Add nixd.

Add nixd to flake.nix and legacyPackages.nix.

Format with alejandra.

flake.nix

@@ -9,10 +9,14 @@
     # inputs is used to get the original standard library, and to pass inputs to the plugin autodiscovery function
     lib = import ./lib/stdlib-extended.nix inputs;
   in
-    flake-parts.lib.mkFlake {
+    flake-parts.lib.mkFlake
+    {
       inherit inputs;
-      specialArgs = {inherit lib;};
-    } {
+      specialArgs = {
+        inherit lib;
+      };
+    }
+    {
       # Allow users to bring their own systems.
       # «https://github.com/nix-systems/nix-systems»
       systems = import inputs.systems;
@@ -66,7 +70,12 @@
           default = self'.devShells.lsp;
           nvim-nix = pkgs.mkShell {packages = [config.packages.nix];};
           lsp = pkgs.mkShell {
-            packages = with pkgs; [nil statix deadnix alejandra];
+            packages = with pkgs; [
+              nil
+              statix
+              deadnix
+              alejandra
+            ];
           };
         };
 
@@ -111,6 +120,10 @@
       inputs.nixpkgs.follows = "nixpkgs";
       inputs.flake-utils.follows = "flake-utils";
     };
+    nixd = {
+      url = "github:nix-community/nixd";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
 
     ## Plugins
     # LSP plugins

flake/legacyPackages.nix

@@ -11,6 +11,7 @@
         (_: _: {
           rnix-lsp = inputs'.rnix-lsp.defaultPackage;
           nil = inputs'.nil.packages.default;
+          nixd = inputs'.nixd.packages.default;
         })
       ];
     };

modules/plugins/languages/nix.nix

@@ -74,6 +74,22 @@
         }
       '';
     };
+
+    nixd = {
+      package = pkgs.nixd;
+      internalFormatter = cfg.format.type == "nixpkgs-fmt";
+      lspConfig = ''
+        lspconfig.nixd.setup{
+          capabilities = capabilities,
+        ${
+          if (cfg.format.enable && cfg.format.type == "nixpkgs-fmt")
+          then useFormat
+          else noFormat
+        },
+          cmd = ${packageToCmd cfg.lsp.package "nixd"},
+        }
+      '';
+    };
   };
 
   defaultFormat = "alejandra";