Update shellHook with LD_LIBRARY_PATH for NixOS compatibility

flake.lock

@@ -2,12 +2,12 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1771848320,
-        "narHash": "sha256-0MAd+0mun3K/Ns8JATeHT1sX28faLII5hVLq0L3BdZU=",
-        "rev": "2fc6539b481e1d2569f25f8799236694180c0993",
-        "revCount": 953160,
+        "lastModified": 1775423009,
+        "narHash": "sha256-vPKLpjhIVWdDrfiUM8atW6YkIggCEKdSAlJPzzhkQlw=",
+        "rev": "68d8aa3d661f0e6bd5862291b5bb263b2a6595c9",
+        "revCount": 975402,
         "type": "tarball",
-        "url": "https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.953160%2Brev-2fc6539b481e1d2569f25f8799236694180c0993/019c8e05-d2f6-7c7e-9ead-612154b18bfb/source.tar.gz"
+        "url": "https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.975402%2Brev-68d8aa3d661f0e6bd5862291b5bb263b2a6595c9/019d657b-b3b7-7288-b3c0-42d420df206b/source.tar.gz"
       },
       "original": {
         "type": "tarball",

flake.nix

@@ -8,6 +8,9 @@
 
     let
       javaVersion = 21;
+      # Source of truth for Node version is .node-version
+      nodeVersionFile = builtins.readFile ./.node-version;
+      nodeMajorVersion = builtins.elemAt (inputs.nixpkgs.lib.strings.split "\\." (builtins.replaceStrings [ "v" ] [ "" ] nodeVersionFile)) 0;
       supportedSystems = [
         "x86_64-linux"
         "aarch64-linux"
@@ -37,8 +40,8 @@
           sbt = prev.sbt.override { jre = jdk; };
           scala = prev.scala_3.override { jre = jdk; };
 
-          nodejs_24 = prev.nodejs_24;
-          pnpm = (prev.pnpm.override { nodejs = prev.nodejs_24; });
+          nodejs = prev."nodejs_${nodeMajorVersion}";
+          pnpm = (prev.pnpm.override { inherit nodejs; });
 
           esbuild = prev.esbuild.overrideAttrs (previousAttrs: rec {
             version = "0.25.11";
@@ -56,9 +59,10 @@
         {
           default = pkgs.mkShellNoCC {
             packages = with pkgs; [
-              nodejs_24
-              nodePackages.pnpm
+              nodejs
+              pnpm
               esbuild
+              dart-sass
               oxlint
               oxfmt
               stylelint
@@ -67,7 +71,16 @@
               scala
               sbt
               coursier
+
+              mongosh
+              redis
             ];
+            # Required for NixOS to run prebuilt binaries from npm packages
+            shellHook = ''
+              export LD_LIBRARY_PATH=${pkgs.lib.makeLibraryPath [ pkgs.stdenv.cc.cc ]}:$LD_LIBRARY_PATH
+              # Use dart-sass instead of npm's sass-embedded
+              export SASS_PATH=${pkgs.dart-sass}/bin/sass
+            '';
           };
         }
       );