Fix grid view topological sort for cross-group dependencies

[alex-stiff]

When specifying group dependencies like first_stage.end >> second_stage.start, the ordering within the Airflow UI does not respect the default topological sorting.

Minimal DAG to reproduce:

from datetime import datetime
from airflow.sdk import DAG, task, TaskGroup


@task
def noop_task():
    pass


with DAG("grid_sort_bug_repro", start_date=datetime(2024, 1, 1), schedule=None, catchup=False):

    with TaskGroup("stage_b"):
        b_start = noop_task()
        b_end = noop_task()
        b_start >> b_end

    with TaskGroup("stage_a"):
        a_start = noop_task()
        a_end = noop_task()
        a_start >> a_end

    b_end >> a_start  # task-level dep, bypasses group-level relationship

This shows in the grid view UI as:

stage_a
stage_b

Which is alphabetical, rather than the desired stage_b coming before stage_a.

This is happening because the _project_child_deps function only checks child.upstream_task_ids populated explicitly. We need to also scan the upstream_task_ids of the TaskGroup's root tasks so that the tasks within the group are also visible to this function.

---

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

---

• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

---

Important

🛠️ Maintainer triage note for @alex-stiff · by @potiuk · 2026-06-17 14:51 UTC

Helpful heads-up from the maintainers — please address before this PR can be reviewed:

• Static / docs checks failing (CI image checks / Static checks). Run them locally with prek run --all-files (or pre-commit run --all-files) and push the fixes.
• Failing test jobs: Low dep tests:core / All-core:LowestDeps:14:3.10:Always...Core, MySQL tests: core / DB-core:MySQL:8.0:3.10:Always...Core, Postgres tests: core / DB-core:Postgres:14:3.10:Always...Core, Sqlite tests: core / DB-core:Sqlite:3.10:Always...Core. Reproduce and fix locally, then push.
• See the Pull Request quality criteria.

The ball is in your court — you've been assigned to this PR. Fix the above, then mark it Ready for review.

_{Automated triage — may be imperfect; a maintainer takes the next look.}

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contributors' Guide
Here are some useful points:

• Pay attention to the quality of your code (ruff, mypy and type annotations). Our prek-hooks will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example Dag that shows how users should use it.
• Consider using Breeze environment for testing locally, it's a heavy docker but it ships with a working Airflow and a lot of integrations.
• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
• Please follow ASF Code of Conduct for all communication including (but not limited to) comments on Pull Requests, Mailing list and Slack.
• Be sure to read the Airflow Coding style.
• Always keep your Pull Requests rebased, otherwise your build might fail due to changes not related to your commits.
  Apache Airflow is a community-driven project and together we are making it better 🚀.
  In case of doubts contact the developers at:
  Mailing List: dev@airflow.apache.org
  Slack: https://s.apache.org/airflow-slack

[ashb]

Please add unit tests covering it.

[alex-stiff]

Please add unit tests covering it.

Thank you, added.

[potiuk]

Note

🛠️ Maintainer triage note for @alex-stiff · by @potiuk · 2026-07-08 16:05 UTC

This draft has been inactive for ~20 days, so I'm closing it to keep the review queue tidy — no judgment on the work itself.

No rush — reopen it (or open a fresh PR) whenever you're ready to continue; nothing is lost.

_{Automated triage — may be imperfect; a maintainer takes the next look.}

[alex-stiff]

@potiuk would you mind reopening this for me please, I don't seem to have perms! Thank you.