Make sure our YAML workarounds are loaded properly. Fixes rubygems#250.

lib/rubygems.rb

@@ -639,10 +639,14 @@ def self.load_path_insert_index
     index
   end
 
+  @yaml_loaded = false
+
   ##
   # Loads YAML, preferring Psych
 
   def self.load_yaml
+    return if @yaml_loaded
+
     begin
       gem 'psych', '~> 1.2', '>= 1.2.1' unless ENV['TEST_SYCK']
     rescue Gem::LoadError
@@ -661,6 +665,8 @@ def self.load_yaml
     # Now that we're sure some kind of yaml library is loaded, pull
     # in our hack to deal with Syck's DefaultKey ugliness.
     require 'rubygems/syck_hack'
+
+    @yaml_loaded = true
   end
 
   ##

lib/rubygems/requirement.rb

@@ -4,6 +4,19 @@
 # A Requirement is a set of one or more version restrictions. It supports a
 # few (<tt>=, !=, >, <, >=, <=, ~></tt>) different restriction operators.
 
+# REFACTOR: The fact that a requirement is singular or plural is kind of
+# awkward. Is Requirement the right name for this? Or should it be one
+# [op, number] pair, and we call the list of requirements something else?
+# Since a Requirement is held by a Dependency, maybe this should be made
+# singular and the list aspect should be pulled up into Dependency?
+
+require "rubygems/version"
+require "rubygems/deprecate"
+
+# If we're being loaded after yaml was already required, then
+# load our yaml + workarounds now.
+Gem.load_yaml if defined? ::YAML
+
 class Gem::Requirement
   include Comparable
 
@@ -174,6 +187,8 @@ def <=> other # :nodoc:
   private
 
   def fix_syck_default_key_in_requirements
+    Gem.load_yaml
+
     # Fixup the Syck DefaultKey bug
     @requirements.each do |r|
       if r[0].kind_of? Gem::SyckDefaultKey

lib/rubygems/specification.rb

@@ -484,6 +484,8 @@ def self.find_in_unresolved_tree path
   # +input+ can be anything that YAML.load() accepts: String or IO.
 
   def self.from_yaml(input)
+    Gem.load_yaml
+
     input = normalize_yaml_input input
     spec = YAML.load input