{
  inputs = {
    opam-nix.url = "github:tweag/opam-nix";
    flake-utils.url = "github:numtide/flake-utils";
    nixpkgs.follows = "opam-nix/nixpkgs";
  };
  outputs = { self, nixpkgs, flake-utils, opam-nix, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs { inherit system; };

        package = "sandy";
        on = opam-nix.lib.${system};
        localPackagesQuery = builtins.mapAttrs (_: pkgs.lib.last)
          (on.listRepo (on.makeOpamRepo ./.));
        devPackagesQuery = {
          earlybird = "*";
          ocaml-lsp-server = "*";
          ocamlformat = "*";
          utop = "*";
        };
        query = devPackagesQuery // {
          ocaml-base-compiler = "*";
        };
        scope = on.buildDuneProject { } package ./. query;
        overlay = final: prev:
          {
            # You can add overrides here
          };
        scope' = scope.overrideScope' overlay;
        # Packages from devPackagesQuery
        devPackages = builtins.attrValues
          (pkgs.lib.getAttrs (builtins.attrNames devPackagesQuery) scope');
        # Packages in this workspace
        packages =
          pkgs.lib.getAttrs (builtins.attrNames localPackagesQuery) scope';
      in {
        legacyPackages = scope';

        inherit packages;

        devShells.default = pkgs.mkShell {

          inputsFrom = builtins.attrValues packages;

          buildInputs = devPackages ++ [
            # You can add packages from nixpkgs here
          ];

          shellHook = ''
            echo "version = `ocamlformat --version`" > .ocamlformat
          '';
        };
      });
}