This fixes an previously undetected bug where if an
`.open_channel_from()` spawned task errored the error would not be
propagated to the `trio` side and instead would fail silently with
a console log error. What was most odd is that it only seems easy to
trigger when you put a slight task sleep before the error is raised
(:eyeroll:). This patch adds a few things to address this and just in
general improve iter-task lifetime syncing:
- add `LinkedTaskChannel._trio_exited: bool` a flag set from the `trio`
side when the channel block exits.
- add a `wait_on_aio_task: bool` flag to `translate_aio_errors` which
toggles whether to wait the `asyncio` task termination event on exit.
- cancel the `asyncio` task if the trio side has ended, when
`._trio_exited == True`.
- always close the `trio` mem channel when the task exits such that
the `asyncio` side can error on any next `.send()` call.
When an `asyncio` side task errors or is cancelled we now explicitly
report the traceback and task name if possible as well as the source
reason for the error (some come from the `trio` side).
Further, properly set any `trio` side exception (after unwrapping it
from the `outcome.Error`) on the future that runs the `trio` guest run.
Better encapsulate all the mem-chan, Queue, sync-primitives inside our
linked task channel in order to avoid `mypy`'s complaints about monkey
patching. This also sets footing for adding an `asyncio`-side channel
API that can be used more like this `trio`-side API.
For whatever reason `trio` seems to be swallowing this exception when
raised in the `trio` task so instead wrap it in our own non-base
exception type: `AsyncioCancelled` and raise that when the `asyncio`
task cancels itself internally using `raise <err> from <src_err>` style.
Further don't bother cancelling the `trio` task (via cancel scope)
since we we can just use the recv mem chan closure error as a signal
and explicitly lookup any set asyncio error.
Wraps the pairs of underlying `trio` mem chans and the `asyncio.Queue`
with this new composite which will be delivered from `open_channel_from()`.
This allows for both sending and receiving values from the `asyncio`
task (2 way msg passing) as well controls for cancelling or waiting on
the task.
Factor `asyncio` translation and re-raising logic into a new closure
which is run on both `trio` side error handling as well as on normal
termination to avoid missing `asyncio` errors even when `trio` task
cancellation is handled first.
Only close the `trio` mem chans on `trio` task termination *iff*
the task was spawned using `open_channel_from()`:
- on `open_channel_from()` exit, mem chan closure is the desired semantic
- on `run_task()` we normally only return a single value or error and
if the channel is closed before the error is raised we may propagate
a `trio.EndOfChannel` instead of the desired underlying `asyncio`
task's error
Pull the common `asyncio` -> `trio` error translation logic into
a common context manager and don't expect a final result to be captured
when using `open_channel_from()` since it's a manager interface and it
would be clunky to try and deliver some "final result" after exit.
Close the mem chan before cancelling the `trio` task in order to ensure
we retrieve whatever error is shuttled from `asyncio` before the channel
read is potentially cancelled (previously a race?).
Handle `asyncio.CancelledError` specially such that we raise it directly
(instead of `raise aio_cancelled from other_err`) since it *is* the
source error in the case where the cancellation is `asyncio` internal.
Clearly this wasn't developed against a task that spawned just an async
func in `asyncio`.. Fix all that and remove a bunch of unnecessary func
layers. Add provisional support for the target receiving the `to_trio`
and `from_trio` channels and for the @tractor.stream marker.
This should mostly maintain top level SC principles for any task spawned
using `tractor.to_asyncio.run()`. When the `asyncio` task completes make
sure to cancel the pertaining `trio` cancel scope and raise any error
that may have resulted. This interface uses `trio`'s "guest-mode" to run
`asyncio` loop using a special entrypoint which is handed to Python
during process spawn.
Tyler Goodlet