Rails Console output breaks when modifying - ruby-on-rails

Question

Totally lacking intuition here.
First i thought i only happens when copying and pasting code from editor. Unfortunately it's more common. Only thing I am doing is trying to insert more code somewhere in the middle of current input or modifying it.
Expected behavior:
Modify input without side effects.
What actually happens:
VERY OFTEN when modifying input it gets messed up.
If that happens every key press will copy and insert current input alongside with pressed character.
Vital notes:
Encoding is set to UTF-8 in terminal(s)
Issue persists on different emulators ( Terminator, gnome-terminal )
Issue persists when using different Ruby runtime console ( IRB, Pry )
Issue appears to be related to Ruby runtime, NOT Linux shell (i guess...)
Issue appears since:
Since system install. Didn't appear on my MacBook Air
System:
ArchLinux, although coworker reported same thing happens on his MacBook Pro.
How to reproduce (works for me):
Open rails console
Type example code: Shift.where(name: "som").where(name: "dom").where(name: "pom")
Navigate cursor to modify first where statement.
Change "som" to "SOM"
Should see it break
Press random key repeatedly to see it break even more.
Images:
Good input
Now i will navigate to first where statement to change "som" to uppercase "SOM"
I basically navigated my cursor and pressed SHIFT+S, SHIFT+O, SHIFT+M
Hope it's clear enough :-)
Thank you!
EDIT 1:
Tried using zsh instead of bash, didn't help
Disabled spring gem, didn't help
EDIT 2:
Folks on reddit suggested that i should check if there are any Ruby readline warnings eg. "Readline is not installed". None of them appear anywhere. Also reinstalled ruby 2.4.1, seems like it's not the problem in my case.
EDIT 3:
I cannot reproduce the issue in a different Rails project.
Issue appears on Rails 5.1.1, meanwhile 5.0.3 works flawlessly.
Is it possible that Rails itself (or rather one of its gems) can be the cause?

Answer 1

I had a very similar issue, and I boiled it down to my coloring.
I had the following in my IRBRC:
class String
def _colorize(color_code)
"\e[#{color_code}m#{self}\e[0m"
end
def red
_colorize(31)
end
def yellow
_colorize(33)
end
end
IRB.conf[:PROMPT][:MY_PROMPT] = {
:AUTO_INDENT => true, # enables auto-indent mode
:PROMPT_I => "[ME]".red + " > ".yellow, # normal prompt
:PROMPT_S => "[ME]".red + " ".yellow, # prompt for continuated strings
:PROMPT_C => "[ME]".red + " * ".yellow, # prompt for continuated statement
:RETURN => "[ME]".red + "=> ".yellow + "%s\n".red # format to return value
}
IRB.conf[:PROMPT_MODE] = :MY_PROMPT
And when I removed the .red and .yellow, everything was just fine.
I think it's because my coloring characters like \e[31m was getting counted as a length 5 characters instead of 0 characters.
My solution was to remove my coloring for the time being. Hopefully someone will come up with a better solution than that.