Work around inconsistent encoding result from String#gsub! in #expand_tabs

Author: drbrain

History.txt

@@ -4,8 +4,8 @@
   * When including a file lossily force-transcode it to the output encoding
     instead of crashing to preserve as much content as possible.  Ruby Bug
     #4376 by Yui NARUSE.
-  * Work around inconsistent encoding result from String#sub!.  Related to
-    Ruby Bug #4376.
+  * Work around inconsistent encoding result from String#sub!, String#gsub!.
+    Related to Ruby Bug #4376.
   * Work around inconsistent encoding result from String#[]=.  Related to Ruby
     Bug #4376.
   * When Darkfish fails the file being generated is now reported.

lib/rdoc/text.rb

@@ -44,9 +44,12 @@ def self.encode_fallback character, encoding, fallback
   def expand_tabs text
     expanded = []
 
+    space = ' '
+    space.force_encoding text.encoding if Object.const_defined? :Encoding
+
     text.each_line do |line|
       line.gsub!(/^(.{8}*?)([^\t\r\n]{0,7})\t/) do
-        "#{$1}#{$2}#{' ' * (8 - $2.size)}"
+        "#{$1}#{$2}#{space * (8 - $2.size)}"
       end until line !~ /\t/
 
       expanded << line

test/test_rdoc_text.rb

@@ -55,6 +55,18 @@ def test_expand_tabs
                  expand_tabs(".\t\t."), 'dot tab tab dot')
   end
 
+  def test_expand_tabs_encoding
+    skip "Encoding not implemented" unless Object.const_defined? :Encoding
+
+    inn = "hello\ns\tdave"
+    inn.force_encoding Encoding::BINARY
+
+    out = expand_tabs inn
+
+    assert_equal "hello\ns       dave", out
+    assert_equal Encoding::BINARY, out.encoding
+  end
+
   def test_flush_left
     text = <<-TEXT