[ruby-core:72178] [Ruby trunk - Bug #11822] Semantics of Queue#pop after close are wrong

[funny.falcon@gmail.com]

Issue #11822 has been updated by Yura Sokolov.


Charles, closing queue only prevents adding new elements to. It should not delete already added items.

Look at Golang's channels, they behaves same way. It is really most useful behaviour.

Deleting already added items would be very unfriendly behaviour. 

Perhaps, you complain about documentation? It should be clearer about actual way.

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Bug #11822: Semantics of Queue#pop after close are wrong
https://bugs.ruby-lang.org/issues/11822#change-55592

* Author: Charles Nutter
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
Current test/ruby/thread/test_queue.rb test_close has the following assertion that seems wrong to me:

```ruby
  def test_close
    [->{Queue.new}, ->{SizedQueue.new 3}].each do |qcreate|
      q = qcreate.call
      assert_equal false, q.closed?
      q << :something
      assert_equal q, q.close
      assert q.closed?
      assert_raise_with_message(ClosedQueueError, /closed/){q << :nothing}
      assert_equal q.pop, :something  # <<< THIS ONE
      assert_nil q.pop
      assert_nil q.pop
      # non-blocking
      assert_raise_with_message(ThreadError, /queue empty/){q.pop(non_block=true)}
    end
  end
```

Once a queue is closed, I don't think it should ever return a result anymore. The queue should be cleared and pop should always return nil.

In r52691, ko1 states that "deq'ing on closed queue returns nil, always." This test does not match that behavior.



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