* ext/psych/lib/psych/nodes/node.rb: Make Psych::Nodes::Node

  enumerable.
* ext/psych/lib/psych/visitors/depth_first.rb: Add a depth-first
  visitor to enumerate over a YAML AST in a depth-first fashion
* test/psych/nodes/test_enumerable.rb: test for enumerating nodes
* test/psych/visitors/test_depth_first.rb: test for depth-first
  visitor

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30624 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 37 insertions, 0 deletions

diff --git a/ext/psych/lib/psych/nodes/node.rb b/ext/psych/lib/psych/nodes/node.rb
index bfd91f99ec..7c040ec463 100644
--- a/ext/psych/lib/psych/nodes/node.rb
+++ b/ext/psych/lib/psych/nodes/node.rb
@@ -6,6 +6,8 @@ module Psych
     # The base class for any Node in a YAML parse tree.  This class should
     # never be instantiated.
     class Node
+      include Enumerable
+
       # The children of this node
       attr_reader :children
 
@@ -18,6 +20,14 @@ module Psych
       end
 
       ###
+      # Iterate over each node in the tree. Yields each node to +block+ depth
+      # first.
+      def each &block
+        return enum_for :each unless block_given?
+        Visitors::DepthFirst.new(block).accept self
+      end
+
+      ###
       # Convert this node to Ruby.
       #
       # See also Psych::Visitors::ToRuby
diff --git a/ext/psych/lib/psych/visitors.rb b/ext/psych/lib/psych/visitors.rb
index 10ac4ce270..cc98b103f1 100644
--- a/ext/psych/lib/psych/visitors.rb
+++ b/ext/psych/lib/psych/visitors.rb
@@ -3,3 +3,4 @@ require 'psych/visitors/to_ruby'
 require 'psych/visitors/emitter'
 require 'psych/visitors/yaml_tree'
 require 'psych/visitors/json_tree'
+require 'psych/visitors/depth_first'
diff --git a/ext/psych/lib/psych/visitors/depth_first.rb b/ext/psych/lib/psych/visitors/depth_first.rb
new file mode 100644
index 0000000000..c6eb814ac0
--- /dev/null
+++ b/ext/psych/lib/psych/visitors/depth_first.rb
@@ -0,0 +1,26 @@
+module Psych
+  module Visitors
+    class DepthFirst < Psych::Visitors::Visitor
+      def initialize block
+        @block = block
+      end
+
+      private
+
+      def nary o
+        o.children.each { |x| visit x }
+        @block.call o
+      end
+      alias :visit_Psych_Nodes_Stream   :nary
+      alias :visit_Psych_Nodes_Document :nary
+      alias :visit_Psych_Nodes_Sequence :nary
+      alias :visit_Psych_Nodes_Mapping  :nary
+
+      def terminal o
+        @block.call o
+      end
+      alias :visit_Psych_Nodes_Scalar :terminal
+      alias :visit_Psych_Nodes_Alias  :terminal
+    end
+  end
+end