Why does the streaming context manager not call stream.end() when exiting

[artificial-aidan]

In the example provided in the docs using the open() method on a stream creates a context manager that can be used to send and receive messages. One of the purposes of a context manager is to automate cleanup.

async with stub.BiDiMethod.open() as stream:
    await stream.send_request()  # needed to initiate a call
    while True:
        task = await task_queue.get()
        if task is None:
            await stream.end()
            break
        else:
            await stream.send_message(task)
            result = await stream.recv_message()
            await result_queue.add(task)

Why is the call to stream.end() necessary? Could that not be part of the stream.__aexit__() method?

[AlecZorab]

It's not obvious to me why the context manager doesn't call stream.cancel() (ie an explicit hangup, rather than just signalling that we're not going to send more data). Once we exit the context, the stream shouldn't be usable any more anyway, right?

[AlecZorab]

a flag on open to indicate that the context manager should cancel on exit could be really useful here