* ext/psych/lib/psych.rb (parse_stream, load_stream): if a block is

  given, documents will be yielded to the block as they are parsed.
  [ruby-core:42404] [Bug #5978]

* ext/psych/lib/psych/handlers/document_stream.rb: add a handler that
  yields documents as they are parsed

* test/psych/test_stream.rb: corresponding tests.

2 files changed, 56 insertions, 6 deletions

diff --git a/lib/psych.rb b/lib/psych.rb
index cb5c4a5..69f3a7c 100644
--- a/lib/psych.rb
+++ b/lib/psych.rb
@@ -13,6 +13,7 @@ require 'psych/deprecated'
 require 'psych/stream'
 require 'psych/json/tree_builder'
 require 'psych/json/stream'
+require 'psych/handlers/document_stream'
 
 ###
 # = Overview
@@ -173,12 +174,19 @@ module Psych
   # +filename+ is used in the exception message if a Psych::SyntaxError is
   # raised.
   #
+  # If a block is given, a Psych::Nodes::Document node will be yielded to the
+  # block as it's being parsed.
+  #
   # Raises a Psych::SyntaxError when a YAML syntax error is detected.
   #
   # Example:
   #
   #   Psych.parse_stream("---\n - a\n - b") # => #<Psych::Nodes::Stream:0x00>
   #
+  #   Psych.parse_stream("--- a\n--- b") do |node|
+  #     node # => #<Psych::Nodes::Document:0x00>
+  #   end
+  #
   #   begin
   #     Psych.parse_stream("--- `", "file.txt")
   #   rescue Psych::SyntaxError => ex
@@ -187,10 +195,15 @@ module Psych
   #   end
   #
   # See Psych::Nodes for more information about YAML AST.
-  def self.parse_stream yaml, filename = nil
-    parser = self.parser
-    parser.parse yaml, filename
-    parser.handler.root
+  def self.parse_stream yaml, filename = nil, &block
+    if block_given?
+      parser = Psych::Parser.new(Handlers::DocumentStream.new(&block))
+      parser.parse yaml, filename
+    else
+      parser = self.parser
+      parser.parse yaml, filename
+      parser.handler.root
+    end
   end
 
   ###
@@ -252,12 +265,27 @@ module Psych
 
   ###
   # Load multiple documents given in +yaml+.  Returns the parsed documents
-  # as a list.  For example:
+  # as a list.  If a block is given, each document will be converted to ruby
+  # and passed to the block during parsing
+  #
+  # Example:
   #
   #   Psych.load_stream("--- foo\n...\n--- bar\n...") # => ['foo', 'bar']
   #
+  #   list = []
+  #   Psych.load_stream("--- foo\n...\n--- bar\n...") do |ruby|
+  #     list << ruby
+  #   end
+  #   list # => ['foo', 'bar']
+  #
   def self.load_stream yaml, filename = nil
-    parse_stream(yaml, filename).children.map { |child| child.to_ruby }
+    if block_given?
+      parse_stream(yaml, filename) do |node|
+        yield node.to_ruby
+      end
+    else
+      parse_stream(yaml, filename).children.map { |child| child.to_ruby }
+    end
   end
 
   ###
diff --git a/lib/psych/handlers/document_stream.rb b/lib/psych/handlers/document_stream.rb
new file mode 100644
index 0000000..e429993
--- /dev/null
+++ b/lib/psych/handlers/document_stream.rb
@@ -0,0 +1,22 @@
+require 'psych/tree_builder'
+
+module Psych
+  module Handlers
+    class DocumentStream < Psych::TreeBuilder # :nodoc:
+      def initialize &block
+        super
+        @block = block
+      end
+
+      def start_document version, tag_directives, implicit
+        n = Nodes::Document.new version, tag_directives, implicit
+        push n
+      end
+
+      def end_document implicit_end = !streaming?
+        @last.implicit_end = implicit_end
+        @block.call pop
+      end
+    end
+  end
+end