7 files changed, 356 insertions, 177 deletions

diff --git a/src/mailman/app/docs/pipelines.rst b/src/mailman/app/docs/pipelines.rst
index daedab50a..dfdc6d70c 100644
--- a/src/mailman/app/docs/pipelines.rst
+++ b/src/mailman/app/docs/pipelines.rst
@@ -45,9 +45,9 @@ etc.
     To: test@example.com
     Message-ID: <first>
     X-Message-ID-Hash: 4CMWUN6BHVCMHMDAOSJZ2Q72G5M32MWB
-    Subject: [Test] My first post
     X-Mailman-Version: ...
     Precedence: list
+    Subject: [Test] My first post
     List-Id: <test.example.com>
     Archived-At: http://lists.example.com/.../4CMWUN6BHVCMHMDAOSJZ2Q72G5M32MWB
     List-Archive: <http://lists.example.com/archives/test@example.com>
@@ -84,9 +84,9 @@ processing queues.
     To: test@example.com
     Message-ID: <first>
     X-Message-ID-Hash: 4CMWUN6BHVCMHMDAOSJZ2Q72G5M32MWB
-    Subject: [Test] My first post
     X-Mailman-Version: ...
     Precedence: list
+    Subject: [Test] My first post
     List-Id: <test.example.com>
     ...
     <BLANKLINE>
@@ -121,9 +121,9 @@ delivered to end recipients.
     To: test@example.com
     Message-ID: <first>
     X-Message-ID-Hash: 4CMWUN6BHVCMHMDAOSJZ2Q72G5M32MWB
-    Subject: [Test] My first post
     X-Mailman-Version: ...
     Precedence: list
+    Subject: [Test] My first post
     List-Id: <test.example.com>
     ...
     <BLANKLINE>
@@ -152,9 +152,9 @@ There's now one message in the digest mailbox, getting ready to be sent.
     To: test@example.com
     Message-ID: <first>
     X-Message-ID-Hash: 4CMWUN6BHVCMHMDAOSJZ2Q72G5M32MWB
-    Subject: [Test] My first post
     X-Mailman-Version: ...
     Precedence: list
+    Subject: [Test] My first post
     List-Id: <test.example.com>
     ...
     <BLANKLINE>
diff --git a/src/mailman/core/pipelines.py b/src/mailman/core/pipelines.py
index e164169a4..5fdba8358 100644
--- a/src/mailman/core/pipelines.py
+++ b/src/mailman/core/pipelines.py
@@ -120,6 +120,7 @@ class PostingPipeline(BasePipeline):
         'cleanse',
         'cleanse-dkim',
         'cook-headers',
+        'subject-prefix',
         'rfc-2369',
         'to-archive',
         'to-digest',
diff --git a/src/mailman/handlers/cook_headers.py b/src/mailman/handlers/cook_headers.py
index 1ab527bb4..f37e8f0e2 100644
--- a/src/mailman/handlers/cook_headers.py
+++ b/src/mailman/handlers/cook_headers.py
@@ -27,8 +27,7 @@ __all__ = [
 
 import re
 
-from email.errors import HeaderParseError
-from email.header import Header, decode_header, make_header
+from email.header import Header
 from email.utils import parseaddr, formataddr, getaddresses
 from zope.interface import implementer
 
@@ -78,13 +77,6 @@ def process(mlist, msg, msgdata):
     msgdata['original_sender'] = msg.sender
     # VirginRunner sets _fasttrack for internally crafted messages.
     fasttrack = msgdata.get('_fasttrack')
-    if not msgdata.get('isdigest') and not fasttrack:
-        try:
-            prefix_subject(mlist, msg, msgdata)
-        except (UnicodeError, ValueError):
-            # TK: Sometimes subject header is not MIME encoded for 8bit
-            # simply abort prefixing.
-            pass
     # Add Precedence: and other useful headers.  None of these are standard
     # and finding information on some of them are fairly difficult.  Some are
     # just common practice, and we'll add more here as they become necessary.
@@ -171,114 +163,6 @@ def process(mlist, msg, msgdata):
 
 
 
-def prefix_subject(mlist, msg, msgdata):
-    """Maybe add a subject prefix.
-
-    Add the subject prefix unless the message is a digest or is being fast
-    tracked (e.g. internally crafted, delivered to a single user such as the
-    list admin).
-    """
-    if not mlist.subject_prefix.strip():
-        return
-    prefix = mlist.subject_prefix
-    subject = msg.get('subject', '')
-    # Try to figure out what the continuation_ws is for the header
-    if isinstance(subject, Header):
-        lines = str(subject).splitlines()
-    else:
-        lines = subject.splitlines()
-    ws = '\t'
-    if len(lines) > 1 and lines[1] and lines[1][0] in ' \t':
-        ws = lines[1][0]
-    msgdata['original_subject'] = subject
-    # The subject may be multilingual but we take the first charset as major
-    # one and try to decode.  If it is decodable, returned subject is in one
-    # line and cset is properly set.  If fail, subject is mime-encoded and
-    # cset is set as us-ascii.  See detail for ch_oneline() (CookHeaders one
-    # line function).
-    subject, cset = ch_oneline(subject)
-    # TK: Python interpreter has evolved to be strict on ascii charset code
-    # range.  It is safe to use unicode string when manupilating header
-    # contents with re module.  It would be best to return unicode in
-    # ch_oneline() but here is temporary solution.
-    subject = subject.decode(cset)
-    # If the subject_prefix contains '%d', it is replaced with the
-    # mailing list sequential number.  Sequential number format allows
-    # '%d' or '%05d' like pattern.
-    prefix_pattern = re.escape(prefix)
-    # unescape '%' :-<
-    prefix_pattern = '%'.join(prefix_pattern.split(r'\%'))
-    p = re.compile('%\d*d')
-    if p.search(prefix, 1):
-        # prefix have number, so we should search prefix w/number in subject.
-        # Also, force new style.
-        prefix_pattern = p.sub(r'\s*\d+\s*', prefix_pattern)
-    subject = re.sub(prefix_pattern, '', subject)
-    rematch = re.match('((RE|AW|SV|VS)(\[\d+\])?:\s*)+', subject, re.I)
-    if rematch:
-        subject = subject[rematch.end():]
-        recolon = 'Re:'
-    else:
-        recolon = ''
-    # At this point, subject may become null if someone post mail with
-    # subject: [subject prefix]
-    if subject.strip() == '':
-        subject = _('(no subject)')
-        cset = mlist.preferred_language.charset
-    # and substitute %d in prefix with post_id
-    try:
-        prefix = prefix % mlist.post_id
-    except TypeError:
-        pass
-    # Get the header as a Header instance, with proper unicode conversion
-    if not recolon:
-        h = uheader(mlist, prefix, 'Subject', continuation_ws=ws)
-    else:
-        h = uheader(mlist, prefix, 'Subject', continuation_ws=ws)
-        h.append(recolon)
-    # TK: Subject is concatenated and unicode string.
-    subject = subject.encode(cset, 'replace')
-    h.append(subject, cset)
-    del msg['subject']
-    msg['Subject'] = h
-    ss = uheader(mlist, recolon, 'Subject', continuation_ws=ws)
-    ss.append(subject, cset)
-    msgdata['stripped_subject'] = ss
-
-
-
-def ch_oneline(headerstr):
-    # Decode header string in one line and convert into single charset.
-    # Return (string, cset) tuple as check for failure.
-    try:
-        d = decode_header(headerstr)
-        # At this point, we should rstrip() every string because some
-        # MUA deliberately add trailing spaces when composing return
-        # message.
-        d = [(s.rstrip(), c) for (s, c) in d]
-        # Find all charsets in the original header.  We use 'utf-8' rather
-        # than using the first charset (in mailman 2.1.x) if multiple
-        # charsets are used.
-        csets = []
-        for (s, c) in d:
-            if c and c not in csets:
-                csets.append(c)
-        if len(csets) == 0:
-            cset = 'us-ascii'
-        elif len(csets) == 1:
-            cset = csets[0]
-        else:
-            cset = 'utf-8'
-        h = make_header(d)
-        ustr = str(h)
-        oneline = ''.join(ustr.splitlines())
-        return oneline.encode(cset, 'replace'), cset
-    except (LookupError, UnicodeError, ValueError, HeaderParseError):
-        # possibly charset problem. return with undecoded string in one line.
-        return ''.join(headerstr.splitlines()), 'us-ascii'
-
-
-
 @implementer(IHandler)
 class CookHeaders:
     """Modify message headers."""
diff --git a/src/mailman/handlers/docs/subject-munging.rst b/src/mailman/handlers/docs/subject-munging.rst
index b51fedebd..de22a928c 100644
--- a/src/mailman/handlers/docs/subject-munging.rst
+++ b/src/mailman/handlers/docs/subject-munging.rst
@@ -1,44 +1,42 @@
-===============
-Subject munging
-===============
+================
+Subject prefixes
+================
 
-Messages that flow through the global pipeline get their headers *cooked*,
-which basically means that their headers go through several mostly unrelated
-transformations.  Some headers get added, others get changed.  Some of these
-changes depend on mailing list settings and others depend on how the message
-is getting sent through the system.  We'll take things one-by-one.
+Mailing lists can define a *subject prefix* which gets added to the front of
+any ``Subject`` text.  This can be used to quickly identify which mailing list
+the message was posted to.
 
     >>> mlist = create_list('test@example.com')
 
+The default list style gives the mailing list a default prefix.
 
-Inserting a prefix
-==================
+    >>> print(mlist.subject_prefix)
+    [Test]
 
-Another thing header cooking does is *munge* the ``Subject`` header by
-inserting the subject prefix for the list at the front.  If there's no subject
-header in the original message, Mailman uses a canned default.  In order to do
-subject munging, a mailing list must have a preferred language.
-::
+This can be changed to anything, but typically ends with a trailing space.
 
     >>> mlist.subject_prefix = '[XTest] '
-    >>> mlist.preferred_language = 'en'
+    >>> process = config.handlers['subject-prefix'].process
+
+
+No Subject
+==========
+
+If the original message has no ``Subject``, then a canned one is used.
+
     >>> msg = message_from_string("""\
     ... From: aperson@example.com
     ...
     ... A message of great import.
     ... """)
-    >>> msgdata = {}
-
-    >>> from mailman.handlers.cook_headers import process
-    >>> process(mlist, msg, msgdata)
-
-The original subject header is stored in the message metadata.
-
-    >>> msgdata['original_subject']
-    ''
+    >>> process(mlist, msg, {})
     >>> print(msg['subject'])
     [XTest] (no subject)
 
+
+Inserting a prefix
+==================
+
 If the original message had a ``Subject`` header, then the prefix is inserted
 at the beginning of the header's value.
 
@@ -50,34 +48,12 @@ at the beginning of the header's value.
     ... """)
     >>> msgdata = {}
     >>> process(mlist, msg, msgdata)
-    >>> print(msgdata['original_subject'])
-    Something important
     >>> print(msg['subject'])
     [XTest] Something important
 
-``Subject`` headers are not munged for digest messages.
-    
-    >>> msg = message_from_string("""\
-    ... From: aperson@example.com
-    ... Subject: Something important
-    ...
-    ... A message of great import.
-    ... """)
-    >>> process(mlist, msg, dict(isdigest=True))
-    >>> print(msg['subject'])
-    Something important
+The original ``Subject`` is available in the metadata.
 
-Nor are they munged for *fast tracked* messages, which are generally defined
-as messages that Mailman crafts internally.
-
-    >>> msg = message_from_string("""\
-    ... From: aperson@example.com
-    ... Subject: Something important
-    ...
-    ... A message of great import.
-    ... """)
-    >>> process(mlist, msg, dict(_fasttrack=True))
-    >>> print(msg['subject'])
+    >>> print(msgdata['original_subject'])
     Something important
 
 If a ``Subject`` header already has a prefix, usually following a ``Re:``
@@ -95,8 +71,7 @@ front of the header text.
     [XTest] Re: Something important
 
 If the ``Subject`` header has a prefix at the front of the header text, that's
-where it will stay.  This is called *new style* prefixing and is the only
-option available in Mailman 3.
+where it will stay.
 
     >>> msg = message_from_string("""\
     ... From: aperson@example.com
@@ -124,7 +99,7 @@ set than the encoded header.
     >>> process(mlist, msg, {})
     >>> print(msg['subject'].encode())
     [XTest] =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
-    >>> print(msg['subject'])
+    >>> print(str(msg['subject']))
     [XTest] メールマン
 
 
@@ -194,7 +169,7 @@ prefix, possibly with a different posting number.
     >>> print(msg['subject'].encode())
     [XTest 456] Re: =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
     >>> print(msg['subject'])
-    [XTest 456]  Re: メールマン
+    [XTest 456] Re: メールマン
 
 As before, old style subject prefixes are re-ordered.
 
diff --git a/src/mailman/handlers/subject_prefix.py b/src/mailman/handlers/subject_prefix.py
new file mode 100644
index 000000000..ee1921ac2
--- /dev/null
+++ b/src/mailman/handlers/subject_prefix.py
@@ -0,0 +1,187 @@
+# Copyright (C) 2014 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+# more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Subject header prefix munging."""
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+__metaclass__ = type
+__all__ = [
+    'SubjectPrefix',
+    ]
+
+
+import re
+
+from email.header import Header, make_header, decode_header
+from mailman.core.i18n import _
+from mailman.interfaces.handler import IHandler
+from zope.interface import implementer
+
+
+RE_PATTERN = '((RE|AW|SV|VS)(\[\d+\])?:\s*)+'
+ASCII_CHARSETS = (None, 'ascii', 'us-ascii')
+EMPTYSTRING = ''
+
+
+
+def ascii_header(mlist, msgdata, subject, prefix, prefix_pattern, ws):
+    if mlist.preferred_language.charset not in ASCII_CHARSETS:
+        return None
+    for chunk, charset in decode_header(subject.encode()):
+        if charset not in ASCII_CHARSETS:
+            return None
+    subject_text = EMPTYSTRING.join(str(subject).splitlines())
+    rematch = re.match(RE_PATTERN, subject_text, re.I)
+    if rematch:
+        subject_text = subject_text[rematch.end():]
+        recolon = 'Re: '
+    else:
+        recolon = ''
+    # At this point, the subject may become null if someone posted mail
+    # with "Subject: [subject prefix]".
+    if subject_text.strip() == '':
+        with _.using(mlist.preferred_language.code):
+            subject_text = _('(no subject)')
+    else:
+        subject_text = re.sub(prefix_pattern, '', subject_text)
+    msgdata['stripped_subject'] = subject_text
+    lines = subject_text.splitlines()
+    first_line = [lines[0]]
+    if recolon:
+        first_line.insert(0, recolon)
+    if prefix:
+        first_line.insert(0, prefix)
+    subject_text = EMPTYSTRING.join(first_line)
+    return Header(subject_text, continuation_ws=ws)
+
+
+def all_same_charset(mlist, msgdata, subject, prefix, prefix_pattern, ws):
+    list_charset = mlist.preferred_language.charset
+    chunks = []
+    for chunk, charset in decode_header(subject.encode()):
+        if charset is None:
+            charset = 'us-ascii'
+        chunks.append(chunk.decode(charset))
+        if charset != list_charset:
+            return None
+    subject_text = EMPTYSTRING.join(chunks)
+    rematch = re.match(RE_PATTERN, subject_text, re.I)
+    if rematch:
+        subject_text = subject_text[rematch.end():]
+        recolon = 'Re: '
+    else:
+        recolon = ''
+    # At this point, the subject may become null if someone posted mail
+    # with "Subject: [subject prefix]".
+    if subject_text.strip() == '':
+        with _.push(mlist.preferred_language.code):
+            subject_text = _('(no subject)')
+    else:
+        subject_text = re.sub(prefix_pattern, '', subject_text)
+    msgdata['stripped_subject'] = subject_text
+    lines = subject_text.splitlines()
+    first_line = [lines[0]]
+    if recolon:
+        first_line.insert(0, recolon)
+    if prefix:
+        first_line.insert(0, prefix)
+    subject_text = EMPTYSTRING.join(first_line)
+    return Header(subject_text, charset=list_charset, continuation_ws=ws)
+
+
+def mixed_charsets(mlist, msgdata, subject, prefix, prefix_pattern, ws):
+    list_charset = mlist.preferred_language.charset
+    chunks = decode_header(subject.encode())
+    if len(chunks) == 0:
+        with _.push(mlist.preferred_language.code):
+            subject_text = _('(no subject)')
+        chunks = [(prefix, list_charset),
+                  (subject_text, list_charset),
+                  ]
+        return make_header(chunks, continuation_ws=ws)
+    # Only search the first chunk for Re and existing prefix.
+    chunk_text, chunk_charset = chunks[0]
+    if chunk_charset is None:
+        chunk_charset = 'us-ascii'
+    first_text = chunk_text.decode(chunk_charset)
+    first_text = re.sub(prefix_pattern, '', first_text).lstrip()
+    rematch = re.match(RE_PATTERN, first_text, re.I)
+    if rematch:
+        first_text = 'Re: ' + first_text[rematch.end():]
+    chunks[0] = (first_text, chunk_charset)
+    # The subject text stripped of the prefix, for use in the NNTP gateway.
+    msgdata['stripped_subject'] = str(make_header(chunks, continuation_ws=ws))
+    chunks.insert(0, (prefix, list_charset))
+    return make_header(chunks, continuation_ws=ws)
+
+
+
+@implementer(IHandler)
+class SubjectPrefix:
+    """Add a list-specific prefix to the Subject header value."""
+
+    name = 'subject-prefix'
+    description = _('Add a list-specific prefix to the Subject header value.')
+
+    def process(self, mlist, msg, msgdata):
+        """See `IHandler`."""
+        if msgdata.get('isdigest') or msgdata.get('_fasttrack'):
+            return
+        prefix = mlist.subject_prefix
+        if not prefix.strip():
+            return
+        subject = msg.get('subject', '')
+        # Turn the value into a Header instance and try to figure out what
+        # continuation whitespace is being used.
+        # Save the original Subject.
+        msgdata['original_subject'] = subject
+        if isinstance(subject, Header):
+            subject_text = str(subject)
+        else:
+            subject = make_header(decode_header(subject))
+            subject_text = str(subject)
+        lines = subject_text.splitlines()
+        ws = '\t'
+        if len(lines) > 1 and lines[1] and lines[1][0] in ' \t':
+            ws = lines[1][0]
+        # If the subject_prefix contains '%d', it is replaced with the mailing
+        # list's sequence number.  The sequential number format allows '%d' or
+        # '%05d' like pattern.
+        prefix_pattern = re.escape(prefix)
+        # Unescape '%'.
+        prefix_pattern = '%'.join(prefix_pattern.split(r'\%'))
+        p = re.compile('%\d*d')
+        if p.search(prefix, 1):
+            # The prefix has number, so we should search prefix w/number in
+            # subject.  Also, force new style.
+            prefix_pattern = p.sub(r'\s*\d+\s*', prefix_pattern)
+        # Substitute %d in prefix with post_id
+        try:
+            prefix = prefix % mlist.post_id
+        except TypeError:
+            pass
+        for handler in (ascii_header,
+                        all_same_charset,
+                        mixed_charsets,
+                        ):
+            new_subject = handler(
+                mlist, msgdata, subject, prefix, prefix_pattern, ws)
+            if new_subject is not None:
+                del msg['subject']
+                msg['Subject'] = new_subject
+                return
diff --git a/src/mailman/handlers/tests/test_subject_prefix.py b/src/mailman/handlers/tests/test_subject_prefix.py
new file mode 100644
index 000000000..1125f3811
--- /dev/null
+++ b/src/mailman/handlers/tests/test_subject_prefix.py
@@ -0,0 +1,132 @@
+# Copyright (C) 2014 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+# more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Test the Subject header prefix munging.."""
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+__metaclass__ = type
+__all__ = [
+    'TestSubjectPrefix',
+    ]
+
+
+import unittest
+
+from mailman.app.lifecycle import create_list
+from mailman.config import config
+from mailman.email.message import Message
+from mailman.testing.layers import ConfigLayer
+
+
+
+class TestSubjectPrefix(unittest.TestCase):
+    layer = ConfigLayer
+
+    def setUp(self):
+        self._mlist = create_list('test@example.com')
+        self._process = config.handlers['subject-prefix'].process
+
+    def test_isdigest(self):
+        # If the message is destined for the digest, the Subject header does
+        # not get touched.
+        msg = Message()
+        msg['Subject'] = 'A test message'
+        self._process(self._mlist, msg, dict(isdigest=True))
+        self.assertEqual(str(msg['subject']), 'A test message')
+
+    def test_fasttrack(self):
+        # Messages internally crafted are 'fast tracked' and don't get their
+        # Subjects prefixed either.
+        msg = Message()
+        msg['Subject'] = 'A test message'
+        self._process(self._mlist, msg, dict(_fasttrack=True))
+        self.assertEqual(str(msg['subject']), 'A test message')
+
+    def test_whitespace_only_prefix(self):
+        # If the Subject prefix only contains whitespace, ignore it.
+        self._mlist.subject_prefix = '    '
+        msg = Message()
+        msg['Subject'] = 'A test message'
+        self._process(self._mlist, msg, dict(_fasttrack=True))
+        self.assertEqual(str(msg['subject']), 'A test message')
+
+    def test_save_original_subject(self):
+        # When the Subject gets prefixed, the original is saved in the message
+        # metadata.
+        msgdata = {}
+        msg = Message()
+        msg['Subject'] = 'A test message'
+        self._process(self._mlist, msg, msgdata)
+        self.assertEqual(msgdata['original_subject'], 'A test message')
+
+    def test_prefix(self):
+        # The Subject gets prefixed.  The prefix gets automatically set by the
+        # list style when the list gets created.
+        msg = Message()
+        msg['Subject'] = 'A test message'
+        self._process(self._mlist, msg, {})
+        self.assertEqual(str(msg['subject']), '[Test] A test message')
+
+    def test_no_double_prefix(self):
+        # Don't add a prefix if the subject already contains one.
+        msg = Message()
+        msg['Subject'] = '[Test] A test message'
+        self._process(self._mlist, msg, {})
+        self.assertEqual(str(msg['subject']), '[Test] A test message')
+
+    def test_re_prefix(self):
+        # The subject has a Re: prefix.  Make sure that gets preserved, but
+        # after the list prefix.
+        msg = Message()
+        msg['Subject'] = 'Re: [Test] A test message'
+        self._process(self._mlist, msg, {})
+        self.assertEqual(str(msg['subject']), '[Test] Re: A test message')
+
+    def test_multiline_subject(self):
+        # The subject appears on multiple lines.
+        msg = Message()
+        msg['Subject'] = '\n A test message'
+        self._process(self._mlist, msg, {})
+        self.assertEqual(str(msg['subject']), '[Test]  A test message')
+
+    def test_i18n_prefix(self):
+        # The Subject header is encoded, but the prefix is still added.
+        msg = Message()
+        msg['Subject'] = '=?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?='
+        self._process(self._mlist, msg, {})
+        subject = msg['subject']
+        self.assertEqual(subject.encode(),
+                         '[Test] =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=')
+        self.assertEqual(str(subject), '[Test] メールマン')
+
+    def test_i18n_subject_with_sequential_prefix_and_re(self):
+        # The mailing list defines a sequential prefix, and the original
+        # Subject has a prefix with a different sequence number, *and* it also
+        # contains a Re: prefix.  Make sure the sequence gets updated and all
+        # the bits get put back together in the right order.
+        self._mlist.subject_prefix = '[Test %d]'
+        self._mlist.post_id = 456
+        msg = Message()
+        msg['Subject'] = \
+          '[Test 123] Re: =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?='
+        self._process(self._mlist, msg, {})
+        subject = msg['subject']
+        self.assertEqual(
+            subject.encode(),
+            '[Test 456] Re: =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=')
+        self.assertEqual(str(subject), '[Test 456] Re: メールマン')
diff --git a/src/mailman/runners/nntp.py b/src/mailman/runners/nntp.py
index 5d0013055..d26001a57 100644
--- a/src/mailman/runners/nntp.py
+++ b/src/mailman/runners/nntp.py
@@ -111,9 +111,9 @@ def prepare_message(mlist, msg, msgdata):
         del msg['approved']
         msg['Approved'] = mlist.posting_address
     # Should we restore the original, non-prefixed subject for gatewayed
-    # messages? TK: We use stripped_subject (prefix stripped) which was
-    # crafted in CookHeaders.py to ensure prefix was stripped from the subject
-    # came from mailing list user.
+    # messages? TK: We use stripped_subject (prefix stripped) which was crafted
+    # in the subject-prefix handler to ensure prefix was stripped from the
+    # subject came from mailing list user.
     stripped_subject = msgdata.get('stripped_subject',
                                    msgdata.get('original_subject'))
     if not mlist.nntp_prefix_subject_too and stripped_subject is not None: