JRuby IRB readline issue on linux under a non-forked PTY

[byteit101]

Environment

• jruby 9.1.15.0 (2.3.3) 2017-12-07 929fde8 OpenJDK 64-Bit Server VM 25.151-b12 on 1.8.0_151-b12 +jit [linux-x86_64]
• On several linuxes (RHEL and Debian)
• rspec and ffi gems installed
• Might also work on OSX; haven't tried

Test

I wrote this RSpec test that passes 3/3 on MRI, yet only passes 1/3 on JRuby:

https://gist.github.com/byteit101/241c5bb712c0d28930163ff0d88dc878

Note I had to patch PTY.open to avoid #5004

I think that the cases are fairly self explanatory, but in short it seems that IRB in some instances doesn't interactively support the arrow keys, and double echos, though if you press the keysequence blind and then hit enter, it works despite showing the escape characters.

[headius]

IRB is unlikely to work properly within a PTY due to the jline library we normally use. I suspect this would work ok if you run with rb-readline which on JRuby will use true native descriptors and readline-equivalent operations.

@enebo We should talk about whether to make our readline be rb-readline on platforms where we can do native IO.

[headius]

Marking for 9.2 since fixing this would likely require moving away from jline.

[enebo]

@headius is there something @byteit101 could try like replace require 'readline' with some other require which loads that version? I am more thinking about just testing to see if it solves the issue and possibly as a workaround for him.

[headius]

Move readline issues to 9.3.

[headius]

This issue is only indirectly related to IRB and has been superseded by #6552, which I discovered while fixing issues in our FFI-based io-console, which I was doing to support the new IRB.