snow-cli test

nix/snow/modules/default.nix

@@ -0,0 +1,5 @@
+{...}: {
+  imports = [
+    ./outputs.nix
+  ];
+}

nix/snow/modules/outputs.nix

@@ -0,0 +1,37 @@
+{lib, ...}: let
+  inherit
+    (lib)
+    mkOption
+    types
+    ;
+in {
+  options = {
+    outputs = mkOption {
+      type = types.submoduleWith {
+        modules = [
+          {
+            freeformType =
+              types.lazyAttrsOf
+              (types.unique
+                {
+                  message = ''
+                    No option has been declared for this flake output attribute, so its definitions can't be merged automatically.
+                    Possible solutions:
+                      - Load a module that defines this flake output attribute
+                      - Declare an option for this flake output attribute
+                      - Make sure the output attribute is spelled correctly
+                      - Define the value only once, with a single definition in a single module
+                  '';
+                }
+                types.raw);
+          }
+        ];
+      };
+      description = ''
+        Raw flake output attributes. Any attribute can be set here, but some
+        attributes are represented by options, to provide appropriate
+        configuration merging.
+      '';
+    };
+  };
+}