* ext/psych/lib/psych/nodes/node.rb: default to_yaml encoding to be

  UTF-8.
* test/psych/test_encoding.rb: test yaml dump encoding.

CHANGELOG.rdoc

@@ -1,3 +1,9 @@
+Thu Aug 25 06:11:35 2011  Aaron Patterson <aaron@tenderlovemaking.com>
+
+	* ext/psych/lib/psych/nodes/node.rb: default `to_yaml` encoding to be
+	  UTF-8.
+	* test/psych/test_encoding.rb: test yaml dump encoding.
+
 Wed Jun 22 03:20:52 2011  Aaron Patterson <aaron@tenderlovemaking.com>
 
 	* ext/psych/lib/psych/visitors/to_ruby.rb: Fix cyclic references of

lib/psych/nodes/node.rb

@@ -41,7 +41,7 @@ def to_ruby
       #
       # See also Psych::Visitors::Emitter
       def to_yaml io = nil, options = {}
-        real_io = io || StringIO.new
+        real_io = io || StringIO.new(''.encode('utf-8'))
 
         Visitors::Emitter.new(real_io, options).accept self
         return real_io.string unless io

test/psych/test_encoding.rb

@@ -40,6 +40,22 @@ def test_emit_alias
       assert_match(/alias value/, e.message)
     end
 
+    def test_to_yaml_is_valid
+      ext_before = Encoding.default_external
+      int_before = Encoding.default_internal
+
+      Encoding.default_external = Encoding::US_ASCII
+      Encoding.default_internal = nil
+
+      s = "こんにちは！"
+      # If no encoding is specified, use UTF-8
+      assert_equal Encoding::UTF_8, Psych.dump(s).encoding
+      assert_equal s, Psych.load(Psych.dump(s))
+    ensure
+      Encoding.default_external = ext_before
+      Encoding.default_internal = int_before
+    end
+
     def test_start_mapping
       foo = 'foo'
       bar = 'バー'