Address PR feedback: Fix ForwardRef issues, improve error messages, enhance docs

Co-Authored-By: Joe Moura <joao@crewai.com>

examples/task_decomposition_example.py

@@ -0,0 +1,47 @@
+"""
+Example of using task decomposition in CrewAI.
+
+This example demonstrates how to use the task decomposition feature
+to break down complex tasks into simpler sub-tasks.
+
+Feature introduced in CrewAI v1.x.x
+"""
+
+from crewai import Agent, Task, Crew
+
+researcher = Agent(
+    role="Researcher",
+    goal="Research effectively",
+    backstory="You're an expert researcher with skills in breaking down complex topics.",
+)
+
+research_task = Task(
+    description="Research the impact of AI on various industries",
+    expected_output="A comprehensive report covering multiple industries",
+    agent=researcher,
+)
+
+sub_tasks = research_task.decompose(
+    descriptions=[
+        "Research AI impact on healthcare industry",
+        "Research AI impact on finance industry",
+        "Research AI impact on education industry",
+    ],
+    expected_outputs=[
+        "A report on AI in healthcare",
+        "A report on AI in finance",
+        "A report on AI in education",
+    ],
+    names=["Healthcare", "Finance", "Education"],
+)
+
+crew = Crew(
+    agents=[researcher],
+    tasks=[research_task],
+)
+
+result = crew.kickoff()
+print("Final result:", result)
+
+for i, sub_task in enumerate(research_task.sub_tasks):
+    print(f"Sub-task {i+1} result: {sub_task.output.raw if hasattr(sub_task, 'output') and sub_task.output else 'No output'}")

src/crewai/task.py

@@ -19,6 +19,7 @@ from typing import (
     Tuple,
     Type,
     Union,
+    ForwardRef,
 )
 
 from opentelemetry.trace import Span
@@ -137,6 +138,16 @@ class Task(BaseModel):
         default=0,
         description="Current number of retries"
     )
+    parent_task: Optional['Task'] = Field(
+        default=None,
+        description="Parent task that this task was decomposed from.",
+        exclude=True,
+    )
+    sub_tasks: List['Task'] = Field(
+        default_factory=list,
+        description="Sub-tasks that this task was decomposed into.",
+        exclude=True,
+    )
 
     @field_validator("guardrail")
     @classmethod
@@ -246,13 +257,151 @@ class Task(BaseModel):
             )
         return self
 
+    def decompose(
+        self,
+        descriptions: List[str],
+        expected_outputs: Optional[List[str]] = None,
+        names: Optional[List[str]] = None
+    ) -> List['Task']:
+        """
+        Decompose a complex task into simpler sub-tasks.
+        
+        Args:
+            descriptions: List of descriptions for each sub-task.
+            expected_outputs: Optional list of expected outputs for each sub-task.
+            names: Optional list of names for each sub-task.
+            
+        Returns:
+            List of created sub-tasks.
+            
+        Raises:
+            ValueError: If descriptions is empty, or if expected_outputs or names
+                       have different lengths than descriptions.
+                       
+        Side Effects:
+            Modifies self.sub_tasks by adding newly created sub-tasks.
+        """
+        if not descriptions:
+            raise ValueError("At least one sub-task description is required.")
+            
+        if expected_outputs and len(expected_outputs) != len(descriptions):
+            raise ValueError(
+                f"If provided, expected_outputs must have the same length as descriptions. "
+                f"Got {len(expected_outputs)} expected outputs and {len(descriptions)} descriptions."
+            )
+            
+        if names and len(names) != len(descriptions):
+            raise ValueError(
+                f"If provided, names must have the same length as descriptions. "
+                f"Got {len(names)} names and {len(descriptions)} descriptions."
+            )
+            
+        for i, description in enumerate(descriptions):
+            sub_task = Task(
+                description=description,
+                expected_output=expected_outputs[i] if expected_outputs else self.expected_output,
+                name=names[i] if names else None,
+                agent=self.agent,  # Inherit the agent from the parent task
+                tools=self.tools,  # Inherit the tools from the parent task
+                context=[self],    # Set the parent task as context for the sub-task
+                parent_task=self,  # Reference back to the parent task
+            )
+            self.sub_tasks.append(sub_task)
+            
+        return self.sub_tasks
+        
+    def combine_sub_task_results(self) -> str:
+        """
+        Combine the results from all sub-tasks into a single result for this task.
+        
+        This method uses the task's agent to intelligently combine the results from
+        all sub-tasks. It requires an agent capable of coherent text summarization
+        and is designed for stateless prompt execution.
+        
+        Returns:
+            The combined result as a string.
+            
+        Raises:
+            ValueError: If the task has no sub-tasks or no agent assigned.
+            
+        Side Effects:
+            None. This method does not modify the task's state.
+        """
+        if not self.sub_tasks:
+            raise ValueError("Task has no sub-tasks to combine results from.")
+            
+        if not self.agent:
+            raise ValueError("Task has no agent to combine sub-task results.")
+            
+        sub_task_results = "\n\n".join([
+            f"Sub-task: {sub_task.description}\nResult: {sub_task.output.raw if sub_task.output else 'No result'}"
+            for sub_task in self.sub_tasks
+        ])
+        
+        combine_prompt = f"""
+        You have completed the following sub-tasks for the main task: "{self.description}"
+        
+        {sub_task_results}
+        
+        Based on all these sub-tasks, please provide a consolidated final answer for the main task.
+        Expected output format: {self.expected_output if self.expected_output else 'Not specified'}
+        """
+        
+        result = self.agent.execute_task(
+            task=self,
+            context=combine_prompt,
+            tools=self.tools or []
+        )
+        
+        return result
+    
     def execute_sync(
         self,
         agent: Optional[BaseAgent] = None,
         context: Optional[str] = None,
         tools: Optional[List[BaseTool]] = None,
     ) -> TaskOutput:
-        """Execute the task synchronously."""
+        """
+        Execute the task synchronously.
+        
+        If the task has sub-tasks and no output yet, this method will:
+        1. Execute all sub-tasks first
+        2. Combine their results using the agent
+        3. Set the combined result as this task's output
+        
+        Args:
+            agent: Optional agent to execute the task with.
+            context: Optional context to pass to the task.
+            tools: Optional tools to pass to the task.
+            
+        Returns:
+            TaskOutput: The result of the task execution.
+            
+        Side Effects:
+            Sets self.output with the execution result.
+        """
+        if self.sub_tasks and not self.output:
+            for sub_task in self.sub_tasks:
+                sub_task.execute_sync(
+                    agent=sub_task.agent or agent,
+                    context=context,
+                    tools=sub_task.tools or tools or [],
+                )
+            
+            # Combine the results from sub-tasks
+            result = self.combine_sub_task_results()
+            
+            self.output = TaskOutput(
+                description=self.description,
+                name=self.name,
+                expected_output=self.expected_output,
+                raw=result,
+                agent=self.agent.role if self.agent else None,
+                output_format=self.output_format,
+            )
+            
+            return self.output
+        
         return self._execute_core(agent, context, tools)
 
     @property
@@ -278,6 +427,55 @@ class Task(BaseModel):
         ).start()
         return future
 
+    def execute_sub_tasks_async(
+        self,
+        agent: Optional[BaseAgent] = None,
+        context: Optional[str] = None,
+        tools: Optional[List[BaseTool]] = None,
+    ) -> List[Future[TaskOutput]]:
+        """
+        Execute all sub-tasks asynchronously.
+        
+        This method starts the execution of all sub-tasks in parallel and returns
+        futures that can be awaited. After all futures are complete, you should call
+        combine_sub_task_results() to aggregate the results.
+        
+        Example:
+            ```python
+            futures = task.execute_sub_tasks_async()
+            
+            for future in futures:
+                future.result()
+                
+            # Combine the results
+            result = task.combine_sub_task_results()
+            ```
+        
+        Args:
+            agent: Optional agent to execute the sub-tasks with.
+            context: Optional context to pass to the sub-tasks.
+            tools: Optional tools to pass to the sub-tasks.
+            
+        Returns:
+            List of futures for the sub-task executions.
+            
+        Raises:
+            ValueError: If the task has no sub-tasks.
+        """
+        if not self.sub_tasks:
+            return []
+            
+        futures = []
+        for sub_task in self.sub_tasks:
+            future = sub_task.execute_async(
+                agent=sub_task.agent or agent,
+                context=context,
+                tools=sub_task.tools or tools or [],
+            )
+            futures.append(future)
+            
+        return futures
+        
     def _execute_task_async(
         self,
         agent: Optional[BaseAgent],
@@ -434,6 +632,8 @@ class Task(BaseModel):
             "agent",
             "context",
             "tools",
+            "parent_task",
+            "sub_tasks",
         }
 
         copied_data = self.model_dump(exclude=exclude)
@@ -457,6 +657,7 @@ class Task(BaseModel):
             agent=cloned_agent,
             tools=cloned_tools,
         )
+        
 
         return copied_task
 
@@ -526,3 +727,6 @@ class Task(BaseModel):
 
     def __repr__(self):
         return f"Task(description={self.description}, expected_output={self.expected_output})"
+
+
+Task.model_rebuild()

tests/test_task_decomposition.py

@@ -0,0 +1,157 @@
+import pytest
+from unittest.mock import Mock, patch
+
+from crewai import Agent, Task
+
+
+def test_task_decomposition_structure():
+    """Test that task decomposition creates the proper parent-child relationship."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI on various industries",
+        expected_output="A comprehensive report",
+        agent=agent,
+    )
+    
+    sub_task_descriptions = [
+        "Research AI impact on healthcare",
+        "Research AI impact on finance",
+        "Research AI impact on education",
+    ]
+    
+    sub_tasks = parent_task.decompose(
+        descriptions=sub_task_descriptions,
+        expected_outputs=["Healthcare report", "Finance report", "Education report"],
+        names=["Healthcare", "Finance", "Education"],
+    )
+    
+    assert len(sub_tasks) == 3
+    assert len(parent_task.sub_tasks) == 3
+    
+    for sub_task in sub_tasks:
+        assert sub_task.parent_task == parent_task
+        assert parent_task in sub_task.context
+
+
+def test_task_execution_with_sub_tasks():
+    """Test that executing a task with sub-tasks executes the sub-tasks first."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI on various industries",
+        expected_output="A comprehensive report",
+        agent=agent,
+    )
+    
+    sub_task_descriptions = [
+        "Research AI impact on healthcare",
+        "Research AI impact on finance",
+        "Research AI impact on education",
+    ]
+    
+    parent_task.decompose(
+        descriptions=sub_task_descriptions,
+        expected_outputs=["Healthcare report", "Finance report", "Education report"],
+    )
+    
+    with patch.object(Agent, 'execute_task', return_value="Mock result") as mock_execute_task:
+        result = parent_task.execute_sync()
+        
+        assert mock_execute_task.call_count >= 3
+        
+        for sub_task in parent_task.sub_tasks:
+            assert sub_task.output is not None
+        
+        assert result is not None
+        assert result.raw is not None
+
+
+def test_combine_sub_task_results():
+    """Test that combining sub-task results works correctly."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI on various industries",
+        expected_output="A comprehensive report",
+        agent=agent,
+    )
+    
+    sub_tasks = parent_task.decompose([
+        "Research AI impact on healthcare",
+        "Research AI impact on finance",
+    ])
+    
+    for sub_task in sub_tasks:
+        sub_task.output = Mock()
+        sub_task.output.raw = f"Result for {sub_task.description}"
+    
+    with patch.object(Agent, 'execute_task', return_value="Combined result") as mock_execute_task:
+        result = parent_task.combine_sub_task_results()
+        
+        assert mock_execute_task.called
+        assert result == "Combined result"
+
+
+def test_task_decomposition_validation():
+    """Test that task decomposition validates inputs correctly."""
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+    )
+    
+    with pytest.raises(ValueError, match="At least one sub-task description is required"):
+        parent_task.decompose([])
+    
+    with pytest.raises(ValueError, match="expected_outputs must have the same length"):
+        parent_task.decompose(
+            ["Task 1", "Task 2"], 
+            expected_outputs=["Output 1"]
+        )
+    
+    with pytest.raises(ValueError, match="names must have the same length"):
+        parent_task.decompose(
+            ["Task 1", "Task 2"], 
+            names=["Name 1"]
+        )
+
+
+def test_execute_sub_tasks_async():
+    """Test that executing sub-tasks asynchronously works correctly."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI on various industries",
+        expected_output="A comprehensive report",
+        agent=agent,
+    )
+    
+    sub_tasks = parent_task.decompose([
+        "Research AI impact on healthcare",
+        "Research AI impact on finance",
+    ])
+    
+    with patch.object(Task, 'execute_async') as mock_execute_async:
+        mock_future = Mock()
+        mock_execute_async.return_value = mock_future
+        
+        futures = parent_task.execute_sub_tasks_async()
+        
+        assert mock_execute_async.call_count == 2
+        assert len(futures) == 2

tests/test_task_decomposition_edge_cases.py

@@ -0,0 +1,109 @@
+import pytest
+from unittest.mock import Mock, patch
+
+from crewai import Agent, Task, TaskOutput
+
+
+def test_combine_sub_task_results_no_sub_tasks():
+    """Test that combining sub-task results raises an error when there are no sub-tasks."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+        agent=agent,
+    )
+    
+    with pytest.raises(ValueError, match="Task has no sub-tasks to combine results from"):
+        parent_task.combine_sub_task_results()
+
+
+def test_combine_sub_task_results_no_agent():
+    """Test that combining sub-task results raises an error when there is no agent."""
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+    )
+    
+    sub_task = Task(
+        description="Research AI impact on healthcare",
+        expected_output="Healthcare report",
+        parent_task=parent_task,
+    )
+    parent_task.sub_tasks.append(sub_task)
+    
+    with pytest.raises(ValueError, match="Task has no agent to combine sub-task results"):
+        parent_task.combine_sub_task_results()
+
+
+def test_execute_sync_sets_output_after_combining():
+    """Test that execute_sync sets the output after combining sub-task results."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+        agent=agent,
+    )
+    
+    sub_tasks = parent_task.decompose([
+        "Research AI impact on healthcare",
+        "Research AI impact on finance",
+    ])
+    
+    with patch.object(Agent, 'execute_task', return_value="Combined result") as mock_execute_task:
+        result = parent_task.execute_sync()
+        
+        assert parent_task.output is not None
+        assert parent_task.output.raw == "Combined result"
+        assert result.raw == "Combined result"
+        
+        assert mock_execute_task.call_count >= 3
+
+
+def test_deep_cloning_prevents_shared_state():
+    """Test that deep cloning prevents shared mutable state between tasks."""
+    agent = Agent(
+        role="Researcher",
+        goal="Research effectively",
+        backstory="You're an expert researcher",
+    )
+    
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+        agent=agent,
+    )
+    
+    copied_task = parent_task.copy()
+    
+    copied_task.description = "Modified description"
+    
+    assert parent_task.description == "Research the impact of AI"
+    assert copied_task.description == "Modified description"
+    
+    parent_task.decompose(["Sub-task 1", "Sub-task 2"])
+    
+    assert len(parent_task.sub_tasks) == 2
+    assert len(copied_task.sub_tasks) == 0
+
+
+def test_execute_sub_tasks_async_empty_sub_tasks():
+    """Test that execute_sub_tasks_async returns an empty list when there are no sub-tasks."""
+    parent_task = Task(
+        description="Research the impact of AI",
+        expected_output="A report",
+    )
+    
+    futures = parent_task.execute_sub_tasks_async()
+    
+    assert isinstance(futures, list)
+    assert len(futures) == 0