doctrine/lib: support module dependencies

doctrine/lib/mk-module.nix

@@ -1,12 +1,14 @@
 {
+  # The first few arguments are implicitly passed by the 'close' helper
+  lib,
+  pkgs,
+  doctrine,
   name,
+  config,
   hm ? null,
   sys ? null,
   options ? null,
-  lib,
+  requires ? [],
-  config,
-  pkgs,
-  doctrine,
 }: let
   optionsSet = import options {
     inherit config lib pkgs cfg name doctrine;
@@ -24,7 +26,17 @@
 in {
   config =
     lib.optionalAttrs (configFiles ? ${doctrine.namespace})
-    (lib.mkIf cfg.enable configSet);
+    (lib.mkIf cfg.enable (lib.mkMerge [
+      configSet
+      {
+        assertions =
+          map (dependency: {
+            assertion = cfg.enable -> config.${doctrine.prefix}.${dependency}.enable;
+            message = "${doctrine.prefix}.${name}.enable requires ${doctrine.prefix}.${dependency}.enable";
+          })
+          requires;
+      }
+    ]));
 
   options.${doctrine.prefix}.${name} =
     lib.optionalAttrs (options != null && optionsSet ? ${doctrine.namespace}) optionsSet.${doctrine.namespace}