shahar1 opened a new pull request, #67684:
URL: https://github.com/apache/airflow/pull/67684
A task using a "fast triggered" trigger rule (`ONE_FAILED`, `ONE_SUCCESS`,
`ONE_DONE`) inside a **mapped task group** was evaluated against *every*
expanded instance of its upstream, instead of the upstream instance that shares
its own map index. As a result, a single failed (or succeeded) upstream
instance wrongly triggered the rule for **every** expanded instance of the task.
For example, in the reproduction from the issue, `divide(0)` fails while
`divide(1..3)` succeed, yet the mapped `report_failure` task (`ONE_FAILED`) ran
for *all* map indexes instead of only index `0`.
### Root cause
`TriggerRuleDep._get_relevant_upstream_map_indexes` short-circuits to
"depend on every upstream instance" for the fast-triggered rules when the
upstream is not an expansion dependency of the group (introduced in #44937 to
fix #34023). That broad behavior is only needed for the **not-yet-expanded
summary task instance** (`map_index < 0`), so the task is not prematurely
skipped before the mapped task group expands. Applying it to the
already-expanded instances broke per-index correspondence.
### Fix
Restrict the special case to the summary instance (`ti.map_index < 0`).
Expanded instances now use the normal per-map-index upstream resolution, so
each `report_failure[k]` depends on `divide[k]` only.
### Tests
- Added `test_one_failed_trigger_rule_in_mapped_task_group_is_per_index`
(the issue's repro: `report_failure` is now `{0: success, 1..3: skipped}`).
- Added
`test_one_failed_trigger_rule_runs_on_indirect_failure_in_mapped_task_group`
(end-to-end guard for the #34023 behavior).
- The existing
`test_mapped_tasks_in_mapped_task_group_waits_for_upstreams_to_complete`
(#44937, premature-skip guard) still passes.
closes: #50210
---
##### Was generative AI tooling used to co-author this PR?
- [X] Yes — Claude Code (Opus 4.8)
Generated-by: Claude Code (Opus 4.8) following [the
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