gh-149740: Remove redundant self.empty() check in asyncio.Queue.get()

[deadlovelll]

Bug description:

In Lib/asyncio/queues.py, Queue.get() contains a redundant call to self.empty() inside its waiting loop:

async def get(self):
    while self.empty():
        if self._is_shutdown and self.empty():   # second self.empty() is redundant
            raise QueueShutDown

self.empty() is guaranteed to be true by the enclosing while self.empty() the loop body cannot execute otherwise. This check is a dead code.

Proposed fix:

Drop the redundant and self.empty():

while self.empty():
    if self._is_shutdown:
        raise QueueShutDown

This PR is cleanup only, no behavior change

• Issue: Redundant self.empty() check in asyncio.Queue.get() #149740

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[picnixz]

I don't think it's correct. See the issue.

[picnixz]

Looking at the other parts of the code, I think it would make indeed more sense to consistently raise on shutdown whether the queue is empty or not. So it is not dead code but it rathet looks like a bug to me.

[MojoVampire]

You could just change the loop to while self.empty() and not self._is_shutdown:; get_nowait already rechecks all this stuff when it's called, and would raise the necessary exception for us.

[picnixz]

I would prefer keeping this as is, so to keep the symmetry in the get() method.