Wrapper around `trio.Nursery.start()` that DOESN'T mask
out-of-band cancellation as a lossy startup failure.
Picks the right re-raise: ambient `Cancelled` when
present, the genuine startup-protocol `RuntimeError`
otherwise.
The problem,
- `trio.Nursery.start()` raises a generic
`RuntimeError("child exited without calling
task_status.started()")` whenever the started task
exits BEFORE calling `task_status.started()` —
INCLUDING the common case where the child was
cancelled out-of-band by an *ancestor* cancel-scope
erroring/cancelling.
- In that case the original `trio.Cancelled` is
swallowed and the caller is left w/ an opaque,
root-cause-detached `RuntimeError`.
The fix,
- Catch the "...started" RTE.
- `await trio.lowlevel.checkpoint_if_cancelled()` —
re-raises the in-flight `Cancelled` IFF we're under
effective cancellation (ancestor-inclusive), carrying
trio's auto-generated reason which points at the true
root exc.
- If we're NOT cancelled the `checkpoint_if_cancelled()`
is a cheap no-op and we fall through to re-raise the
genuine startup-protocol RTE.
Re-export from `tractor.trionics` so callers don't have
to reach into `_taskc`.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
(cherry picked from commit 30e15925ba)
(cherry picked from commit 2b4589b1ee)
Gud Boi
90466ec016