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Avoid calling send() on awaiting native coroutine objects #963

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Avoid calling send() on awaiting native coroutine objects #963

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6 changes: 5 additions & 1 deletion rclpy/rclpy/task.py
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Original file line number Diff line number Diff line change
Expand Up @@ -212,6 +212,7 @@ def __init__(self, handler, args=None, kwargs=None, executor=None):
self._handler = handler(*args, **kwargs)
self._args = None
self._kwargs = None
self._future = None
# True while the task is being executed
self._executing = False
# Lock acquired to prevent task from executing in parallel with itself
Expand All @@ -236,7 +237,10 @@ def __call__(self):
if inspect.iscoroutine(self._handler):
# Execute a coroutine
try:
self._handler.send(None)
if self._future is None or self._future.done():
if self._future and self._future.exception():
raise self._future.exception()
self._future = self._handler.send(None)
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@sloretz sloretz Jul 9, 2022

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I don't think this can assume a coroutine will return a future. It seems like the behavior is specific to the async library being used (see #962 (comment)). This change is interesting though because it seems like it would both satisfy an rclpy.Future by calling send(None) until it raised StopIteration, and would only call asyncio.Future.__await__ once.

It still needs a way to wake the executor when an asyncio future completes, and given that asyncio isn't thread safe I bet there would be problems if a multithreaded executor was used.

except StopIteration as e:
# The coroutine finished; store the result
self._handler.close()
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