Merge options having the submodule type.

Now we should be able to have multiple declaration of the same option as
long as all declarations have the same type.  If the type has a sub module,
then it is merged with the submodules of other declarations, as done with
option sets.

In addition, the file of the option declaration is passed into the
submodule, such as the documentation can display it correctly.

lib/modules.nix

@@ -144,7 +144,8 @@ rec {
          opt.options ? example && res ? example ||
          opt.options ? description && res ? description ||
          opt.options ? apply && res ? apply ||
-         opt.options ? type && res ? type
+         # Accept to merge options which have identical types.
+         opt.options ? type && res ? type && opt.options.type.name != res.type.name
       then
         throw "The option `${showOption loc}' in `${opt.file}' is already declared in ${showFiles res.declarations}."
       else
@@ -155,12 +156,16 @@ rec {
              current option declaration as the file use for the submodule.  If the
              submodule defines any filename, then we ignore the enclosing option file. */
           options' = toList opt.options.options;
+          addModuleFile = m:
+            if isFunction m then args: { _file = opt.file; } // (m args)
+            else { _file = opt.file; } // m;
           coerceOption = file: opt:
             if isFunction opt then args: { _file = file; } // (opt args)
-            else args: { _file = file; options = opt; };
+            else { _file = file; options = opt; };
+          getSubModules = opt.options.type.getSubModules or null;
           submodules =
-            if opt.options ? options
+            if getSubModules != null then map addModuleFile getSubModules ++ res.options
-            then map (coerceOption opt.file) options' ++ res.options
+            else if opt.options ? options then map (coerceOption opt.file) options' ++ res.options
             else res.options;
         in opt.options // res //
           { declarations = [opt.file] ++ res.declarations;
@@ -292,7 +297,8 @@ rec {
     in sort compare defs';
 
   /* Hack for backward compatibility: convert options of type
-     optionSet to configOf.  FIXME: remove eventually. */
+     optionSet to options of type submodule.  FIXME: remove
+     eventually. */
   fixupOptionType = loc: opt:
     let
       options = opt.options or
@@ -305,7 +311,10 @@ rec {
         else if tp.name == "list of option sets" then types.listOf (types.submodule options)
         else if tp.name == "null or option set" then types.nullOr (types.submodule options)
         else tp;
-    in opt // { type = f (opt.type or types.unspecified); };
+    in
+      if opt.type.getSubModules or null == null
+      then opt // { type = f (opt.type or types.unspecified); }
+      else opt // { type = opt.type.substSubModules opt.options; options = []; };
 
 
   /* Properties. */

lib/types.nix

@@ -33,9 +33,14 @@ rec {
     , # Return a flat list of sub-options.  Used to generate
       # documentation.
       getSubOptions ? prefix: {}
+    , # List of modules if any, or null if none.
+      getSubModules ? null
+    , # Function for building the same option type  with a different list of
+      # modules.
+      substSubModules ? m: null
     }:
     { _type = "option-type";
-      inherit name check merge getSubOptions;
+      inherit name check merge getSubOptions getSubModules substSubModules;
     };
 
 
@@ -110,6 +115,8 @@ rec {
           elemType.merge (loc ++ ["[${toString n}-${toString m}]"])
             [{ inherit (def) file; value = def'; }]) def.value) defs);
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["*"]);
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: listOf (elemType.substSubModules m);
     };
 
     attrsOf = elemType: mkOptionType {
@@ -121,6 +128,8 @@ rec {
           (map (def: listToAttrs (mapAttrsToList (n: def':
             { name = n; value = { inherit (def) file; value = def'; }; }) def.value)) defs);
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["<name>"]);
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: attrsOf (elemType.substSubModules m);
     };
 
     # List or attribute set of ...
@@ -147,12 +156,16 @@ rec {
           else false;
         merge = loc: defs: attrOnly.merge loc (imap convertIfList defs);
         getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["<name?>"]);
+        getSubModules = elemType.getSubModules;
+        substSubModules = m: loaOf (elemType.substSubModules m);
       };
 
     uniq = elemType: mkOptionType {
       inherit (elemType) name check;
       merge = mergeOneOption;
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: uniq (elemType.substSubModules m);
     };
 
     nullOr = elemType: mkOptionType {
@@ -165,6 +178,8 @@ rec {
           throw "The option `${showOption loc}' is defined both null and not null, in ${showFiles (getFiles defs)}."
         else elemType.merge loc defs;
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: nullOr (elemType.substSubModules m);
     };
 
     functionTo = elemType: mkOptionType {
@@ -173,6 +188,8 @@ rec {
       merge = loc: defs:
         fnArgs: elemType.merge loc (map (fn: { inherit (fn) file; value = fn.value fnArgs; }) defs);
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: functionTo (elemType.substSubModules m);
     };
 
     submodule = opts:
@@ -192,6 +209,8 @@ rec {
           { modules = opts'; inherit prefix;
             # FIXME: hack to get shit to evaluate.
             args = { name = ""; }; }).options;
+        getSubModules = opts';
+        substSubModules = m: submodule m;
       };
 
     enum = values: mkOptionType {