build node_modules without breaking chroot

.gitignore

@@ -1,3 +1,4 @@
 .next/
 node_modules/
 out/
+result

flake.nix

@@ -21,26 +21,45 @@
 
       nodejs = pkgs.nodejs-18_x;
 
-      node_modules = pkgs.stdenv.mkDerivation {
+      src = filter {
-        name = "node_modules";
+        root = ./.;
+        include = [
+          ./package.json
+          ./package-lock.json
+        ];
+      };
 
-        src = filter {
+      # Read lockfile
-          root = ./.;
+      packageLock = builtins.fromJSON(builtins.readFile (src + "/package-lock.json"));
-          include = [
+
-            ./package.json
+      # Convert to tarball dep list
-            ./package-lock.json
+      deps = builtins.attrValues (removeAttrs packageLock.packages [ "" ])
-          ];
+        ++ builtins.attrValues (removeAttrs (packageLock.dependencies or {} ) [ "" ])
-        };
+      ;
+      tarballs = map (p: pkgs.fetchurl { url = p.resolved; hash = p.integrity; }) deps;
+      tarballsFile = pkgs.writeTextFile {
+        name = "tarballs";
+        text = builtins.concatStringsSep "\n" tarballs;
+      };
 
-        __noChroot = true;
+      # build npm cache
+      ashenearth_modules = pkgs.stdenv.mkDerivation {
+        inherit src;
 
-        configurePhase = ''
+        name = "node_modules";
-          export HOME=$TMP
-        '';
 
         buildInputs = [ nodejs ];
 
         buildPhase = ''
+          export HOME=$PWD/.home
+          export npm_config_cache=$PWD/.npm
+
+          while read package
+          do
+            echo "caching $(echo $package | sed 's/\/nix\/store\/[^-]*-//')"
+            npm cache add "$package"
+          done <${tarballsFile}
+
           ${nodejs}/bin/npm ci
         '';
 
@@ -70,7 +89,7 @@
           '';
 
           configurePhase = ''
-            ln -sf ${node_modules}/node_modules node_modules
+            ln -sf ${ashenearth_modules}/node_modules node_modules
             export HOME=$TMP
           '';