gist.rb

require 'rubygems' unless defined?(Gem)

# load a gem/lib into irb in a way that is durable to bundler LOAD_PATH
# hackery
#
# inspired by
#   https://github.com/aniero/dotfiles/blob/master/irbrc#L4-35
#
# IRB.gem('irbcp')
# IRB.gem('awesome_print', :lib => 'ap')
#
  def IRB.gem(name, options = {})
    name = name.to_s
    lib = (options[:lib] || options['lib'] || name).to_s

    require(lib)
  rescue LoadError => e
    candidates = []

    glob = File.join(Config::CONFIG['libdir'], "ruby/gems/*")

    system_gem_paths = Dir[glob]
    gem_paths = Gem.path

    paths = gem_paths + system_gem_paths 

    paths.each do |path|
      glob = File.join(path, 'gems/*-[0-9].[0-9].[0-9]') 

      Dir.glob(glob) do |entry|
        basename = File.basename(entry)
        gemname, version = basename.split(/-/, 2)

        if gemname == name
          libdir = File.expand_path(File.join(entry, 'lib'))
          class << libdir; attr_accessor(:gemname);  attr_accessor(:version); end
          libdir.gemname = gemname
          libdir.version = version.scan(/\d+/).map{|digit| digit.to_i}
          candidates.push(libdir)
        end
      end
    end

    raise if candidates.empty?
    candidates.sort!{|a,b| a.version <=> b.version}
    libdir = candidates.last

    begin
      $LOAD_PATH.unshift(libdir)
      require(lib)
    ensure
      $LOAD_PATH.shift()
    end
  end