Dev-iL opened a new pull request, #65586:
URL: https://github.com/apache/airflow/pull/65586
related: #64430
## Summary
- Add `dag[task_id]` subscript syntax to `DAG` and `SerializedDAG`,
mirroring the existing `TaskGroup.__getitem__` pattern.
- Update `TaskGroup.__getitem__` to raise `TaskItemNotFound` (instead of a
raw `KeyError`) on a miss, so callers can catch either `KeyError` or
`TaskNotFound`.
- Introduce `TaskItemNotFound(TaskNotFound, KeyError)` as a new exception in
`airflow.sdk.exceptions` (and re-export it from `airflow.exceptions`) — a
`KeyError` subtype that also satisfies `TaskNotFound`, giving callers
flexibility without breaking existing `KeyError` handlers.
## Details
| Component | Change |
|-----------|--------|
| `task-sdk/src/airflow/sdk/exceptions.py` | Add
`TaskItemNotFound(TaskNotFound, KeyError)` |
| `airflow-core/src/airflow/exceptions.py` | Re-export `TaskItemNotFound`;
add fallback stub |
| `task-sdk/src/airflow/sdk/definitions/dag.py` | Add `DAG.__getitem__`
(delegates to `get_task`, re-raises as `TaskItemNotFound`) |
| `task-sdk/src/airflow/sdk/definitions/taskgroup.py` | Update
`TaskGroup.__getitem__` to re-raise `KeyError` as `TaskItemNotFound` |
| `airflow-core/src/airflow/serialization/definitions/dag.py` | Add
`SerializedDAG.__getitem__` for consistency |
## Usage
```python
with DAG("my_dag", ...) as dag:
t = BashOperator(task_id="my_task", bash_command="echo 1")
# New: subscript access
assert dag["my_task"] is t
# Raises TaskItemNotFound (catchable as KeyError or TaskNotFound)
dag["nonexistent"] # raises TaskItemNotFound
# TaskGroup subscript now raises TaskItemNotFound instead of raw KeyError
with TaskGroup("section") as tg:
...
tg["nonexistent"] # raises TaskItemNotFound
```
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* For fundamental code changes, an Airflow Improvement Proposal
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