Add Nix support for reproducible build and develop

.envrc

@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+
+use flake

.gitattributes

@@ -1,2 +1,4 @@
 # Auto detect text files and perform LF normalization
 * text=auto
+
+flake.lock linguist-generated=true

.gitignore

@@ -4,7 +4,7 @@
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
-Cargo.lock
+# Cargo.lock
 
 # These are backup files generated by rustfmt
 **/*.rs.bk
@@ -15,4 +15,8 @@ Cargo.lock
 /.DS_Store
 /*/.DS_Store
 /.idea/
-/timeit.dat
+/timeit.dat
+
+# Nix
+.direnv
+result

README.md

@@ -172,6 +172,24 @@ Building from source code requires the Rust toolchain.
 git clone https://github.com/erg-lang/erg.git
 cd erg
 cargo build --release
+``` 
+
+### Building by Nix
+
+If you've been installed [Nix](https://nixos.org/), the following command will be generate binary into `result/bin/erg` under the project.
+
+```sh
+git clone https://github.com/erg-lang/erg.git
+cd erg
+nix-build
+```
+
+If you've been enabled [Nix Flakes](https://nixos.wiki/wiki/Flakes). 
+
+```sh
+git clone https://github.com/erg-lang/erg.git
+cd erg
+nix build
 ```
 
 ## Contribution

README_JA.md

@@ -172,6 +172,24 @@ cd erg
 cargo build --release
 ```
 
+### Nixによるビルド
+
+[Nix](https://nixos.org/)をインストールしているなら，次のコマンドでプロジェクト直下の`result/bin/erg`にバイナリが生成されます．
+
+```sh
+git clone https://github.com/erg-lang/erg.git
+cd erg
+nix-build
+```
+
+[Nix Flakes](https://nixos.wiki/wiki/Flakes)を有効化している場合は次のコマンドでも良いです. 
+
+```sh
+git clone https://github.com/erg-lang/erg.git
+cd erg
+nix build
+```
+
 ## コントリビューション
 
 コントリビューション(プロジェクトへの貢献、協力)はいつでも歓迎しています！

default.nix

@@ -0,0 +1,12 @@
+(
+  import
+  (
+    fetchTarball
+    (with (builtins.fromJSON (builtins.readFile ./flake.lock)).nodes.flake-compat.locked; {
+      url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+      sha256 = narHash;
+    })
+  )
+  {src = ./.;}
+)
+.defaultNix

flake.nix

@@ -0,0 +1,67 @@
+{
+  description = "Nix Flake for Erg Programming Language";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+    # develop
+    devshell.url = "github:numtide/devshell";
+    flake-utils.url = "github:numtide/flake-utils";
+    flake-compat = {
+      url = "github:edolstra/flake-compat";
+      flake = false;
+    };
+  };
+  outputs = {
+    self,
+    nixpkgs,
+    devshell,
+    flake-utils,
+    ...
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [
+            devshell.overlay
+          ];
+        };
+        cargoToml = with builtins; (fromTOML (readFile ./Cargo.toml));
+
+        inherit (pkgs) lib;
+      in {
+        packages.erg = pkgs.rustPlatform.buildRustPackage {
+          inherit (cargoToml.package) name version;
+          src = builtins.path {
+            path = ./.;
+            filter = name: type:
+              (name == toString ./Cargo.toml)
+              || (name == toString ./Cargo.lock)
+              || (lib.hasPrefix (toString ./compiler) name)
+              || (lib.hasPrefix (toString ./src) name);
+          };
+          cargoLock.lockFile = ./Cargo.lock;
+        };
+        packages.default = self.packages.${system}.erg;
+
+        devShells.default = pkgs.devshell.mkShell {
+          packages = with pkgs; [
+            gcc
+            rustc
+            cargo
+            # Dev
+            python3
+            treefmt # cli to run all formatters
+            alejandra # Nix formatter
+            # rustfmt # Rust Formatter
+            # taplo-cli # TOML formatter
+          ];
+        };
+
+        checks = {
+          erg = self.packages.${system}.erg;
+        };
+      }
+    );
+}

shell.nix

@@ -0,0 +1,12 @@
+(
+  import
+  (
+    fetchTarball
+    (with (builtins.fromJSON (builtins.readFile ./flake.lock)).nodes.flake-compat.locked; {
+      url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+      sha256 = narHash;
+    })
+  )
+  {src = ./.;}
+)
+.shellNix

treefmt.toml

@@ -0,0 +1,12 @@
+[formatter.alejandra]
+command = "alejandra"
+includes = ["*.nix"]
+
+# [formatter.taplo]
+# command = "taplo"
+# options = ["format"]
+# includes = ["*.toml"]
+
+# [formatter.rustfmt]
+# command = "rustfmt"
+# includes = ["*.rs"]