in retrospect, just use submodule as the import

deployment/data-model.nix

@@ -15,7 +15,7 @@ let
     functionTo
     ;
 
-  functionType = import ./function.nix { inherit lib; };
+  functionType = submodule ./function.nix;
   application-resources = submodule {
     options.resources = mkOption {
       # TODO: maybe transpose, and group the resources by type instead

deployment/function.nix

@@ -1,7 +1,7 @@
 /**
   Modular function type
 */
-{ lib, ... }:
+{ config, lib, ... }:
 let
   inherit (lib) mkOption types;
   inherit (types)
@@ -10,9 +10,7 @@ let
     optionType
     ;
 in
-submodule (
-  { config, ... }:
-  {
+{
   options = {
     input-type = mkOption {
       type = optionType;
@@ -35,5 +33,4 @@ submodule (
       });
     };
   };
-  }
-)
+}