Add comments about the module system interface

Ideally the module system could be configured pretty much completely by
the contents of the modules themselves, so add comments about avoiding
complicating it further and possibly removing now-redundant
configurability from the existing interface.

1 files changed, 14 insertions, 2 deletions

diff --git a/lib/modules.nix b/lib/modules.nix
index 1d7c7b22765e..26193b269410 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -9,8 +9,19 @@ rec {
 
   /* Evaluate a set of modules.  The result is a set of two
      attributes: ‘options’: the nested set of all option declarations,
-     and ‘config’: the nested set of all option values. */
-  evalModules = { modules, prefix ? [], args ? {}, check ? true }:
+     and ‘config’: the nested set of all option values.
+     !!! Please think twice before adding to this argument list! The more
+     that is specified here instead of in the modules themselves the harder
+     it is to transparently move a set of modules to be a submodule of another
+     config (as the proper arguments need to be replicated at each call to
+     evalModules) and the less declarative the module set is. */
+  evalModules = { modules
+                , prefix ? []
+                , # !!! This can be specified modularly now, can we remove it?
+                  args ? {}
+                , # !!! This can be specified modularly now, can we remove it?
+                  check ? true
+                }:
     let
       internalModule = rec {
         _file = ./modules.nix;
@@ -21,6 +32,7 @@ rec {
           __internal.args = mkOption {
             description = "Arguments passed to each module.";
 
+            # !!! Should this be types.uniq types.unspecified?
             type = types.attrsOf types.unspecified;
 
             internal = true;