Redirect to IO.pipe on Windows causes inability to start a process

[barancev]

JRuby 9.2.8.0, Windows 10, Oracle Java 1.8.0_211

Reproduction sample:

r, w = IO.pipe
proc = ChildProcess.build('notepad.exe')
#proc.io.inherit!
proc.io.stdout = proc.io.stderr = w
proc.leader = true
proc.start
proc.wait
w.close

does not start Notepad and fails with this log:

C:\tools\jruby-9.2.8.0\bin\jruby.exe C:/devel/try-something/rb/sample.rb
ChildProcess::Error: Unknown error (Windows says "The operation completed successfully.", but it did not.)
             handle_for at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/lib.rb:326
     windows_handle_for at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/jruby.rb:48
             handle_for at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/lib.rb:307
  std_stream_handle_for at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/process_builder.rb:141
               setup_io at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/process_builder.rb:113
                  start at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/process_builder.rb:32
         launch_process at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/windows/process.rb:70
                  start at C:/tools/jruby-9.2.8.0/lib/ruby/gems/shared/gems/childprocess-3.0.0/lib/childprocess/abstract_process.rb:81
                 <main> at C:/devel/try-something/rb/sample.rb:12

If I uncomment proc.io.inherit! instead of redirecting to pipes everything works like a charm.

[sds]

Hey @barancev, thanks for the report.

What you are trying to do is pretty straightforward, but this particular combination of tools (JRuby + Windows) is a little off the beaten path. Perhaps there are limitations with JRuby's implementation of IO.pipe that you're hitting in this context which don't play well with the process builder.

Would appreciate help from interested folks in investigating this particular issue. Thanks!

[barancev]

Is it better to report this to the JRuby team?

[sds]

I would potentially open a bug with the JRuby team if you are unable to reproduce this bug on Windows with vanilla MRI Ruby.

The issue here is that we have code to use Windows-specific logic when running in JRuby on Windows, and I'm not sure how often this logic is exercised. The JRuby team may come back to say that it's an issue with the implementation.

If, however, you are able to get this to work with vanilla Ruby and not JRuby, that may suggest an issue with JRuby itself. Appreciate your help in investigating.

[sds]

Closing as there does not appear to be an effort to address. Happy to merge a pull request fixing the issue, if it is indeed specific to childprocess. Thanks!

[barancev]

Sorry for silence, I've implemented a workaround and forgot about this issue...
Yes, it works with vanilla Ruby, so I'll report this issue to JRuby.

[barancev]

Here it is: jruby/jruby#6102