add the thing formally

src/wf_authoring/nodes/result.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from typing import Generic, TypeVar
+from typing import Generic, TypeVar, overload
 
 from pydantic import BaseModel
 
@@ -14,3 +14,25 @@ class NodeReturn(Generic[OutputT_co]):
 
     outcome: str
     output: OutputT_co
+
+
+class Nothing(BaseModel):
+    """Empty output model for nodes that only choose an outcome."""
+
+
+@overload
+def outcome(name: str) -> NodeReturn[Nothing]: ...
+
+
+@overload
+def outcome(name: str, output: OutputT_co) -> NodeReturn[OutputT_co]: ...
+
+
+def outcome(
+    name: str,
+    output: OutputT_co | None = None,
+) -> NodeReturn[OutputT_co] | NodeReturn[Nothing]:
+    """Create a node result with an optional output model."""
+    if output is None:
+        return NodeReturn(outcome=name, output=Nothing())
+    return NodeReturn(outcome=name, output=output)