Import RubyGems trunk revision 1493.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13862 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/custom_require.rb

@@ -0,0 +1,38 @@
+#--
+# 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 =~ /\A[Nn]o such file to load -- #{Regexp.escape path}\z/ and
+       spec = Gem.searcher.find(path) then
+      Gem.activate(spec.name, false, "= #{spec.version}")
+      gem_original_require path
+    else
+      raise load_error
+    end
+  end
+end  # module Kernel
+