Correctly handle offsets in Multibyte::Chars#index and #rindex.

The offset in codepoints was being passed directly to the wrapped string's index/rindex method. Now we translate the offset into bytes first.

[#3028 state:committed]

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index 3c16999e43..64a35dca40 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -206,7 +206,8 @@ module ActiveSupport #:nodoc:
       #   'Café périferôl'.mb_chars.index('ô') #=> 12
       #   'Café périferôl'.mb_chars.index(/\w/u) #=> 0
       def index(needle, offset=0)
-        index = @wrapped_string.index(needle, offset)
+        wrapped_offset = self.first(offset).wrapped_string.length
+        index = @wrapped_string.index(needle, wrapped_offset)
         index ? (self.class.u_unpack(@wrapped_string.slice(0...index)).size) : nil
       end
 
@@ -215,11 +216,12 @@ module ActiveSupport #:nodoc:
       # string. Returns +nil+ if _needle_ isn't found.
       #
       # Example:
-      #   'Café périferôl'.mb_chars.rindex('é') #=> 5
+      #   'Café périferôl'.mb_chars.rindex('é') #=> 6
       #   'Café périferôl'.mb_chars.rindex(/\w/u) #=> 13
       def rindex(needle, offset=nil)
         offset ||= length
-        index = @wrapped_string.rindex(needle, offset)
+        wrapped_offset = self.first(offset).wrapped_string.length
+        index = @wrapped_string.rindex(needle, wrapped_offset)
         index ? (self.class.u_unpack(@wrapped_string.slice(0...index)).size) : nil
       end