[ruby-core:58556] [ruby-trunk - Feature #9145] Queue#pop(true) return nil if empty instead of raising ThreadError

["jsc (Justin Collins)" <redmine@ruby-lang.org>]

Issue #9145 has been updated by jsc (Justin Collins).


Glass_saga (Masaki Matsushita) wrote:
> I think we can't change default behavior of Queue#pop(true) because some code expects ThreadError to be raised.
> However, it may be possible to introduce new keyword argument like following:
> 
> q = Queue.new
> while next_item = q.pop(true, exception: false) # it doesn't raise ThreadError and returns nil.
>   # do something
> end

That would work for me.
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Feature #9145: Queue#pop(true) return nil if empty instead of raising ThreadError
https://bugs.ruby-lang.org/issues/9145#change-43134

Author: jsc (Justin Collins)
Status: Feedback
Priority: Normal
Assignee: 
Category: ext
Target version: 


I propose the non-blocking form of Queue#pop behave like Array#pop and return nil when empty.

Current behavior is to raise a ThreadError, with a message indicating the queue is empty.

For example:

q = Queue.new
begin
  loop do
    next_item = q.pop(true)
  end
rescue ThreadError
  # queue is empty...or maybe something bad happened
end

Instead, this could be

q = Queue.new
while next_item = q.pop(true)
end

Alternatively, raise an exception that is a subclass of ThreadError with a more specific name, such as "QueueEmpty". This would be a small improvement while remaining compatible with existing code.


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