irb_debugger - Debugging with IRB on Ruby 1.9.x, no extra gems required!

irb_debugger.rb

# irb_debugger - A very simple debugger based on IRB
#
# As long as ruby-debug19 is broken, you can put this in your lib folder
# and require it in your test.rb or development.rb files.
# This will enable you to start an IRB session within your application,
# wherever you need it! Just write
#
# irb_debugger {}
#
# and it will fire IRB with full access to the current binding, i.e.
# all variables etc. will be present. Just remember the block is essential!

require 'irb'

module IRB
  def self.start_debug_session(debug_binding)
    unless @__initialized
      args = ARGV
      ARGV.replace(ARGV.dup)
      Kernel.silence_warnings { IRB.setup(nil) }
      ARGV.replace(args)
      @__initialized = true
    end

    file = debug_binding.eval('__FILE__')
    line = debug_binding.eval('__LINE__')
    if File.exist?(file)
      start = [0, line - 5].max
      lines = File.readlines(file)[start..(line + 5)]
      width = Math.log10((start + 10)).to_i
      format = "%0#{width}u"
      puts "\nIn file #{file}:"
      lines.each_with_index do |code, idx|
        arrow = line == start + idx + 1 ? '-> ' : '   '
        puts "#{arrow}#{format % (idx + start)}: #{code.rstrip}"
      end
      puts ''
    end
    workspace = WorkSpace.new(debug_binding)

    irb = Irb.new(workspace)

    @CONF[:IRB_RC].call(irb.context) if @CONF[:IRB_RC]
    @CONF[:MAIN_CONTEXT] = irb.context

    catch(:IRB_EXIT) do
      irb.eval_input
    end
  end
end

module Kernel
  def irb_debugger(&block)
    if block_given?
      IRB.start_debug_session(block.binding)
    else
      puts 'No block given! USAGE: irb_debugger {}'
    end
  end
end