dragnpkgs/flake.nix

{
  description = "dragnpkgs together with nixpkgs and lix";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.11";

    lix-module = {
      url = "https://git.lix.systems/lix-project/nixos-module/archive/2.91.1-2.tar.gz";
      flake = false;
    };

    lix = {
      url = "https://git.lix.systems/lix-project/lix/archive/2.91.1.tar.gz";
      flake = false;
    };
  };

  outputs = { self, nixpkgs, lix, lix-module }:
    let
      overlays = [
        (import ./overlay.nix)
        (import "${lix-module}/overlay.nix" { inherit lix; })
      ];
      forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
    in {
      # we don't just use nix.registry.whatever.flake = self
      # the reason for this is to be able to handle a flake.lock containing an entry for this
      # flake -- setting .flake makes it a path entry in the registry, whereas we want our
      # self reference in the registry to be downloadable by URL in case it makes it into a
      # flake.lock
      meta.registry-entry = {
        from = { id = "dragnpkgs"; type = "indirect"; };
        to = {
          type = "git";
          url = "https://git.lain.faith/haskal/dragnpkgs.git";
          ref = "nixos-24.11";
        } // self.lib.filterAttrs
          (n: _: n == "lastModified" || n == "rev" || n == "revCount" || n == "narHash")
          self;
      };

      # the nix path entry for self
      meta.path-entry = "dragnpkgs=flake:dragnpkgs";

      lib = nixpkgs.lib.extend (final: prev: {
        nixosSystem = args:
          import "${nixpkgs}/nixos/lib/eval-config.nix" (
            {
              lib = final;

              system = null;

              modules = args.modules ++ [
                ({ config, pkgs, lib, ... }: {
                  config.nixpkgs = {
                    # we remove nixpkgs' machinery for setting self flake references and
                    # replace it with our own (in the next inline module)
                    flake = {
                      source = self.outPath;
                      setNixPath = false;
                      setFlakeRegistry = false;
                    };

                    overlays = overlays;
                  };

                  # this is in the flake rather than in module.nix so there's still control over
                  # channels if you're not using a flake based config. but for flake based
                  # configs, we're not doing channels anymore
                  config.nix = {
                    channel.enable = false;
                  };
                })

                ({ options, config, pkgs, lib, ...}: {
                  options.dragnpkgs = {
                    setFlakeRegistry = lib.mkOption {
                      description = "Set flake registry option pointing to self";
                      type = lib.types.bool;
                      default = true;
                      defaultText = lib.literalExpression "true";
                      example = lib.literalExpression "false";
                    };

                    setNixPath = lib.mkOption {
                      description = "Set nix path entry pointing to self";
                      type = lib.types.bool;
                      default = true;
                      defaultText = lib.literalExpression "true";
                      example = lib.literalExpression "false";
                    };

                    setNixpkgsFlakeAlias = lib.mkOption {
                      description = "Set nix path entry for `nixpkgs` to self";
                      type = lib.types.bool;
                      default = true;
                      defaultText = lib.literalExpression "true";
                      example = lib.literalExpression "false";
                    };
                  };

                  config.nix.registry.dragnpkgs = lib.mkIf config.dragnpkgs.setFlakeRegistry self.meta.registry-entry;
                  config.nix.registry.nixpkgs = lib.mkIf config.dragnpkgs.setNixpkgsFlakeAlias {
                    from = { id = "nixpkgs"; type = "indirect"; };
                    to = { id = "dragnpkgs"; type = "indirect"; };
                  };

                  config.nix.nixPath = lib.mkIf config.dragnpkgs.setNixPath [
                    self.meta.path-entry
                  ];
                })

                (import ./module.nix)
              ];
            } // builtins.removeAttrs args [ "modules" ]
          );

        mkFlake = flakeDef:
          let
            rewritePerSystem = sectionDef: (forAllSystems (system:
              builtins.mapAttrs (name: value:
                if final.isDerivation value then
                  value
                else
                  self.legacyPackages.${system}.callPackage value {}
              ) sectionDef
            ));
          in
            builtins.mapAttrs (name: value:
              if name == "packages" || name == "legacyPackages" || name == "devShells" then
                rewritePerSystem value
              else
                value
            ) flakeDef;
      });

      legacyPackages = forAllSystems (system:
        nixpkgs.legacyPackages.${system}.appendOverlays overlays
      );

      nixosModules = nixpkgs.nixosModules;
    };
}