fix: In set_output_types check that the decorator @component.output_types is not present on the run_async method (#9485)

* Fix

* Add reno

haystack/core/component/component.py

@@ -512,13 +512,18 @@ class _Component:
             # no decorators here
             def run(self, value: int):
                 return {"output_1": 1, "output_2": "2"}
+
+            # also no decorators here
+            async def run_async(self, value: int):
+                return {"output_1": 1, "output_2": "2"}
         ```
         """
-        has_decorator = hasattr(instance.run, "_output_types_cache")
-        if has_decorator:
+        has_run_decorator = hasattr(instance.run, "_output_types_cache")
+        has_run_async_decorator = hasattr(instance, "run_async") and hasattr(instance.run_async, "_output_types_cache")
+        if has_run_decorator or has_run_async_decorator:
             raise ComponentError(
-                "Cannot call `set_output_types` on a component that already has "
-                "the 'output_types' decorator on its `run` method"
+                "Cannot call `set_output_types` on a component that already has the 'output_types' decorator on its "
+                "`run` or `run_async` methods."
             )
 
         instance.__haystack_output__ = Sockets(

releasenotes/notes/fix-set-output-types-async-check-2e5d578a3ccdcc59.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    When calling `set_output_types` we now also check that the decorator @component.output_types is not present on the `run_async` method of a Component. Previously we only checked that the Component.run method did not possess the decorator.

test/core/component/test_component.py

@@ -328,6 +328,23 @@ def test_output_types_decorator_and_set_output_types():
         _ = MockComponent()
 
 
+def test_output_types_decorator_and_set_output_types_async():
+    @component
+    class MockComponent:
+        def __init__(self) -> None:
+            component.set_output_types(self, value=int)
+
+        def run(self, value: int):
+            return {"value": 1}
+
+        @component.output_types(value=int)
+        async def run_async(self, value: int):
+            return {"value": 1}
+
+    with pytest.raises(ComponentError, match="Cannot call `set_output_types`"):
+        _ = MockComponent()
+
+
 def test_output_types_decorator_mismatch_run_async_run():
     @component
     class MockComponent: