Is the documentation for Concurrent::Map#put_if_absent inverted?

[nerdrew]

The documentation looks like it says that it will return the new value if the key was not present and return nil if the new value was not inserted because the key was present.

It looks like the implementation is the opposite.

% pry -rconcurrent
[1] pry(main)> m = Concurrent::Map.new
=> #<Concurrent::Map:0x007f80e98124c0 entries=0 default_proc=nil>
[2] pry(main)> m.put_if_absent("a", 1)
=> nil
[3] pry(main)> m.put_if_absent("a", 2)
=> 1
[4] pry(main)> 

[nerdrew]

Documentation: http://ruby-concurrency.github.io/concurrent-ruby/1.1.x/Concurrent/Map.html#put_if_absent-instance_method

[pitr-ch]

Thanks @nerdrew! You are right. Could you contribute a fix please?

[edzhelyov]

Hey, is this still open? I can take a stab at fixing it. The code needs to change in accordance with the documentation, right?

[pitr-ch]

@edzhelyov thank you! Please do. The behaviour is correct, it has to match https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentHashMap.html#putIfAbsent-K-V- so the documentation needs a fix.