Fix: dag next-execution --table crashes when no next run exists (#67394)

[bramhanandlingala]

When you run airflow dags next-execution <dag_id> --table, it crashes with an AttributeError if the DAG has no upcoming scheduled run.
For example when
schedule=None, or when a @once DAG has already run and you ask for a second execution with --num-executions 2.

The bug is in the --table branch of dag_next_execution. It used a one-liner list comprehension that called operator.attrgetter on every item yielded by iter_next_dagrun_info(). The problem is that iterator can yield None to signal "no more runs", and calling an attribute getter on None blows up immediately.

The non-table code path right below it already handles this correctly. it checks if info is None, prints a warning to stderr, and carries on. The table branch just never got the same treatment.

This PR fixes it by expanding the list comprehension into a proper loop, adding the same None check, and emitting the same warning message.
Valid runs are collected into a list and printed as a table as before; None entries are skipped with a warning.

Are you willing to submit PR?
Yes, if helpful.

Code of Conduct

I agree to follow this project's Code of Conduct

closes: #67394

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Important

🛠️ Maintainer triage note for @bramhanandlingala · by @potiuk · 2026-07-18 16:36 UTC

I've removed the ready for maintainer review label — the next step here is yours:

• ❌ Merge conflicts with main. See docs.

It'll return to the maintainer queue automatically once resolved — no need to re-add the label by hand. See the Pull Request quality criteria for details.

The ball is in your court — you've been assigned. Rebase onto main, push, then mark it Ready for review.

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

[boring-cyborg]

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[vamsivasireddy-ops]

Great way to handle!

[bramhanandlingala]

@ashb @XD-DENG @bolkedebruin @jedcunningham @ephraimbuddy
Could you please review this PR? It touches DAG-related code.

[potiuk]

@bramhanandlingala — I've removed the ready for maintainer review label because the next step here is yours: this branch now has merge conflicts with main. It'll go back into the maintainer queue automatically once you rebase onto the latest main and push — no need to re-add the label by hand. There's no rush.

_{Automated triage note drafted by an AI-assisted tool — may get things wrong; a real Apache Airflow maintainer takes the next look once it's green. (why automated)}

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Drafted-by: Claude Code (Opus 4.8); reviewed by @potiuk before posting

[potiuk]

@bramhanandlingala This PR has been converted to draft because it does not yet meet our Pull Request quality criteria.

Issues found:

• ❌ Merge conflicts: This PR has merge conflicts with main and cannot be merged as-is. Rebase locally and resolve them: git fetch upstream main && git rebase upstream/main, resolve the conflicts, then force-push.

Note: Your branch is 1281 commits behind main. Some check failures may be caused by changes in the base branch rather than by your PR. Please rebase your branch and push again to get up-to-date CI results.

What to do next:

• Fix each issue listed above.
• Make sure static checks pass locally (prek run --from-ref main --stage pre-commit).
• Mark the PR as "Ready for review" when you're done.

Converting a PR to draft is not a rejection — it is an invitation to bring the PR up to the project's standards so that maintainer review time is spent productively. There is no rush — take your time and work at your own pace. We appreciate your contribution and are happy to wait for updates. If you have questions, feel free to ask on the Airflow Slack.

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Note: This comment was drafted by an AI-assisted triage tool and may contain mistakes. Once you have addressed the points above, an Apache Airflow maintainer — a real person — will take the next look at your PR. We use this two-stage triage process so that our maintainers' limited time is spent where it matters most: the conversation with you.

[shahar1]

See #70437 (review)