fix(tasks): an aborted wait must not leave a settled task notice-suppressed (review finding)

Two windows where settle() could read a live waiter count, mark the
task reported (suppressing the completion notice), and then watch that
waiter reject with 'wait aborted' delivering nothing — leaving the
owning session with no terminal notification at all:

- abort and settlement in the same tick, settle continuation ordered
  first: the waiter now un-counts itself SYNCHRONOUSLY inside onAbort
  (the finally decrement alone lands a microtask too late), so the
  settle path sees no live waiter and the notice fires;
- abort landing after settlement but before the wait's resolve
  microtask: the wait now resolves and DELIVERS the terminal snapshot
  it owes instead of rejecting (settlement suppressed the notice on
  this waiter's behalf).

Both windows pinned by deterministic tests that fail on the previous
implementation; wait()'s abort contract updated in JSDoc/README/RFC.
This commit is contained in:
Yichen Jiang
2026-07-09 23:08:26 +08:00
parent 032510a85a
commit 43d60286e3
4 changed files with 74 additions and 7 deletions

View File

@@ -8,7 +8,7 @@ The background task registry (`ctx.tasks`): a runtime-global, CONCRETE service (
- `get(id, caller?)` / `list(caller?)` — non-consuming snapshots; `list` returns only caller-owned plus unowned tasks (a global listing would leak foreign labels).
- `read(id, caller?): TaskRead` — stream kinds consume the per-task cursor (v1's single intended reader is the owning model — a non-consuming multi-reader surface would be a cursor/snapshot API extension, not a `read` change); final kinds read the terminal output idempotently.
- `kill(id, caller?, reason?)` — `'requested'` (live task: producer `cancel` runs first — a throw fails the kill loud and leaves the task untouched — then `stopping`) or `'already-terminal'`. Every successful kill marks the task `reported` (the killer saw the end → completion notice suppressed).
- `wait(id, timeoutMs, caller?, signal?)` — resolves with the terminal snapshot (marked `reported`), or the live snapshot at timeout; an aborted signal rejects the WAIT only. Timing is a [`dsh-timeout`](../../util/timeout/README.md) `deadline()` scoped to the `TASK_WAIT_TIMEOUT` code, so a nested foreign deadline never misreads as a wait timeout.
- `wait(id, timeoutMs, caller?, signal?)` — resolves with the terminal snapshot (marked `reported`), or the live snapshot at timeout; an aborted signal rejects the WAIT only — unless the task already settled, in which case the wait still resolves and delivers the terminal snapshot (settlement suppressed the completion notice on this waiter's behalf, so rejecting would leave the finish both unreported and un-noticed). Timing is a [`dsh-timeout`](../../util/timeout/README.md) `deadline()` scoped to the `TASK_WAIT_TIMEOUT` code, so a nested foreign deadline never misreads as a wait timeout.
- `onTaskDone(listener)` — exactly once per task with the terminal snapshot; effect-scoped, per-listener containment, silent after service disposal.
- `attachSurface(name)` — declares a control surface exists (the model tools, or a deployment's custom surface); effect-scoped.