Closes the #99758 review P1 (andrexibiza): with a generation claim in
play, `interrupt()` called `_admit_hard_cancel()` BEFORE the claim was
validated at the final mutation edge, and the production
`CompressionCommitFence.cancel_before_commit()` irreversibly sets
`_cancelled = True` whenever no commit has started. So a watchdog abort
that ultimately DECLINED (real progress landed in the window, claim went
stale) had already killed the recovered turn's legitimate pending
compression commit — `begin_commit()` refuses a cancelled fence forever.
Generation authority covered interrupt publication but not the
compression-fence mutation that preceded it.
Split hard-cancel admission into two halves:
- `_wait_for_compression_commit()` runs pre-claim and is NON-mutating:
it only blocks when `commit_in_flight` is true (the started-commit
branch of the production fence waits for `finish_commit` without
cancelling), so the interrupt still publishes only after an in-flight
SessionDB mutation has finished — exactly as before.
- `_cancel_pending_compression_commit()` runs AFTER
`_consume_claim_and_publish_first_state()` survives, so the
destructive pending-commit cancellation can never outlive a stale
claim. If a commit crossed its boundary in between, it is no longer
fence-cancellable and completes on its own.
Regression coverage (both use the real `CompressionCommitFence`):
- `test_declined_abort_does_not_cancel_pending_compression_commit`:
parks the interrupt at the claim-reservation release, lands real
progress (G+1), lets the interrupt decline, then proves
`fence.begin_commit()` still admits. Red on the pre-fix tree
(mutation-checked: the fence was left cancelled).
- `test_declined_abort_parks_and_leaves_fence_operational`: the
in-flight-commit window variant — activity lands while the interrupt
waits on a started commit; the interrupt declines and a fresh
`begin_commit()` still admits afterwards.
- The round-6 witness (`...resumes_inside_interrupt_publication`) now
models an in-flight commit (`commit_in_flight = True`) so its park
point stays inside the pre-claim wait, matching the new admission
shape.
Also updates the `interrupt()` docstring for the deferred destructive
cancellation.
kshitijk4poor
f20bbfa40d