Mail::Multibyte::Chars no longer changes the encoding of its argument

Closes #1110

CHANGELOG.rdoc

@@ -47,9 +47,8 @@ Bugs:
 * #1023 - Fix double-quoting in display names. (garethrees)
 * #1032 - Fix that comparing messages changed their raw Message-ID to their parsed message_id. (bobjflong)
 * #1074 - Fix that the first address in a list is dropped when a subsequent address has non-US-ASCII characters. (domininik)
-* #1107 - Fix Address#display_name and other formatting flip-flopping between
-encoded and decoded forms depending on whether #encoded or #decoded was called
-last. (jeremy)
+* #1107 - Fix Address#display_name and other formatting flip-flopping between encoded and decoded forms depending on whether #encoded or #decoded was called last. (jeremy)
+* #1110 - Fix that Mail::Multibyte::Chars#initialize mutated its argument by calling force_encoding on it. (jeremy)
 
 == Version 2.6.4 - Wed Mar 23 08:16 -0700 2016 Jeremy Daer <jeremydaer@gmail.com>
 

lib/mail/multibyte/chars.rb

@@ -40,7 +40,7 @@ class Chars
       if RUBY_VERSION >= "1.9"
         # Creates a new Chars instance by wrapping _string_.
         def initialize(string)
-          @wrapped_string = string
+          @wrapped_string = string.dup
           @wrapped_string.force_encoding(Encoding::UTF_8) unless @wrapped_string.frozen?
         end
       else

spec/mail/multibyte_spec.rb

@@ -14,5 +14,12 @@
     chars = Chars.new('VĚDA A VÝZKUM')
     expect(chars.downcase).to eq("věda a výzkum")
   end
-end
 
+  if 'string'.respond_to?(:force_encoding)
+    it "doesn't mutate input string encoding" do
+      s = "ascii".force_encoding(Encoding::US_ASCII)
+      chars = Chars.new(s)
+      expect(s.encoding).to eq(Encoding::US_ASCII)
+    end
+  end
+end