chore(nix): switch to flakes

Signed-off-by: Rudi Grinberg <[email protected]>

ps-id: 361819b3-0b29-43f8-b342-dabb9b17dec5

.gitignore

@@ -24,5 +24,6 @@ _perf
 dune.exe
 Makefile.dev
 src/dune_rules/setup.ml
+result
 
 .DS_Store

dune

@@ -1,3 +1,5 @@
+(dirs :standard \ result)
+
 (rule
  (copy dune-private-libs.opam.template dune-configurator.opam.template))
 

flake.nix

@@ -0,0 +1,56 @@
+{
+  inputs = {
+    opam-nix.url = "github:tweag/opam-nix";
+    flake-utils.url = "github:numtide/flake-utils";
+    ocamllsp.url = "git+https://github.com/ocaml/ocaml-lsp?submodules=1";
+    opam-nix.follows = "ocamllsp/opam-nix";
+    nixpkgs.follows = "ocamllsp/nixpkgs";
+  };
+  outputs = { self, flake-utils, opam-nix, nixpkgs, ocamllsp }@inputs:
+    let package = "dune";
+    in flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        devPackages = {
+          menhir = null;
+          lwt = null;
+          csexp = null;
+          core_bench = null;
+          bisect_ppx = null;
+          js_of_ocaml = null;
+          js_of_ocaml-compiler = null;
+          mdx = null;
+          merlin = null;
+          odoc = null;
+          ppx_expect = null;
+          ppxlib = null;
+          ctypes = null;
+          utop = null;
+          cinaps = null;
+          ocamlfind = "1.9.2";
+        };
+        on = opam-nix.lib.${system};
+      in {
+        legacyPackages = let
+          scope = on.buildOpamProject { } package ./. devPackages;
+          overlay = self: super: { };
+        in scope.overrideScope' overlay;
+
+        defaultPackage = self.legacyPackages.${system}.${package};
+
+        devShell = pkgs.mkShell {
+          nativeBuildInputs = let scope = self.legacyPackages.${system};
+          in with pkgs;
+          [
+            ocamllsp.outputs.defaultPackage.${system}
+            # dev tools
+            ocamlformat_0_21_0
+            opam
+            nodejs-slim
+            pkg-config
+          ] ++ (builtins.map (s: builtins.getAttr s scope)
+            (builtins.attrNames devPackages));
+          inputsFrom = [ self.defaultPackage.${system} ];
+        };
+      });
+}