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Update the stale cycle-detection comment on topological_sort #74079

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Merged
pierrejeambrun merged 1 commit into from
Oct 2, 2026
Merged

Update the stale cycle-detection comment on topological_sort #74079

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9 changes: 6 additions & 3 deletions airflow-core/src/airflow/serialization/definitions/taskgroup.py
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Original file line number Diff line number Diff line change
Expand Up @@ -237,9 +237,12 @@ def topological_sort(
Sort children topologically — a task always comes after its upstream dependencies.

See ``TaskGroup.topological_sort`` in task-sdk for the algorithm. Cycles are
treated as corrupt input: ``DAG.check_cycle`` rejects cyclic Dags before
serialization, so a cycle reaching this code indicates malformed serialized data,
and we raise ``ValueError`` rather than silently looping forever.
treated as corrupt input: a Python Dag's cycle is rejected by ``DAG.check_cycle``
before serialization, and a Lang-SDK Dag's cycle is rejected by
``DagSerialization.validate_serialized_dag`` when the Dag processor receives it
(both call the shared ``detect_cycle``). A cycle reaching this code indicates
malformed serialized data, and we raise ``ValueError`` rather than silently
looping forever.
"""
children = self.children
if not children:
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