Why does irb insert control characters into my reverse-interactive-search buffer?

Question

If I do a reverse interactive search in irb and then enter a control character (arrow keys are the only ones I've seen this with actually). So I start with this session:

$ irb
>> print "hello"
hello

then enter ^r, h

$ irb
>> print "hello"
hello
(reverse-i-search)`he': print "hello"

So far so good. Then I hit the left arrow, and I end up with this:

$ irb
>> print "hello"
hello
>> print "[Dhello"

Subsequent use of the arrows moves the cursor around normally.

Answer 1

Do you have vi editing mode enabled?

~  $ irb
1.9.3p392 :001 > Readline.vi_editing_mode?
  => true

I had it turned on in my $HOME/.inputrc file via set editing-mode vi. Disabling it "fixed" my arrow-keys.

As mentioned by @JoLiss, other readline programs (bash, etc.) were also working correctly; so AFAICT, it's a Ruby problem. See: http://bugs.ruby-lang.org/issues/7859#change-36333

Answer 2

This won't solve your problem, but at least I can answer the question you asked (the Why):

The left arrow gets entered into the terminal as three characters, ESC, [, and D. (You can test this by typing read and pressing the left arrow, which displays ^[[D, where ^[ is how the escape character gets rendered.)

Somehow irb picks up the ESC character when it shouldn't; so ESC ends the history search, and [D gets entered literally. Looking at other programs using readline, Bash and Python behave correctly, but ledit (yeah, obscure -- sorry ^^) is having this problem as well.

Unless someone knows a solution for this, the only workaround I can think of is pressing ESC instead of an arrow key to exit history search. Or hitting enter if you don't need to edit further, of course.