Third `test_cancellation.py` group of the `run_in_actor` removal
(#477),
- `spawn_and_error` fans out each level's erroring one-shots as
concurrent `to_actor.run(fn, an=an)` tasks in a local `trio`
task-nursery (recursing per spawner subactor), as does the
test-body's top-level spawner loop.
- the deterministic exact-breadth nested-BEG shape dies with the
legacy teardown-reap: each level now groups whatever subset of
sub-tree errors relay before the first one's cancel wins, and
a single-member group gets unwrapped by the runtime's own
`collapse_eg()` at every actor boundary — so a fully-raced
tree relays a bare `RemoteActorError` chain.
- loosen the shape walk accordingly: accept a lone
`RemoteActorError` or a 1..breadth group whose members box
`ExceptionGroup` (multi-relay), `AssertionError` (collapsed
leaf chain), `RemoteActorError` (re-boxed collapsed chain) or
`BaseExceptionGroup` (runtime reap-deadline `Cancelled`
upgrade); fold the windows-only tolerances into the same walk.
- raced sibling `trio.Cancelled`s are now ABSORBED by the
task-nursery instead of landing in the group, so the MTF
shape-mismatch xfail should consistently xpass — note added to
drop the marker once CI confirms.
- add an `else: pytest.fail()` so a silently-clean tree can no
longer pass.
Gate: both depths green on `trio` (10 consecutive runs) +
`mp_spawn`.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi
fa8799d5bb