lib/types: add types.{json,toml} from pkgs.formats

lib/types.nix

@@ -1437,6 +1437,45 @@ rec {
       };
     };
 
+  /**
+    Creates a value type suitable for serialization formats.
+
+    Parameters:
+    - typeName: String describing the format (e.g. "JSON", "YAML", "XML")
+    - nullable: Whether the structured value type allows `null` values.
+
+    Returns a type suitable for structured data formats that supports:
+    - Basic types: boolean, integer, float, string, path
+    - Complex types: attribute sets and lists
+  */
+  serializableValueWith =
+    {
+      typeName,
+      nullable ? true,
+    }:
+    let
+      baseType = oneOf [
+        bool
+        int
+        float
+        str
+        path
+        (attrsOf valueType)
+        (listOf valueType)
+      ];
+      valueType = (if nullable then nullOr baseType else baseType) // {
+        description = "${typeName} value";
+      };
+    in
+    valueType;
+
+  json = serializableValueWith { typeName = "JSON"; };
+
+  toml = serializableValueWith {
+    typeName = "TOML";
+    nullable = false;
+  };
+
   # Either value of type `t1` or `t2`.
   either =
     t1: t2:

nixos/doc/manual/development/option-types.section.md

@@ -497,6 +497,20 @@ Composed types are types that take a type as parameter. `listOf
     value of type *`to`*. Can be used to preserve backwards compatibility
     of an option if its type was changed.
 
+`types.json`
+
+:   A type representing JSON-compatible values. This includes `null`, booleans,
+    integers, floats, strings, paths, attribute sets, and lists.
+    Attribute sets and lists can be arbitrarily nested and contain any JSON-compatible
+    values.
+
+`types.toml`
+
+:   A type representing TOML-compatible values. This includes booleans,
+    integers, floats, strings, paths, attribute sets, and lists.
+    Attribute sets and lists can be arbitrarily nested and contain any TOML-compatible
+    values.
+
 ## Submodule {#section-option-types-submodule}
 
 `submodule` is a very powerful type that defines a set of sub-options

pkgs/pkgs-lib/formats.nix

@@ -40,6 +40,7 @@ let
     ;
 
   inherit (lib.types)
+    serializableValueWith
     attrsOf
     atom
     bool
@@ -58,38 +59,6 @@ let
     submodule
     ;
 
-  /*
-    Creates a structured value type suitable for serialization formats.
-
-    Parameters:
-    - typeName: String describing the format (e.g. "JSON", "YAML", "XML")
-    - nullable: Whether the structured value type allows `null` values.
-
-    Returns a type suitable for structured data formats that supports:
-    - Basic types: boolean, integer, float, string, path
-    - Complex types: attribute sets and lists
-  */
-  mkStructuredType =
-    {
-      typeName,
-      nullable ? true,
-    }:
-    let
-      baseType = oneOf [
-        bool
-        int
-        float
-        str
-        path
-        (attrsOf valueType)
-        (listOf valueType)
-      ];
-      valueType = (if nullable then nullOr baseType else baseType) // {
-        description = "${typeName} value";
-      };
-    in
-    valueType;
-
   # Attributes added accidentally in https://github.com/NixOS/nixpkgs/pull/335232 (2024-08-18)
   # Deprecated in https://github.com/NixOS/nixpkgs/pull/415666 (2025-06)
   allowAliases = pkgs.config.allowAliases or false;
@@ -162,7 +131,7 @@ optionalAttrs allowAliases aliases
     { }:
     {
 
-      type = mkStructuredType { typeName = "JSON"; };
+      type = types.json;
 
       generate =
         name: value:
@@ -203,7 +172,7 @@ optionalAttrs allowAliases aliases
             ''
         ) { };
 
-      type = mkStructuredType { typeName = "YAML 1.1"; };
+      type = serializableValueWith { typeName = "YAML 1.1"; };
 
     };
 
@@ -226,7 +195,7 @@ optionalAttrs allowAliases aliases
             ''
         ) { };
 
-      type = mkStructuredType { typeName = "YAML 1.2"; };
+      type = serializableValueWith { typeName = "YAML 1.2"; };
 
     };
 
@@ -487,10 +456,7 @@ optionalAttrs allowAliases aliases
     { }:
     json { }
     // {
-      type = mkStructuredType {
-        typeName = "TOML";
-        nullable = false;
-      };
+      type = types.toml;
 
       generate =
         name: value:
@@ -523,7 +489,7 @@ optionalAttrs allowAliases aliases
     { }:
     json { }
     // {
-      type = mkStructuredType { typeName = "CDN"; };
+      type = serializableValueWith { typeName = "CDN"; };
 
       generate =
         name: value:
@@ -938,7 +904,7 @@ optionalAttrs allowAliases aliases
   pythonVars =
     { }:
     {
-      type = attrsOf (mkStructuredType {
+      type = attrsOf (serializableValueWith {
         typeName = "Python";
       });
 
@@ -1020,7 +986,7 @@ optionalAttrs allowAliases aliases
     }:
     if format == "badgerfish" then
       {
-        type = mkStructuredType { typeName = "XML"; };
+        type = serializableValueWith { typeName = "XML"; };
 
         generate =
           name: value: