Re-support class based xgettext parser add API

GitHub: fix mutoh#10

Suggested by Michael Grosser. Thanks!!!

Author: kou

lib/gettext/tools/xgettext.rb

@@ -31,12 +31,23 @@ class << self
         def run(*arguments)
           new.run(*arguments)
         end
+
+        # Adds a parser to the default parser list.
+        #
+        # @param (see #add_parser)
+        # @return [void]
+        #
+        # @see #add_parser
+        def add_parser(parser)
+          @@default_parsers.unshift(parser)
+        end
       end
 
       include GetText
 
       bindtextdomain("rgettext")
 
+      # @api private
       @@default_parsers = []
       builtin_parser_info_list = [
         ["glade", "GladeParser"],
@@ -66,10 +77,10 @@ def initialize #:nodoc:
         @copyright_holder = nil
       end
 
-      # How to add your option parser
       # The option parser module requires to have target?(file) and
       # parser(file, ary) method.
       #
+      # @example How to add your option parser
       #  require "gettext/tools/xgettext"
       #  module FooParser
       #    module_function
@@ -109,8 +120,14 @@ def initialize #:nodoc:
       #  end
       #
       #  GetText::XGetText.add_parser(FooParser)
-      def add_parser(klass)
-        @parsers.insert(0, klass)
+      #
+      # @param [#target?, #parse] parser
+      #   It parses target file and extracts translate target messages from the
+      #   target file. If there are multiple target files, parser.parse is
+      #   called multiple times.
+      # @return [void]
+      def add_parser(parser)
+        @parsers.insert(0, parser)
       end
 
       def generate_pot_header # :nodoc:
@@ -156,7 +173,8 @@ def parse(paths) # :nodoc:
             @parsers.each do |klass|
               next unless klass.target?(path)
 
-              if klass.method(:parse).arity == 1
+              parse_method = klass.method(:parse)
+              if parse_method.arity == 1 or parse_method.arity == -1
                 targets = klass.parse(path)
               else
                 # For backward compatibility

test/tools/test_xgettext.rb

@@ -119,6 +119,41 @@ def test_copyright_holder
     end
   end
 
+  class TestAddParser < self
+    setup
+    def setup_default_parsers
+      @default_parsers = default_parsers.dup
+    end
+
+    teardown
+    def teardown_default_parsers
+      default_parsers.replace(@default_parsers)
+    end
+
+    def test_class_method
+      GetText::Tools::XGetText.add_parser(mock_html_parser)
+      xgettext = GetText::Tools::XGetText.new
+      xgettext.parse(["index.html"])
+    end
+
+    def test_instance_method
+      @xgettext.add_parser(mock_html_parser)
+      @xgettext.parse(["index.html"])
+    end
+
+    private
+    def default_parsers
+      GetText::Tools::XGetText.module_eval("@@default_parsers")
+    end
+
+    def mock_html_parser
+      html_parser = Object.new
+      mock(html_parser).target?("index.html") {true}
+      mock(html_parser).parse("index.html") {[]}
+      html_parser
+    end
+  end
+
   private
   def header(options=nil)
     options ||= {}