why does pry history keep cloberring irb history? - ruby

Question

When I'm using pry, the history of pry keeps overwriting my irb history and it is very annoying. If i'm using pry, i'd like to see pry history and if i'm using irb, i'd like to see irb history. Is there an obvious problem in my configuration?
~/.irbrc looks like
IRB.conf[:AUTO_INDENT] = true
IRB.conf[:USE_READLINE] = true
IRB.conf[:LOAD_MODULES] = [] unless IRB.conf.key?(:LOAD_MODULES)
unless IRB.conf[:LOAD_MODULES].include?('irb/completion')
IRB.conf[:LOAD_MODULES] << 'irb/completion'
end
IRB.conf[:SAVE_HISTORY] = 1000
my .pryrc file is empty, which based on docs indicates to me that pry should be using .pry_history, which appears to be happening.
/etc/irbrc looks like
# Some default enhancements/settings for IRB, based on
# http://wiki.rubygarden.org/Ruby/page/show/Irb/TipsAndTricks
unless defined? ETC_IRBRC_LOADED
# Require RubyGems by default.
require 'rubygems'
# Activate auto-completion.
require 'irb/completion'
# Use the simple prompt if possible.
IRB.conf[:PROMPT_MODE] = :SIMPLE if IRB.conf[:PROMPT_MODE] == :DEFAULT
# Setup permanent history.
HISTFILE = "~/.irb_history"
MAXHISTSIZE = 100
begin
histfile = File::expand_path(HISTFILE)
if File::exists?(histfile)
lines = IO::readlines(histfile).collect { |line| line.chomp }
puts "Read #{lines.nitems} saved history commands from '#{histfile}'." if $VERBOSE
Readline::HISTORY.push(*lines)
else
puts "History file '#{histfile}' was empty or non-existant." if $VERBOSE
end
Kernel::at_exit do
lines = Readline::HISTORY.to_a.reverse.uniq.reverse
lines = lines[-MAXHISTSIZE, MAXHISTSIZE] if lines.nitems > MAXHISTSIZE
puts "Saving #{lines.length} history lines to '#{histfile}'." if $VERBOSE
File::open(histfile, File::WRONLY|File::CREAT|File::TRUNC) { |io| io.puts lines.join("\n") }
end
rescue => e
puts "Error when configuring permanent history: #{e}" if $VERBOSE
end
ETC_IRBRC_LOADED=true
end

Answer 1

Why the problem happens
Both Pry and IRB write their histories to Readline::HISTORY. When you enter Pry from IRB (or rails console) you have all your IRB history already in Readline::HISTORY. Pry then loads its history on top of that. When you exit Pry Readline::HISTORY isn't changed so you end up back in IRB with all of Pry's history appending to IRB's history. Finally, when you exit IRB it writes the history including Pry's to IRB's history file thus clobbering it.
Current state of the issue
I did some searching and found this is a known issue with Pry. I was also really interested in the problem so I managed to work up a solution that is awaiting a pull request review.
Workaround until merged
If you'd like to try it out before it get's merged you can grab the version from the branch I made on my fork of Pry. You can find it at https://github.com/agrberg/pry under branch save_irb_history_and_replace_on_close. If you use bundler all you need to do is add or update your line for pry to:
gem 'pry', git: 'git#github.com:agrberg/pry.git', branch: 'save_irb_history_and_replace_on_close'