Open3.popen3(...) is broken in 1.9 mode

I note here that Open3::popen3 has a short circuit that returns IO::open3 for JRuby (https://github.com/jruby/jruby/blob/3b60780b07e8dc5e480987357098756bd281ddf0/lib/ruby/1.9/open3.rb#L74).

It was not immediately obvious to me how we might reconcile this with IO::open3 alone. We can get the child Java Process easily, but it seemed nontrivial to build a RubyThread from it.

Oh okay, do you think it is a solvable problem?
I'd like to add JRuby compatibility to a gem, and
this is a blocker at the moment.

So, there is a way to build a RubyThread from a Java Process (RubyProcess.detach()).

A naive approach goes something like this:

POpenTuple tuple = popenSpecial(context, args);
long pid = ShellLauncher.getPidFromProcess(tuple.process);
IRubyObject thr = RubyProcess.detach(context, runtime.getProcess(), runtime.newFixnum(pid));

but this fails rather miserably.

$ jruby -S irb
irb(main):001:0> require 'open3'; i,o,e,t = Open3.popen3("ls")
=> [#<IO:fd 140>, #<IO:fd 139>, #<IO:fd 141>, #<Thread:0x2eb86778 run>]
irb(main):002:0> t
=> #<Thread:0x2eb86778 dead>
irb(main):003:0> t.value
Errno::ECHILD: No child processes - No child processes

I'm probably missing something obvious. I welcome suggestions and improvements.

Fix in 1.7.1 along with other process-launching APIs.

I tried this same thing in jruby-1.7.2 and in jruby-head (1.7.3 pre), but the problem still seems to exist.

[ asymptotic ] > irb
jruby-1.7.3.dev:001 > require 'open3'
=> true
jruby-1.7.3.dev:002 > Open3::popen3('ls')
=> #<IO:fd 9>, #<IO:fd 8>, #<IO:fd 10>

Note that only three objects are returned, not the expected four. The thread object is missing. If this was fixed in 1.7.1, it seems maybe the problem recurred in 1.7.2.