Fix for subject lines with invalid UTF-8 as the last character

This seems to be the bug mentioned here:

  http://po-ru.com/diary/fixing-invalid-utf-8-in-ruby-revisited/

That explains that some versions of Iconv don't ignore
invalid characters when converting to UTF-8 even with
//IGNORE if that invalid character happens to be at the end
of the string.  In fact, as Matthew Somerville pointed out,
with some versions of iconv (e.g. 1.14 on Mac OS, apparently)
it's necessary to add and remove more than one space at the end,
in case the first character of the byte sequence indicates a
long sequence.  We add and remove 4 to be on the safe side.

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/mail_handler/backends/mail_extensions.rb b/lib/mail_handler/backends/mail_extensions.rb
index d25012e39..54599639b 100644
--- a/lib/mail_handler/backends/mail_extensions.rb
+++ b/lib/mail_handler/backends/mail_extensions.rb
@@ -73,7 +73,12 @@ module Mail
             if match
                 encoding = match[1]
                 str = Ruby18.decode_base64(match[2])
-                str = Iconv.conv('UTF-8//IGNORE', fix_encoding(encoding), str)
+                # Adding and removing trailing spaces is a workaround
+                # for Iconv.conv throwing an exception if it finds an
+                # invalid character at the end of the string, even
+                # with UTF-8//IGNORE:
+                # http://po-ru.com/diary/fixing-invalid-utf-8-in-ruby-revisited/
+                str = Iconv.conv('UTF-8//IGNORE', fix_encoding(encoding), str + "    ")[0...-4]
             end
             str
         end
@@ -86,7 +91,12 @@ module Mail
               # Remove trailing = if it exists in a Q encoding
               string = string.sub(/\=$/, '')
               str = Encodings::QuotedPrintable.decode(string)
-              str = Iconv.conv('UTF-8//IGNORE', fix_encoding(encoding), str)
+              # Adding and removing trailing spaces is a workaround
+              # for Iconv.conv throwing an exception if it finds an
+              # invalid character at the end of the string, even
+              # with UTF-8//IGNORE:
+              # http://po-ru.com/diary/fixing-invalid-utf-8-in-ruby-revisited/
+              str = Iconv.conv('UTF-8//IGNORE', fix_encoding(encoding), str + "    ")[0...-4]
           end
           str
         end