adding task callback

src/crewai/task.py

@@ -15,19 +15,22 @@ class Task(BaseModel):
     __hash__ = object.__hash__  # type: ignore
     i18n: I18N = I18N()
     description: str = Field(description="Description of the actual task.")
-    agent: Optional[Agent] = Field(
-        description="Agent responsible for the task.", default=None
+    callback: Optional[Any] = Field(
+        description="Callback to be executed after the task is completed.", default=None
     )
-    tools: List[Any] = Field(
-        default_factory=list,
-        description="Tools the agent is limited to use for this task.",
+    agent: Optional[Agent] = Field(
+        description="Agent responsible for executiong the task.", default=None
     )
-    expected_output: str = Field(
+    expected_output: Optional[str] = Field(
         description="Clear definition of expected output for the task.",
         default=None,
     )
     output: Optional[TaskOutput] = Field(
-        description="Task output, it's final result.", default=None
+        description="Task output, it's final result after being executed", default=None
+    )
+    tools: List[Any] = Field(
+        default_factory=list,
+        description="Tools the agent is limited to use for this task.",
     )
     id: UUID4 = Field(
         default_factory=uuid.uuid4,
@@ -66,6 +69,7 @@ def execute(self, context: Optional[str] = None) -> str:
         )
 
         self.output = TaskOutput(description=self.description, result=result)
+        self.callback(self.output) if self.callback else None
         return result
 
     def _prompt(self) -> str:

tests/task_test.py

@@ -75,3 +75,31 @@ def test_task_prompt_includes_expected_output():
         execute.return_value = "ok"
         task.execute()
         execute.assert_called_once_with(task=task._prompt(), context=None, tools=[])
+
+
+def test_task_callback():
+    from unittest.mock import MagicMock
+
+    researcher = Agent(
+        role="Researcher",
+        goal="Make the best research and analysis on content about AI and AI agents",
+        backstory="You're an expert researcher, specialized in technology, software engineering, AI and startups. You work as a freelancer and is now working on doing research and analysis for a new customer.",
+        allow_delegation=False,
+    )
+
+    task_completed = MagicMock(return_value="done")
+
+    task = Task(
+        description="Give me a list of 5 interesting ideas to explore for na article, what makes them unique and interesting.",
+        expected_output="Bullet point list of 5 interesting ideas.",
+        agent=researcher,
+        callback=task_completed,
+        allow_delegation=False,
+    )
+
+    from unittest.mock import patch
+
+    with patch.object(Agent, "execute_task") as execute:
+        execute.return_value = "ok"
+        task.execute()
+        task_completed.assert_called_once_with(task.output)