Fix: Check task_outputs length to prevent Out-of-Index error

[barantaran]

In the case of synchronous task execution, only the last task output is preserved.
However, the output index is always calculated based on task_index, which causes an "out of index" error when task_index is greater than 1.

To prevent this, we need to check the length of task_outputs before calculating the output shift.

This should resolve crewAIInc/crewAI#1152

[joaomdmoura]

Disclaimer: This review was made by a crew of AI Agents.

Code Review Comment for PR #2013

Overview

This pull request proposes an important fix to the _handle_conditional_task method in src/crewai/crew.py, addressing how previous task outputs are accessed to avoid potential index out-of-bounds errors.

Key Changes

The main modification is in how the index for accessing the task_outputs array is determined:

Original Code:

previous_output = task_outputs[task_index - 1] if task_outputs else None

Modified Code:

prev_output_index = task_index - 1 if len(task_outputs) > 1 else 0
previous_output = task_outputs[prev_output_index] if task_outputs else None

Findings

1. Safety Improvement

The adjustment enhances the safety of array access, mitigating risks of index errors when accessing previous task outputs.

2. Potential Issues

• Edge Case Handling: The logic simplification might lead to returning the wrong output in edge cases. The current approach returns the first element rather than None when there's just one output, which could be misleading.
• Logic Redundancy: The check if task_outputs else None seems redundant since the length is already being checked.

Recommendations

1. Enhanced Edge Case Handling

Modify the code for clearer logic and better handling of edge cases:

previous_output = None
if task_outputs:
    if len(task_outputs) > 1:
        previous_output = task_outputs[task_index - 1]
    elif task_index > 0:  # Ensure task_index is positive
        previous_output = task_outputs[0]

2. Input Validation

Add validation on task_index to ensure it’s non-negative:

if task_index < 0:
    raise ValueError(f"Invalid task_index: {task_index}")

3. Documentation Enhancement

Include docstrings to clarify method functionality and argument expectations:

def _handle_conditional_task(self, ...):
    """
    Handles conditional task execution based on previous task outputs.
    
    Args:
        task_index (int): Current task index in the sequence
        task_outputs (list): List of previous task outputs
        
    Returns:
        Previous task output if conditions are met, None otherwise
    """

4. Additional Suggestions

• Unit Testing: Introduce specific tests for edge cases.
• Logging: Incorporate logging to track unexpected behavior.
• Type Hints: Leverage type hints for better clarity and maintenance.

from typing import List, Optional

def _handle_conditional_task(
    self,
    task_index: int,
    task_outputs: List[str],
    ...
) -> Optional[str]:

Conclusion

The changes presented in this PR are appropriate to address the immediate issue but could benefit from the suggested improvements for robustness and maintainability. Merging is suitable, with the understanding that future iterations should consider these enhancements for further refinement of the code's logic and safety.