feat: add lib to flake outputs exposing multiService func

closes #25

flake.nix

@@ -7,6 +7,10 @@
       path = builtins.path { path = ./example; filter = path: _: baseNameOf path == "flake.nix"; };
     };
 
+    # NOTE: this is a lib factory, as it takes: { pkgs, lib }
+    # so before using we need to pass it to pkgs.callPackage
+    lib = import ./nix/lib.nix;
+
     # Config for https://github.com/srid/nixci
     # To run this, `nix run github:srid/nixci`
     nixci = let overrideInputs = { "services-flake" = ./.; }; in {

nix/default.nix

@@ -1,38 +1,7 @@
 { pkgs, lib, ... }:
 let
-  # Create an attrsOf module wrapper (`services.${name}`) around the given submodule.
-  #
-  # where module filename is of form `${name}.nix`. The submodule takes this
-  # 'name' parameter, and is expected to set the final process-compose config in
-  # its `outputs.settings` option.
-  multiService = mod:
-    let
-      # Derive name from filename
-      name = lib.pipe mod [
-        builtins.baseNameOf
-        (lib.strings.splitString ".")
-        builtins.head
-      ];
-    in
-    { config, ... }: {
-      options.services.${name} = lib.mkOption {
-        description = ''
-          ${name} service
-        '';
-        default = { };
-        type = lib.types.attrsOf (lib.types.submoduleWith {
-          specialArgs = { inherit pkgs; };
-          modules = [ mod ];
-        });
-      };
-      config.settings.imports =
-        lib.pipe config.services.${name} [
-          (lib.filterAttrs (_: cfg: cfg.enable))
-          (lib.mapAttrsToList (_: cfg: cfg.outputs.settings))
-        ];
-    };
-in
-{
+  inherit (import ./lib.nix { inherit pkgs lib; }) multiService;
+in {
   imports = builtins.map multiService [
     ./postgres.nix
     ./redis.nix

nix/lib.nix

@@ -0,0 +1,33 @@
+{ pkgs, lib ? pkgs.lib }: {
+  # Create an attrsOf module wrapper (`services.${name}`) around the given submodule.
+  #
+  # where module filename is of form `${name}.nix`. The submodule takes this
+  # 'name' parameter, and is expected to set the final process-compose config in
+  # its `outputs.settings` option.
+  multiService = mod:
+    let
+      # Derive name from filename
+      name = lib.pipe mod [
+        builtins.baseNameOf
+        (lib.strings.splitString ".")
+        builtins.head
+      ];
+    in
+    { config, ... }: {
+      options.services.${name} = lib.mkOption {
+        description = ''
+          ${name} service
+        '';
+        default = { };
+        type = lib.types.attrsOf (lib.types.submoduleWith {
+          specialArgs = { inherit pkgs; };
+          modules = [ mod ];
+        });
+      };
+      config.settings.imports =
+        lib.pipe config.services.${name} [
+          (lib.filterAttrs (_: cfg: cfg.enable))
+          (lib.mapAttrsToList (_: cfg: cfg.outputs.settings))
+        ];
+    };
+}