# 任务异常从未被获取
future: <Task finished name='Task-5' coro=<fetch() done, defined at app.py:42> exception=ValueError('bad payload')>

- **ID:** `python/asyncio-task-exception-was-never-retrieved`
- **领域:** python
- **类别:** runtime_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

使用 asyncio.create_task() 创建的任务抛出异常，但无人 await 该任务或调用 task.exception()，导致异常在垃圾回收时以警告形式记录。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 3.8 | active | — | — |
| 3.9 | active | — | — |
| 3.10 | active | — | — |
| 3.11 | active | — | — |
| 3.12 | active | — | — |

## 解决方案

1. **** (90% 成功率)
   ```
   tasks = [asyncio.create_task(fetch(u)) for u in urls]
results = await asyncio.gather(*tasks, return_exceptions=True)
for r in results:
    if isinstance(r, Exception):
        logging.exception('task failed', exc_info=r)
   ```
2. **** (87% 成功率)
   ```
   def _on_done(t: asyncio.Task):
    if not t.cancelled() and t.exception():
        logging.error('task error', exc_info=t.exception())

t = asyncio.create_task(fetch(u))
t.add_done_callback(_on_done)
   ```

## 无效尝试

- **** — Hides the symptom but the task still fails silently and the error is lost. (85% 失败率)
- **** — Swallows real errors and produces no diagnostic; debugging becomes impossible. (80% 失败率)