Environment

• JRuby versions: 9.1.13.0 and 9.1.14.0
• Operating system and platform: Darwin Macintosh.lan 16.7.0 Darwin Kernel Version 16.7.0: Wed Oct 4 00:17:00 PDT 2017; root:xnu-3789.71.6~1/RELEASE_X86_64 x86_64

I'm getting the following error when using the "close_on_exec" APIs in TCP Server/Sockets:

require 'socket'
s = TCPServer.new("localhost", 9999)
s.close_on_exec = true
s.close_on_exec = true
# NotImplementedError: close_on_exec=
# 	from org/jruby/RubyIO.java:2172:in `close_on_exec='

At first I just thought this was one of the MRI/JRuby differences, but then I saw there are tests implemented for this in jruby, and the "did you mean" functionality throws out some weird errors when I'm pretty close to the method name:

s.close_on_exec
irb(main):006:0> s.close_on_exec
# NoMethodError: undefined method `close_on_exec' for #<TCPServer:fd 20>
# Did you mean?  close_on_exec?
#              close_on_exec=
#	from (irb):6:in `<eval>'
s.close_on_exec? # this should actually be defined, this is also a bug
# NotImplementedError: close_on_exec=
#	from org/jruby/RubyIO.java:2178:in `close_on_exec?'
#	from (irb):7:in `<eval>'

From what I understood, this should be implemented, and it's important for the "exec and keep IOs open in child process" functionality, which jruby should support.