isaiahiruoha opened a new pull request, #54249: URL: https://github.com/apache/airflow/pull/54249
closes: #52881 ### Problem Description When tasks within nested task groups try to access XCom values from sibling tasks in the same mapped parent task group instance, the system incorrectly uses `map_index=null` instead of the correct map index, causing XCom lookup failures. ##### Example DAG Structure <img width="1033" height="494" alt="Screenshot 2025-08-07 at 1 47 06 PM" src="https://github.com/user-attachments/assets/f6c1767b-a999-470d-b090-478643dcdc01"; /> ##### Error Observed (Note: map_index=null) ```javascript No XCom value found; defaulting to None.: key="return_value": dag_id="test_dag": task_id="expandable_task_group.inner_task_group.alter_input": run_id="manual__2025-07-04T14:56:47.815002+00:00": map_index=null ``` ##### Related Code The issue is in `airflow-core/src/airflow/api_fastapi/execution_api/routes/task_instances.py` in the `_get_upstream_map_indexes` function. The logic only checks the immediate parent task group (upstream_task.task_group) but doesn't consider nested scenarios where tasks are within a regular task group that is itself within a mapped task group. ##### Proposed Solution Replace the immediate parent check with a hierarchy-aware check using `get_closest_mapped_task_group()`. This ensures that both tasks recognize they share the same mapped task group ancestor and use the same map_index. ### Testing - Verified proposed solution resolves issue: #52881 when tested locally using `breeze start-airflow` against the latest main branch development environment. - Added `test_nested_mapped_task_group_upstream_indexes` to verify that tasks in nested mapped task groups correctly resolve upstream map indexes. <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <!-- Thank you for contributing! Please make sure that your code changes are covered with tests. And in case of new features or big changes remember to adjust the documentation. Feel free to ping committers for the review! In case of an existing issue, reference it using one of the following: closes: #ISSUE related: #ISSUE How to write a good git commit message: http://chris.beams.io/posts/git-commit/ --> <!-- Please keep an empty line above the dashes. --> --- **^ Add meaningful description above** Read the **[Pull Request Guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#pull-request-guidelines)** for more information. In case of fundamental code changes, an Airflow Improvement Proposal ([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvement+Proposals)) is needed. In case of a new dependency, check compliance with the [ASF 3rd Party License Policy](https://www.apache.org/legal/resolved.html#category-x). In case of backwards incompatible changes please leave a note in a newsfragment file, named `{pr_number}.significant.rst` or `{issue_number}.significant.rst`, in [airflow-core/newsfragments](https://github.com/apache/airflow/tree/main/airflow-core/newsfragments). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
