Unable to spawn jruby-1.7.3 subprocess within ruby-1.9.3

[jkndrkn]

Has anyone been able to spawn ruby subprocesses running different versions of ruby than the parent process?

I'm running rbenv 0.4.0-20-ga7da069 on Mac OS X 10.6.8.

I'm trying to see if the below scenario is feasible. I took over a project where the following was working reliably for some time but after upgrading rbenv, ruby-build, and updating bundler and gem, it broke.

# foo.rb
Dir.chdir("./jruby_project") do
  cmd = "bundle exec bin/bar.rb"
  IO.popen(cmd, "r").tap {|io| p io.readline}
end

If I call the above foo.rb in a project running ruby-1.9.3 using bundle exec foo.rb, then the above script fails to run ./jruby_project/bin/bar.rb using the version of jruby specified in ./jruby_project/.rbenv-version. Instead, it runs it using ruby-1.9.3.

Inspecting the ENV vars inside of bar.rb shows that RBENV_VERSION, PATH, and a number of other vars show that bar.rb is running using ruby-1.9.3 instead of jruby.

I have tried other ways of spawning a subprocess such as the backtick operator and these result in the same issue.

[mislav]

Without any editing of the PATH environment variable, you can't spawn different Ruby version subprocesses from a ruby process initiated with rbenv. See #121

[jkndrkn]

Thanks for the quick replies on this issue!

I found a fix that doesn't require editing of the PATH environment variable.

Dir.chdir("./jruby_project") do
  cmd = "rbenv exec bundle exec bin/bar.rb".split(" ")
  IO.popen([{"RBENV_VERSION" => "jruby-1.7.3"}, *cmd], "r").tap {|io| p io.readline}
end

Process.spawn, IO.popen, Open3.popen3, etc. all allow setting env vars. Using rbenv exec allows the subprocess to honor RBENV_VERSION and spawn with a different version than the parent ruby process initiated with rbenv.

[mislav]

Oh, nice workaround for your problem. But I don't want to advise this to everyone, because people shouldn't be using rbenv exec that often (it's a semi-internal command). Also, this makes your script unusable by a teammate who's using a different Ruby version manager than rbenv.