Support wildcard handling in emit() (#2424)

* Support wildcard handling in `emit()`

Change `emit()` to call handlers registered for parent classes using
`isinstance()`. Ensures that base event handlers receive derived
events.

* Fix failing test

* Remove unused variable

src/crewai/utilities/events/crewai_event_bus.py

@@ -67,15 +67,12 @@ class CrewAIEventsBus:
             source: The object emitting the event
             event: The event instance to emit
         """
-        event_type = type(event)
-        if event_type in self._handlers:
-            for handler in self._handlers[event_type]:
-                handler(source, event)
-        self._signal.send(source, event=event)
+        for event_type, handlers in self._handlers.items():
+            if isinstance(event, event_type):
+                for handler in handlers:
+                    handler(source, event)
 
-    def clear_handlers(self) -> None:
-        """Clear all registered event handlers - useful for testing"""
-        self._handlers.clear()
+        self._signal.send(source, event=event)
 
     def register_handler(
         self, event_type: Type[EventTypes], handler: Callable[[Any, EventTypes], None]

tests/utilities/events/test_crewai_event_bus.py

@@ -0,0 +1,34 @@
+from unittest.mock import Mock
+
+from crewai.utilities.events.base_events import CrewEvent
+from crewai.utilities.events.crewai_event_bus import crewai_event_bus
+
+
+class TestEvent(CrewEvent):
+    pass
+
+
+def test_specific_event_handler():
+    mock_handler = Mock()
+
+    @crewai_event_bus.on(TestEvent)
+    def handler(source, event):
+        mock_handler(source, event)
+
+    event = TestEvent(type="test_event")
+    crewai_event_bus.emit("source_object", event)
+
+    mock_handler.assert_called_once_with("source_object", event)
+
+
+def test_wildcard_event_handler():
+    mock_handler = Mock()
+
+    @crewai_event_bus.on(CrewEvent)
+    def handler(source, event):
+        mock_handler(source, event)
+
+    event = TestEvent(type="test_event")
+    crewai_event_bus.emit("source_object", event)
+
+    mock_handler.assert_called_once_with("source_object", event)