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Update the stale cycle-detection comment on topological_sort - #74079
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pierrejeambrun merged 1 commit intoOct 2, 2026
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…ogical_sort DAG.check_cycle was the only guard this comment named, but a Lang-SDK Dag never runs it: it has no Python DAG object to call it on. The Dag processor now rejects a cyclic Lang-SDK Dag of its own accord, through DagSerialization.validate_serialized_dag, so the comment should name both guards rather than the one that does not cover every author.
pierrejeambrun
merged commit Oct 2, 2026
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October 2, 2026 09:59
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Stack: #74034, #74040, #74041, #74042, #74035, this PR
Why
SerializedTaskGroup.topological_sort's docstring saysDAG.check_cycleis what keeps a cyclic Dag from ever reaching it. That was true, but only for a Python-authored Dag — a Lang-SDK Dag has no PythonDAGobject to callcheck_cycleon, so the comment overstated the actual guarantee for the other authoring path.#74035 closes that gap: the Dag processor now runs
DagSerialization.validate_serialized_dagon every Dag a Lang-SDK runtime returns, rejecting one with a cycle as an import error before it is ever stored (both this andDAG.check_cycleare backed by the shareddetect_cyclefrom #74034). The comment should name both guards.What
One docstring update, no behavior change.
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