Avoid overwriting irb history with pry (when opening a pry session inside an existing irb session)

.pryrc

require 'readline'

def __flush_history
  Readline::HISTORY.slice!(0..-1)
end

def __restore_history(irb_history)
  __flush_history
  irb_history.each { |line| Readline::HISTORY << line }
end

# pry initializes its history from the file before the before_session hook
#  is called, so we must collect the history before that
__irb_history = __flush_history # rubocop:disable Lint/UnderscorePrefixedVariableName
Pry.config.history_file = '~/.pry_history'

Pry.config.hooks.add_hook(:before_session, :trigger_save_irb_history) do
  __irb_history = __flush_history if __irb_history.nil?
  Pry.history.load # reload the pry history from file
end

Pry.config.hooks.add_hook(:after_session, :trigger_restore_irb_history) do
  __restore_history(__irb_history)
  __irb_history = nil
end