Port the Psych/Syck YAML fix from Rubygems 1.8.24

The existing Psych/Syck fix wasn't working in certain circumstances
(gem fetch XXXXX, for example), so the broader solution from
Rubygems 1.8.24 was used instead. This resolved the problem without
breaking existing tests.

lib/rubygems.rb

@@ -106,7 +106,7 @@
 module Gem
   NAME = 'SlimGems'
   GEM_NAME = 'slimgems'
-  VERSION = '1.3.9.4'
+  VERSION = '1.3.9.5'
   SlimGemsVersion = RubyGemsVersion = VERSION
 
   ##
@@ -633,24 +633,54 @@ def self.remove_prelude_paths
   ##
   # Loads YAML, preferring Psych
 
+@yaml_loaded = false
+
+  ##
+  # Loads YAML, preferring Psych
+
   def self.load_yaml
-    begin
-      require 'psych' unless ENV['TEST_SYCK']
-    rescue ::LoadError
-    ensure
-      require 'yaml'
-    end
+    return if @yaml_loaded
+
+    test_syck = ENV['TEST_SYCK']
+
+    unless test_syck
+      begin
+        gem 'psych', '~> 1.2', '>= 1.2.1'
+      rescue Gem::LoadError
+        # It's OK if the user does not have the psych gem installed.  We will
+        # attempt to require the stdlib version
+      end
 
-    # Hack to handle syck's DefaultKey bug with psych.
-    # See the note at the top of lib/rubygems/requirement.rb for
-    # why we end up defining DefaultKey more than once.
-    if !defined? YAML::Syck
-      YAML.module_eval do
-          const_set 'Syck', Module.new {
-            const_set 'DefaultKey', Class.new
-          }
+      begin
+        # Try requiring the gem version *or* stdlib version of psych.
+        require 'psych'
+      rescue ::LoadError
+        # If we can't load psych, thats fine, go on.
+      else
+        # If 'yaml' has already been required, then we have to
+        # be sure to switch it over to the newly loaded psych.
+        if defined?(YAML::ENGINE) && YAML::ENGINE.yamler != "psych"
+          YAML::ENGINE.yamler = "psych"
         end
+
+        require 'rubygems/psych_additions'
+        require 'rubygems/psych_tree'
+      end
     end
+
+    require 'yaml'
+
+    # If we're supposed to be using syck, then we may have to force
+    # activate it via the YAML::ENGINE API.
+    if test_syck and defined?(YAML::ENGINE)
+      YAML::ENGINE.yamler = "syck" unless YAML::ENGINE.syck?
+    end
+
+    # 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/psych_additions.rb

@@ -0,0 +1,9 @@
+# This exists just to satify bugs in marshal'd gemspecs that
+# contain a reference to YAML::PrivateType. We prune these out
+# in Specification._load, but if we don't have the constant, Marshal
+# blows up.
+
+module Psych
+  class PrivateType
+  end
+end

lib/rubygems/psych_tree.rb

@@ -0,0 +1,27 @@
+module Gem
+  if defined? ::Psych::Visitors
+    class NoAliasYAMLTree < Psych::Visitors::YAMLTree
+      def visit_String(str)
+        return super unless str == '=' # or whatever you want
+
+        quote = Psych::Nodes::Scalar::SINGLE_QUOTED
+        @emitter.scalar str, nil, nil, false, true, quote
+      end
+
+      # Noop this out so there are no anchors
+      def register(target, obj)
+      end
+
+      # This is ported over from the yaml_tree in 1.9.3
+      def format_time time
+        if time.utc?
+          time.strftime("%Y-%m-%d %H:%M:%S.%9N Z")
+        else
+          time.strftime("%Y-%m-%d %H:%M:%S.%9N %:z")
+        end
+      end
+
+      private :format_time
+    end
+  end
+end

lib/rubygems/requirement.rb

@@ -129,18 +129,15 @@ def hash # :nodoc:
   end
 
   def marshal_dump # :nodoc:
+    fix_syck_default_key_in_requirements
+
     [@requirements]
   end
 
   def marshal_load array # :nodoc:
     @requirements = array[0]
 
-    # Fixup the Syck DefaultKey bug
-    @requirements.each do |r|
-      if r[0].kind_of? YAML::Syck::DefaultKey
-        r[0] = "="
-      end
-    end
+    fix_syck_default_key_in_requirements
   end
 
   def prerelease?
@@ -157,7 +154,7 @@ def pretty_print q # :nodoc:
   # True if +version+ satisfies this Requirement.
 
   def satisfied_by? version
-    requirements.all? { |op, rv| OPS[op].call version, rv }
+    requirements.all? { |op, rv| (OPS[op] || OPS["="]).call version, rv }
   end
 
   def to_s # :nodoc:
@@ -167,6 +164,20 @@ def to_s # :nodoc:
   def <=> other # :nodoc:
     to_s <=> other.to_s
   end
+
+  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
+        r[0] = "="
+      end
+    end
+  end
+
 end
 
 # :stopdoc:

lib/rubygems/syck_hack.rb

@@ -0,0 +1,74 @@
+# :stopdoc:
+
+# Hack to handle syck's DefaultKey bug
+#
+# This file is always loaded AFTER either syck or psych are already
+# loaded. It then looks at what constants are available and creates
+# a consistent view on all rubys.
+#
+# All this is so that there is always a YAML::Syck::DefaultKey
+# class no matter if the full yaml library has loaded or not.
+#
+
+module YAML
+  # In newer 1.9.2, there is a Syck toplevel constant instead of it
+  # being underneith YAML. If so, reference it back under YAML as
+  # well.
+  if defined? ::Syck
+    # for tests that change YAML::ENGINE
+    # 1.8 does not support the second argument to const_defined?
+    remove_const :Syck rescue nil
+
+    Syck = ::Syck
+
+  # JRuby's "Syck" is called "Yecht"
+  elsif defined? YAML::Yecht
+    Syck = YAML::Yecht
+
+  # Otherwise, if there is no YAML::Syck, then we've got just psych
+  # loaded, so lets define a stub for DefaultKey.
+  elsif !defined? YAML::Syck
+    module Syck
+      class DefaultKey
+      end
+    end
+  end
+
+  # Now that we've got something that is always here, define #to_s
+  # so when code tries to use this, it at least just shows up like it
+  # should.
+  module Syck
+    class DefaultKey
+      remove_method :to_s rescue nil
+
+      def to_s
+        '='
+      end
+    end
+  end
+end
+
+# Sometime in the 1.9 dev cycle, the Syck constant was moved from under YAML
+# to be a toplevel constant. So gemspecs created under these versions of Syck
+# will have references to Syck::DefaultKey.
+#
+# So we need to be sure that we reference Syck at the toplevel too so that
+# we can always load these kind of gemspecs.
+#
+if !defined?(Syck)
+  Syck = YAML::Syck
+end
+
+# Now that we've got Syck setup in all the right places, store
+# a reference to the DefaultKey class inside Gem. We do this so that
+# if later on YAML, etc are redefined, we've still got a consistent
+# place to find the DefaultKey class for comparison.
+
+module Gem
+  # for tests that change YAML::ENGINE
+  remove_const :SyckDefaultKey if const_defined? :SyckDefaultKey
+
+  SyckDefaultKey = YAML::Syck::DefaultKey
+end
+
+# :startdoc: