Add devbox support

Author: alex35mil

CONTRIBUTING.md

@@ -75,7 +75,7 @@ Build PPX:
 esy build
 ```
 
-**Nix flow**
+**Nix/Devbox flow**
 Build PPX:
 
 ```shell

devbox.json

@@ -0,0 +1,20 @@
+{
+    "packages": [
+        "path:./nix/ocaml#ocaml",
+        "path:./nix/ocaml#dune",
+        "path:./nix/ocaml#reason",
+        "path:./nix/ocaml#result",
+        "path:./nix/ocaml#findlib",
+        "path:./nix/ocaml#ppxlib",
+        "path:./nix/ocaml#alcotest",
+        "path:./nix/ocaml#merlin",
+        "path:./nix/ocaml#lsp",
+        "nodejs",
+        "yarn"
+    ],
+    "shell": {
+        "init_hook": [
+            "export PATH=$PATH:node_modules/.bin"
+        ]
+    }
+}

devbox.lock

@@ -0,0 +1,22 @@
+{
+  "lockfile_version": "1",
+  "packages": {
+    "nodejs": {
+      "resolved": "github:NixOS/nixpkgs/f80ac848e3d6f0c12c52758c0f25c10c97ca3b62#nodejs",
+      "source": "nixpkg"
+    },
+    "path:./nix/ocaml#alcotest": {},
+    "path:./nix/ocaml#dune": {},
+    "path:./nix/ocaml#findlib": {},
+    "path:./nix/ocaml#lsp": {},
+    "path:./nix/ocaml#merlin": {},
+    "path:./nix/ocaml#ocaml": {},
+    "path:./nix/ocaml#ppxlib": {},
+    "path:./nix/ocaml#reason": {},
+    "path:./nix/ocaml#result": {},
+    "yarn": {
+      "resolved": "github:NixOS/nixpkgs/f80ac848e3d6f0c12c52758c0f25c10c97ca3b62#yarn",
+      "source": "nixpkg"
+    }
+  }
+}

nix/ocaml/flake.lock

@@ -0,0 +1,50 @@
+{
+    description = "OCaml 4.12 packages for ReScript PPX development";
+
+    inputs = {
+        nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+        flake-utils.url = "github:numtide/flake-utils";
+    };
+
+    outputs = { self, nixpkgs, flake-utils }:
+        flake-utils.lib.eachDefaultSystem (system:
+            let
+                overlay = (final: prev: {
+                    ocaml-ng = prev.ocaml-ng // {
+                        ocamlPackages_4_12 = prev.ocaml-ng.ocamlPackages_4_12 // {
+                            ppxlib = prev.ocaml-ng.ocamlPackages_4_12.ppxlib.overrideAttrs (_: {
+                                version = "git";
+                                src = pkgs.fetchFromGitHub {
+                                    owner = "zth";
+                                    repo = "ppxlib";
+                                    rev = "32f83395fb89693a873541298b6367449f23bc4a";
+                                    sha256 = "sha256-8bkmeFh5Unda8n3F2MQWi81QPt2NdkwFcy4wZTJ0STo=";
+                                };
+                                patches = [];
+                            });
+                        };
+                    };
+                });
+
+                pkgs = import nixpkgs {
+                    inherit system;
+                    overlays = [ overlay ];
+                };
+
+                ocamlPackages = pkgs.ocaml-ng.ocamlPackages_4_12;
+            in
+            {
+                packages = {
+                    ocaml = ocamlPackages.ocaml;
+                    dune = ocamlPackages.dune_3;
+                    reason = ocamlPackages.reason;
+                    result = ocamlPackages.result;
+                    findlib = ocamlPackages.findlib;
+                    ppxlib = ocamlPackages.ppxlib;
+                    alcotest = ocamlPackages.alcotest;
+                    merlin = ocamlPackages.merlin;
+                    lsp = ocamlPackages.ocaml-lsp;
+                };
+            }
+        );
+}