ruby--ruby/lib/rubygems/custom_require.rb

#--
# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
# All rights reserved.
# See LICENSE.txt for permissions.
#++

require 'rubygems'

module Kernel
  alias gem_original_require require # :nodoc:

  #
  # We replace Ruby's require with our own, which is capable of
  # loading gems on demand.
  #
  # When you call <tt>require 'x'</tt>, this is what happens:
  # * If the file can be loaded from the existing Ruby loadpath, it
  #   is.
  # * Otherwise, installed gems are searched for a file that matches.
  #   If it's found in gem 'y', that gem is activated (added to the
  #   loadpath).
  #
  # The normal <tt>require</tt> functionality of returning false if
  # that file has already been loaded is preserved.
  #
  def require(path) # :nodoc:
    gem_original_require path
  rescue LoadError => load_error
    if load_error.message =~ /#{Regexp.escape path}\z/ and
       spec = Gem.searcher.find(path) then
      Gem.activate(spec.name, "= #{spec.version}")
      gem_original_require path
    else
      raise load_error
    end
  end
end  # module Kernel