types: improve dagOf and listOrDagOf

In particular, improve the behavior of these types if the element type
is a submodule.

modules/lib/types-dag.nix

@@ -7,16 +7,25 @@ let
   isDagEntry = e: isAttrs e && (e ? data) && (e ? after) && (e ? before);
 
   dagContentType = elemType:
-    types.submodule {
+    types.submodule ({ name, ... }: {
       options = {
         data = mkOption { type = elemType; };
         after = mkOption { type = with types; uniq (listOf str); };
         before = mkOption { type = with types; uniq (listOf str); };
       };
-    };
+      config = mkIf (elemType.name == "submodule") {
+        data._module.args.dagName = name;
+      };
+    });
 
-in {
+in rec {
   # A directed acyclic graph of some inner type.
+  #
+  # Note, if the element type is a submodule then the `name` argument
+  # will always be set to the string "data" since it picks up the
+  # internal structure of the DAG values. To give access to the
+  # "actual" attribute name a new submodule argument is provided with
+  # the name `dagName`.
   dagOf = elemType:
     let
       convertAllToDags = let
@@ -51,34 +60,30 @@ in {
         let padWidth = stringLength (toString (length list));
         in fixedWidthNumber padWidth i;
 
-      convertAllToDags = defs:
+      convertAll = defs:
         let
-          convertAttrValue = n: v:
-            if isDagEntry v then v else dag.entryAnywhere v;
-
           convertListValue = namePrefix: vs:
             let
               pad = paddedIndexStr vs;
-              makeEntry = i: v:
-                nameValuePair "${namePrefix}.${pad i}" (dag.entryAnywhere v);
+              makeEntry = i: v: nameValuePair "${namePrefix}.${pad i}" v;
             in listToAttrs (imap1 makeEntry vs);
 
           convertValue = i: value:
             if isList value then
               convertListValue "unnamed-${paddedIndexStr defs i}" value
             else
-              mapAttrs convertAttrValue value;
+              value;
         in imap1 (i: def: def // { value = convertValue i def.value; }) defs;
 
-      attrEquivalent = types.attrsOf (dagContentType elemType);
+      dagType = dagOf elemType;
     in mkOptionType rec {
-      name = "dagOf";
-      description = "DAG of ${elemType.description}s";
-      check = x: isAttrs x || isList x;
-      merge = loc: defs: attrEquivalent.merge loc (convertAllToDags defs);
-      getSubOptions = prefix: elemType.getSubOptions (prefix ++ [ "<name>" ]);
-      getSubModules = elemType.getSubModules;
-      substSubModules = m: dagOf (elemType.substSubModules m);
+      name = "listOrDagOf";
+      description = "list or DAG of ${elemType.description}s";
+      check = x: isList x || dagType.check x;
+      merge = loc: defs: dagType.merge loc (convertAll defs);
+      getSubOptions = dagType.getSubOptions;
+      getSubModules = dagType.getSubModules;
+      substSubModules = m: listOrDagOf (elemType.substSubModules m);
       functor = (defaultFunctor name) // { wrapped = elemType; };
     };
 }

tests/lib/types/dag-submodule.nix

@@ -0,0 +1,43 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  dag = config.lib.dag;
+
+  result = let
+    sorted = dag.topoSort config.tested.dag;
+    data = map (e: "${e.name}:${e.data.name}") sorted.result;
+  in concatStringsSep "\n" data + "\n";
+
+in {
+  options.tested.dag = mkOption {
+    type = hm.types.dagOf (types.submodule ({ dagName, ... }: {
+      options.name = mkOption { type = types.str; };
+      config.name = "dn-${dagName}";
+    }));
+  };
+
+  config = {
+    tested.dag = {
+      after = { };
+      before = dag.entryBefore [ "after" ] { };
+      between = dag.entryBetween [ "after" ] [ "before" ] { };
+    };
+
+    home.file."result.txt".text = result;
+
+    nmt.script = ''
+      assertFileContent \
+        home-files/result.txt \
+        ${
+          pkgs.writeText "result.txt" ''
+            before:dn-before
+            between:dn-between
+            after:dn-after
+          ''
+        }
+    '';
+  };
+}

tests/lib/types/default.nix

@@ -1,4 +1,5 @@
 {
+  lib-types-dag-submodule = ./dag-submodule.nix;
   lib-types-dag-merge = ./dag-merge.nix;
   lib-types-list-or-dag-merge = ./list-or-dag-merge.nix;