feat(devShells): shell for nix language

.envrc

@@ -0,0 +1 @@
+use flake .#nix

devShells/default.nix

@@ -3,7 +3,7 @@
 /**
   Isolated environments for convenient software development.
   Provides shells for all languages I use:
-  - ~~❄️  [Nix]~~  (not yet)
+  - ❄️  [Nix](./devShells/nix.md)
   - ~~🦀 Rust~~  (not yet)
   - ~~🐍 Python~~  (not yet)
 

devShells/nix/.envrc

@@ -0,0 +1 @@
+use flake

devShells/nix/default.nix

@@ -0,0 +1,20 @@
+# Nix
+/**
+  Basic shell for nix-only projects.
+  Many nix projects have their own devshell,
+  but they don't install most necessary tools.
+*/
+pkgs: rec {
+  /**
+    nix language server
+  */
+  packages.nixd = pkgs.nixd;
+  /**
+    nix formatter
+  */
+  packages.nixfmt = pkgs.nixfmt;
+  /**
+    nix linter
+  */
+  packages.statix = pkgs.statix;
+}

devShells/nix/flake.nix

@@ -0,0 +1,25 @@
+{
+  description = "Development shell for nix projects";
+
+  inputs.nixpkgs = "github:nixos/nixpkgs";
+  inputs.utils = "github:numtide/flake-utils";
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      utils,
+    }:
+    utils.lib.eachDefaultSystem (
+      sys:
+      let
+        pkgs = nixpkgs.legacyPackages.${sys};
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          name = "nix";
+          packages = map (p: p) (builtins.attrValues (import ./. pkgs).packages);
+        };
+      }
+    );
+}