Adam Moussa 18e8382ef5 Make Cancelled PO status sticky via atomic write ... The PO merge path read status with a get_item (_is_cancelled) and then wrote with an unconditional update_item. Two defects followed from this: - Race (Issue A): a cancellation landing between the read and the write was silently un-cancelled by a revision carrying a non-cancelled po_status — a TOCTOU on a table with concurrent email processing. - Over-broad strip (Issue B): save_revision dropped po_status whenever the PO was Cancelled, so legitimate status updates on non-cancelled POs and status-less revisions were affected rather than only the true un-cancel transition. Enforce the invariant server-side instead. "Cancelled" is a sticky, authoritative status: once set, later new_po/revision emails may enrich other fields but must never move it to a non-cancelled status. When the payload carries a non-cancelled po_status, _merge_update issues the update_item guarded by ConditionExpression "attribute_not_exists(po_status) OR po_status <> :marker", evaluated atomically at write time, so a cancellation that lands first always wins. On ConditionalCheckFailedException the same fields are re-written without po_status/cancelled_at, enriching the record while Cancelled sticks. Payloads with no status change, or an already -Cancelled status, take a plain merge — the status is only ever suppressed on a real un-cancel. This removes the non-atomic get_item from the write path; _is_cancelled is deleted. Key schema and attribute names are unchanged, so the cross-stack purchase-orders contract (read-only by seahaven-slack-bot) holds. Add moto-backed tests covering un-cancel suppression with field enrichment, status-less merge onto a Cancelled PO, legitimate status updates on non-cancelled POs, new_po backfill of a Cancelled skeleton, fresh create/merge, and authoritative save_cancellation. Refs: #97		2026-07-15 19:57:07 -04:00
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conftest.py	Add pytest suite and enable tests in CI (#95)	2026-07-15 19:06:20 -04:00
requirements.txt	Make Cancelled PO status sticky via atomic write	2026-07-15 19:57:07 -04:00
test_pad_zip.py	Add pytest suite and enable tests in CI (#95)	2026-07-15 19:06:20 -04:00
test_parse_raw_email.py	Add pytest suite and enable tests in CI (#95)	2026-07-15 19:06:20 -04:00
test_po_merge.py	Make Cancelled PO status sticky via atomic write	2026-07-15 19:57:07 -04:00