From dc22968239d57dddbfb5ef33ff07d013e7518611 Mon Sep 17 00:00:00 2001
From: tenderlove <tenderlove@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Mon, 18 Jul 2011 04:38:37 +0000
Subject: * ext/psych/lib/psych.rb: define a new BadAlias error class. *
 ext/psych/lib/psych/visitors/to_ruby.rb: raise an exception when  
 deserializing an alias that does not exist. * test/psych/test_merge_keys.rb:
 corresponding test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32578 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog                               | 9 +++++++++
 ext/psych/lib/psych.rb                  | 3 +++
 ext/psych/lib/psych/visitors/to_ruby.rb | 2 +-
 test/psych/test_merge_keys.rb           | 9 +++++++++
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 89168937b6..c59cbeb1df 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Mon Jul 18 13:36:47 2011  Aaron Patterson <aaron@tenderlovemaking.com>
+
+	* ext/psych/lib/psych.rb: define a new BadAlias error class.
+
+	* ext/psych/lib/psych/visitors/to_ruby.rb: raise an exception when
+	  deserializing an alias that does not exist.
+
+	* test/psych/test_merge_keys.rb: corresponding test.
+
 Mon Jul 18 00:00:46 2011  Shugo Maeda  <shugo@ruby-lang.org>
 
 	* ext/curses/curses.c: added the new class Curses::Pad, which
diff --git a/ext/psych/lib/psych.rb b/ext/psych/lib/psych.rb
index 31d73c1f03..8a4d63a49c 100644
--- a/ext/psych/lib/psych.rb
+++ b/ext/psych/lib/psych.rb
@@ -98,6 +98,9 @@ module Psych
   class Exception < RuntimeError
   end
 
+  class BadAlias < Exception
+  end
+
   autoload :Stream, 'psych/stream'
 
   ###
diff --git a/ext/psych/lib/psych/visitors/to_ruby.rb b/ext/psych/lib/psych/visitors/to_ruby.rb
index b8eb698754..fd899f65a6 100644
--- a/ext/psych/lib/psych/visitors/to_ruby.rb
+++ b/ext/psych/lib/psych/visitors/to_ruby.rb
@@ -201,7 +201,7 @@ module Psych
       end
 
       def visit_Psych_Nodes_Alias o
-        @st[o.anchor]
+        @st.fetch(o.anchor) { raise BadAlias, "Unknown alias: #{o.anchor}" }
       end
 
       private
diff --git a/test/psych/test_merge_keys.rb b/test/psych/test_merge_keys.rb
index b3ebe9b463..bf5968ff86 100644
--- a/test/psych/test_merge_keys.rb
+++ b/test/psych/test_merge_keys.rb
@@ -2,6 +2,15 @@ require 'psych/helper'
 
 module Psych
   class TestMergeKeys < TestCase
+    def test_missing_merge_key
+      yaml = <<-eoyml
+bar:
+  << : *foo
+      eoyml
+      exp = assert_raises(Psych::BadAlias) { Psych.load yaml }
+      assert_match 'foo', exp.message
+    end
+
     # [ruby-core:34679]
     def test_merge_key
       yaml = <<-eoyml
-- 
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