Remove pointless try/except in polling_task

[alexrudd2]

See #2090. This PR goes a step further.

This code is a stack of clever hacks.

pymodbus/pymodbus/transport/serialtransport.py

Lines 45 to 48 in d6704a2

	if self.poll_task:
	self.poll_task.cancel()
	self.future = asyncio.ensure_future(self.poll_task)
	self.poll_task = None

The purpose of this code is to cancel self.poll_task() and then set it to None afterwards.

Because the code is sync, await cannot be used to ensure the cancellation.
Hack #1 - use ensure_future

Then ruff complains with RUF006. This could have been safely ignored - nobody cares if the GC cleans up, since it's immediately set to None. Instead...
Hack #2 - use self.future to hold a reference.

Next mypy complains that self.future is untyped.
Hack #3 - add an annotation to the constructor.

Looking at polling_task, I see no purpose to catching asyncio.CancelledTask. All it does is call self.close().... which is the very code that cancelled it!
I think the whole try/Except and stack of hacks can be removed. :)

[alexrudd2]

If the try/except is still wanted, the solution is to just ignore ruff and delete self.future

asyncio.ensure_future(self.poll_task)  # noqa: RUF006

[janiversen]

Your idea is not bad, but it seems you broke something so that the reconnect does not run.

The cancelled most likely comes from the same code, as you write, but it might also come from transport (I think),

[janiversen]

If we can avoid the try/cancel I am all in favour, I just cannot see how the pyserial object is being closed if the task is cancelled.

[janiversen]

hmmm the failing test in 3.10 is a tcp test, I am confused

[alexrudd2]

Is there any way that poll_task gets cancelled except explicitly in self.close()?

[janiversen]

I am not sure if asyncio.protocol cancels running tasks in some cases, apart from that I think you are correct that it is only self.close() that does it.

[alexrudd2]

hmmm the failing test in 3.10 is a tcp test, I am confused

I've noticed we have a rare flaky test again, but have not investigated further.

[janiversen]

I will keep an eye open, I have had seen it lately.