Add decodefoldernames option to decode IMAP folder names using UTF-7.

Signed-off-by: Tommie Gannert <tommie@gannert.se>

offlineimap.conf

@@ -762,6 +762,20 @@ remoteuser = username
 #reference = Mail
 
 
+# This option stands in the [Repository RemoteExample] section.
+#
+# IMAP defines an encoding for non-ASCII ("international") characters. Enable
+# this option if you want to decode them to the nowadays ubiquitous UTF-8.
+#
+# Note that the IMAP 4rev1 specification (RFC 3501) allows both UTF-8 and
+# modified UTF-7 folder names.
+#
+# This option is disabled by default to retain compatibility with older versions
+# of offlineimap.
+#
+#decodefoldernames = no
+
+
 # This option stands in the [Repository RemoteExample] section.
 #
 # In between synchronisations, OfflineIMAP can monitor mailboxes for new

offlineimap/folder/IMAP.py

@@ -258,6 +258,13 @@ class IMAPFolder(BaseFolder):
     def dropmessagelistcache(self):
         self.messagelist = {}
 
+    # Interface from BaseFolder
+    def getvisiblename(self):
+        vname = super(IMAPFolder, self).getvisiblename()
+        if self.repository.getdecodefoldernames():
+            return imaputil.decode_mailbox_name(vname)
+        return vname
+
     # Interface from BaseFolder
     def getmessagelist(self):
         return self.messagelist

offlineimap/imaputil.py

@@ -25,6 +25,9 @@ from offlineimap.ui import getglobalui
 # Message headers that use space as the separator (for label storage)
 SPACE_SEPARATED_LABEL_HEADERS = ('X-Label', 'Keywords')
 
+# Find the modified UTF-7 shifts of an international mailbox name.
+MUTF7_SHIFT_RE = re.compile(r'&[^-]*-|\+')
+
 
 def __debug(*args):
     msg = []
@@ -328,3 +331,28 @@ def labels_from_header(header_name, header_value):
 
     return labels
 
+
+def decode_mailbox_name(name):
+    """Decodes a modified UTF-7 mailbox name.
+
+    If the string cannot be decoded, it is returned unmodified.
+
+    See RFC 3501, sec. 5.1.3.
+
+    Arguments:
+    - name: string, possibly encoded with modified UTF-7
+
+    Returns: decoded UTF-8 string.
+    """
+    def demodify(m):
+        s = m.group()
+        if s == '+':
+            return '+-'
+        return '+' + s[1:-1].replace(',', '/') + '-'
+
+    ret = MUTF7_SHIFT_RE.sub(demodify, name)
+
+    try:
+        return ret.decode('utf-7').encode('utf-8')
+    except UnicodeEncodeError:
+        return name

offlineimap/repository/IMAP.py

@@ -261,6 +261,9 @@ class IMAPRepository(BaseRepository):
     def getreference(self):
         return self.getconf('reference', '')
 
+    def getdecodefoldernames(self):
+        return self.getconfboolean('decodefoldernames', 0)
+
     def getidlefolders(self):
         localeval = self.localeval
         return localeval.eval(self.getconf('idlefolders', '[]'))