Add initial support for xml:lang for streams and stanza plugins.

Remaining items are suitable default actions for language supporting
interfaces.

10 files changed, 243 insertions, 89 deletions

diff --git a/sleekxmpp/basexmpp.py b/sleekxmpp/basexmpp.py
index 43ea6063..4f48f809 100644
--- a/sleekxmpp/basexmpp.py
+++ b/sleekxmpp/basexmpp.py
@@ -31,6 +31,7 @@ from sleekxmpp.xmlstream import XMLStream, JID
 from sleekxmpp.xmlstream import ET, register_stanza_plugin
 from sleekxmpp.xmlstream.matcher import MatchXPath
 from sleekxmpp.xmlstream.handler import Callback
+from sleekxmpp.xmlstream.stanzabase import XML_NS
 
 from sleekxmpp.features import *
 from sleekxmpp.plugins import PluginManager, register_plugin, load_plugin
@@ -180,6 +181,8 @@ class BaseXMPP(XMLStream):
         :param xml: The incoming stream's root element.
         """
         self.stream_id = xml.get('id', '')
+        self.stream_version = xml.get('version', '')
+        self.peer_default_lang = xml.get('{%s}lang' % XML_NS, None)
 
     def process(self, *args, **kwargs):
         """Initialize plugins and begin processing the XML stream.
@@ -272,7 +275,9 @@ class BaseXMPP(XMLStream):
 
     def Message(self, *args, **kwargs):
         """Create a Message stanza associated with this stream."""
-        return Message(self, *args, **kwargs)
+        msg = Message(self, *args, **kwargs)
+        msg['lang'] = self.default_lang
+        return msg
 
     def Iq(self, *args, **kwargs):
         """Create an Iq stanza associated with this stream."""
@@ -280,7 +285,9 @@ class BaseXMPP(XMLStream):
 
     def Presence(self, *args, **kwargs):
         """Create a Presence stanza associated with this stream."""
-        return Presence(self, *args, **kwargs)
+        pres = Presence(self, *args, **kwargs)
+        pres['lang'] = self.default_lang
+        return pres
 
     def make_iq(self, id=0, ifrom=None, ito=None, itype=None, iquery=None):
         """Create a new Iq stanza with a given Id and from JID.
diff --git a/sleekxmpp/clientxmpp.py b/sleekxmpp/clientxmpp.py
index 94ced031..8a941867 100644
--- a/sleekxmpp/clientxmpp.py
+++ b/sleekxmpp/clientxmpp.py
@@ -60,8 +60,8 @@ class ClientXMPP(BaseXMPP):
     :param escape_quotes: **Deprecated.**
     """
 
-    def __init__(self, jid, password, ssl=False, plugin_config={},
-                 plugin_whitelist=[], escape_quotes=True, sasl_mech=None):
+    def __init__(self, jid, password, plugin_config={}, plugin_whitelist=[], 
+                 escape_quotes=True, sasl_mech=None, lang='en'):
         BaseXMPP.__init__(self, jid, 'jabber:client')
 
         self.set_jid(jid)
@@ -69,15 +69,18 @@ class ClientXMPP(BaseXMPP):
         self.plugin_config = plugin_config
         self.plugin_whitelist = plugin_whitelist
         self.default_port = 5222
+        self.default_lang = lang
 
         self.credentials = {}
 
         self.password = password
 
-        self.stream_header = "<stream:stream to='%s' %s %s version='1.0'>" % (
+        self.stream_header = "<stream:stream to='%s' %s %s %s %s>" % (
                 self.boundjid.host,
                 "xmlns:stream='%s'" % self.stream_ns,
-                "xmlns='%s'" % self.default_ns)
+                "xmlns='%s'" % self.default_ns,
+                "xml:lang='%s'" % self.default_lang,
+                "version='1.0'")
         self.stream_footer = "</stream:stream>"
 
         self.features = set()
diff --git a/sleekxmpp/plugins/xep_0033.py b/sleekxmpp/plugins/xep_0033.py
index feef5a13..9276b807 100644
--- a/sleekxmpp/plugins/xep_0033.py
+++ b/sleekxmpp/plugins/xep_0033.py
@@ -42,6 +42,8 @@ class Addresses(ElementBase):
         self.delAddresses(set_type)
         for addr in addresses:
             addr = dict(addr)
+            if 'lang' in addr:
+                del addr['lang']
             # Remap 'type' to 'atype' to match the add method
             if set_type is not None:
                 addr['type'] = set_type
diff --git a/sleekxmpp/plugins/xep_0092/version.py b/sleekxmpp/plugins/xep_0092/version.py
index c6223c10..5e84b2ff 100644
--- a/sleekxmpp/plugins/xep_0092/version.py
+++ b/sleekxmpp/plugins/xep_0092/version.py
@@ -79,5 +79,7 @@ class XEP_0092(BasePlugin):
         result = iq.send()
 
         if result and result['type'] != 'error':
-            return result['software_version'].values
+            values = result['software_version'].values
+            del values['lang']
+            return values
         return False
diff --git a/sleekxmpp/stanza/roster.py b/sleekxmpp/stanza/roster.py
index 253c2aea..3fae42cc 100644
--- a/sleekxmpp/stanza/roster.py
+++ b/sleekxmpp/stanza/roster.py
@@ -102,6 +102,7 @@ class Roster(ElementBase):
                 # Remove extra JID reference to keep everything
                 # backward compatible
                 del items[item['jid']]['jid'] 
+                del items[item['jid']]['lang']
         return items
 
     def del_items(self):
diff --git a/sleekxmpp/test/sleektest.py b/sleekxmpp/test/sleektest.py
index ba79dce8..92a7688a 100644
--- a/sleekxmpp/test/sleektest.py
+++ b/sleekxmpp/test/sleektest.py
@@ -333,6 +333,9 @@ class SleekTest(unittest.TestCase):
         # Remove unique ID prefix to make it easier to test
         self.xmpp._id_prefix = ''
         self.xmpp._disconnect_wait_for_threads = False
+        self.xmpp.default_lang = None
+        self.xmpp.peer_default_lang = None
+
 
         # We will use this to wait for the session_start event
         # for live connections.
@@ -386,6 +389,7 @@ class SleekTest(unittest.TestCase):
                           sid='',
                           stream_ns="http://etherx.jabber.org/streams",
                           default_ns="jabber:client",
+                          default_lang="en",
                           version="1.0",
                           xml_header=True):
         """
@@ -413,6 +417,8 @@ class SleekTest(unittest.TestCase):
             parts.append('from="%s"' % sfrom)
         if sid:
             parts.append('id="%s"' % sid)
+        if default_lang:
+            parts.append('xml:lang="%s"' % default_lang)
         parts.append('version="%s"' % version)
         parts.append('xmlns:stream="%s"' % stream_ns)
         parts.append('xmlns="%s"' % default_ns)
@@ -564,6 +570,7 @@ class SleekTest(unittest.TestCase):
                           sid='',
                           stream_ns="http://etherx.jabber.org/streams",
                           default_ns="jabber:client",
+                          default_lang="en",
                           version="1.0",
                           xml_header=False,
                           timeout=1):
@@ -585,6 +592,7 @@ class SleekTest(unittest.TestCase):
         header = self.make_header(sto, sfrom, sid,
                                   stream_ns=stream_ns,
                                   default_ns=default_ns,
+                                  default_lang=default_lang,
                                   version=version,
                                   xml_header=xml_header)
         sent_header = self.xmpp.socket.next_sent(timeout)
diff --git a/sleekxmpp/xmlstream/stanzabase.py b/sleekxmpp/xmlstream/stanzabase.py
index 5d572437..f06573bf 100644
--- a/sleekxmpp/xmlstream/stanzabase.py
+++ b/sleekxmpp/xmlstream/stanzabase.py
@@ -12,6 +12,8 @@
     :license: MIT, see LICENSE for more details
 """
 
+from __future__ import with_statement, unicode_literals
+
 import copy
 import logging
 import weakref
@@ -29,6 +31,9 @@ log = logging.getLogger(__name__)
 XML_TYPE = type(ET.Element('xml'))
 
 
+XML_NS = 'http://www.w3.org/XML/1998/namespace'
+
+
 def register_stanza_plugin(stanza, plugin, iterable=False, overrides=False):
     """
     Associate a stanza object as a plugin for another stanza.
@@ -101,20 +106,26 @@ def multifactory(stanza, plugin_attrib):
         def setup(self, xml=None):
             self.xml = ET.Element('')
 
-    def get_multi(self):
+    def get_multi(self, lang=None):
         parent = self.parent()
-        res = filter(lambda sub: isinstance(sub, self._multistanza), parent)
+        if lang is None:
+            res = filter(lambda sub: isinstance(sub, self._multistanza), parent)
+        else:
+            res = filter(lambda sub: isinstance(sub, self._multistanza) and sub['lang'] == lang, parent)
         return list(res)
 
-    def set_multi(self, val):
+    def set_multi(self, val, lang=None):
         parent = self.parent()
         del parent[self.plugin_attrib]
         for sub in val:
             parent.append(sub)
 
-    def del_multi(self):
+    def del_multi(self, lang=None):
         parent = self.parent()
-        res = filter(lambda sub: isinstance(sub, self._multistanza), parent)
+        if lang is None:
+            res = filter(lambda sub: isinstance(sub, self._multistanza), parent)
+        else:
+            res = filter(lambda sub: isinstance(sub, self._multistanza) and sub['lang'] == lang, parent)
         for stanza in list(res):
             parent.iterables.remove(stanza)
             parent.xml.remove(stanza.xml)
@@ -122,7 +133,8 @@ def multifactory(stanza, plugin_attrib):
     Multi.is_extension = True
     Multi.plugin_attrib = plugin_attrib
     Multi._multistanza = stanza
-    Multi.interfaces = (plugin_attrib,)
+    Multi.interfaces = set([plugin_attrib])
+    Multi.lang_interfaces = set([plugin_attrib])
     setattr(Multi, "get_%s" % plugin_attrib, get_multi)
     setattr(Multi, "set_%s" % plugin_attrib, set_multi)
     setattr(Multi, "del_%s" % plugin_attrib, del_multi)
@@ -289,14 +301,17 @@ class ElementBase(object):
     #: subelements of the underlying XML object. Using this set, the text
     #: of these subelements may be set, retrieved, or removed without
     #: needing to define custom methods.
-    sub_interfaces = tuple()
+    sub_interfaces = set()
 
     #: A subset of :attr:`interfaces` which maps the presence of
     #: subelements to boolean values. Using this set allows for quickly
     #: checking for the existence of empty subelements like ``<required />``.
     #:
     #: .. versionadded:: 1.1
-    bool_interfaces = tuple()
+    bool_interfaces = set()
+
+    #: .. versionadded:: 1.1.2
+    lang_interfaces = set()
 
     #: In some cases you may wish to override the behaviour of one of the
     #: parent stanza's interfaces. The ``overrides`` list specifies the
@@ -363,7 +378,7 @@ class ElementBase(object):
     subitem = set()
 
     #: The default XML namespace: ``http://www.w3.org/XML/1998/namespace``.
-    xml_ns = 'http://www.w3.org/XML/1998/namespace'
+    xml_ns = XML_NS
 
     def __init__(self, xml=None, parent=None):
         self._index = 0
@@ -375,6 +390,7 @@ class ElementBase(object):
         #: An ordered dictionary of plugin stanzas, mapped by their
         #: :attr:`plugin_attrib` value.
         self.plugins = OrderedDict()
+        self.loaded_plugins = set()
 
         #: A list of child stanzas whose class is included in
         #: :attr:`plugin_iterables`.
@@ -385,6 +401,12 @@ class ElementBase(object):
         #: ``'{namespace}elementname'``.
         self.tag = self.tag_name()
 
+        if 'lang' not in self.interfaces:
+            if isinstance(self.interfaces, tuple):
+                self.interfaces += ('lang',)
+            else:
+                self.interfaces.add('lang')
+
         #: A :class:`weakref.weakref` to the parent stanza, if there is one.
         #: If not, then :attr:`parent` is ``None``.
         self.parent = None
@@ -406,10 +428,9 @@ class ElementBase(object):
         for child in self.xml.getchildren():
             if child.tag in self.plugin_tag_map:
                 plugin_class = self.plugin_tag_map[child.tag]
-                plugin = plugin_class(child, self)
-                self.plugins[plugin.plugin_attrib] = plugin
-                if plugin_class in self.plugin_iterables:
-                    self.iterables.append(plugin)
+                self.init_plugin(plugin_class.plugin_attrib,
+                                 existing_xml=child,
+                                 reuse=False)
 
     def setup(self, xml=None):
         """Initialize the stanza's XML contents.
@@ -443,7 +464,7 @@ class ElementBase(object):
             # We did not generate XML
             return False
 
-    def enable(self, attrib):
+    def enable(self, attrib, lang=None):
         """Enable and initialize a stanza plugin.
 
         Alias for :meth:`init_plugin`.
@@ -451,24 +472,60 @@ class ElementBase(object):
         :param string attrib: The :attr:`plugin_attrib` value of the
                               plugin to enable.
         """
-        return self.init_plugin(attrib)
+        return self.init_plugin(attrib, lang)
+
+    def _get_plugin(self, name, lang=None):
+        if lang is None:
+            lang = self.get_lang()
+        plugin_class = self.plugin_attrib_map[name]
+        if plugin_class.is_extension:
+            if (name, None) in self.plugins:
+                return self.plugins[(name, None)]
+            else:
+                return self.init_plugin(name, lang)
+        else:
+            if (name, lang) in self.plugins:
+                return self.plugins[(name, lang)]
+            else:
+                return self.init_plugin(name, lang)
 
-    def init_plugin(self, attrib):
+    def init_plugin(self, attrib, lang=None, existing_xml=None, reuse=True):
         """Enable and initialize a stanza plugin.
 
         :param string attrib: The :attr:`plugin_attrib` value of the
                               plugin to enable.
         """
-        if attrib not in self.plugins:
-            plugin_class = self.plugin_attrib_map[attrib]
+        if lang is None:
+            lang = self.get_lang()
+
+        plugin_class = self.plugin_attrib_map[attrib]
+
+        if plugin_class.is_extension and (attrib, None) in self.plugins:
+            return self.plugins[(attrib, None)]
+        if reuse and (attrib, lang) in self.plugins:
+            return self.plugins[(attrib, lang)]
+
+        if existing_xml is None:
             existing_xml = self.xml.find(plugin_class.tag_name())
-            plugin = plugin_class(parent=self, xml=existing_xml)
-            self.plugins[attrib] = plugin
-            if plugin_class in self.plugin_iterables:
-                self.iterables.append(plugin)
-                if plugin_class.plugin_multi_attrib:
-                    self.init_plugin(plugin_class.plugin_multi_attrib)
-        return self
+        if existing_xml is not None and existing_xml.attrib.get('{%s}lang' % XML_NS, '') != lang:
+            existing_xml = None
+
+        plugin = plugin_class(parent=self, xml=existing_xml)
+
+        if plugin.is_extension:
+            self.plugins[(attrib, None)] = plugin
+        else:
+            plugin['lang'] = lang
+            self.plugins[(attrib, lang)] = plugin
+
+        if plugin_class in self.plugin_iterables:
+            self.iterables.append(plugin)
+            if plugin_class.plugin_multi_attrib:
+                self.init_plugin(plugin_class.plugin_multi_attrib)
+
+        self.loaded_plugins.add(attrib)
+
+        return plugin
 
     def _get_stanza_values(self):
         """Return A JSON/dictionary version of the XML content
@@ -493,7 +550,11 @@ class ElementBase(object):
         for interface in self.interfaces:
             values[interface] = self[interface]
         for plugin, stanza in self.plugins.items():
-            values[plugin] = stanza.values
+            lang = stanza['lang']
+            if lang:
+                values['%s|%s' % (plugin, lang)] = stanza.values
+            else:
+                values[plugin[0]] = stanza.values
         if self.iterables:
             iterables = []
             for stanza in self.iterables:
@@ -517,6 +578,11 @@ class ElementBase(object):
                                     p in self.plugin_iterables]
 
         for interface, value in values.items():
+            full_interface = interface
+            interface_lang = ('%s|' % interface).split('|')
+            interface = interface_lang[0]
+            lang = interface_lang[1] or self.get_lang()
+
             if interface == 'substanzas':
                 # Remove existing substanzas
                 for stanza in self.iterables:
@@ -538,9 +604,8 @@ class ElementBase(object):
                 self[interface] = value
             elif interface in self.plugin_attrib_map:
                 if interface not in iterable_interfaces:
-                    if interface not in self.plugins:
-                        self.init_plugin(interface)
-                    self.plugins[interface].values = value
+                    plugin = self._get_plugin(interface, lang)
+                    plugin.values = value
         return self
 
     def __getitem__(self, attrib):
@@ -572,6 +637,15 @@ class ElementBase(object):
 
         :param string attrib: The name of the requested stanza interface.
         """
+        full_attrib = attrib
+        attrib_lang = ('%s|' % attrib).split('|')
+        attrib = attrib_lang[0]
+        lang = attrib_lang[1] or ''
+
+        kwargs = {}
+        if lang and attrib in self.lang_interfaces:
+            kwargs['lang'] = lang
+
         if attrib == 'substanzas':
             return self.iterables
         elif attrib in self.interfaces:
@@ -579,18 +653,17 @@ class ElementBase(object):
             get_method2 = "get%s" % attrib.title()
 
             if self.plugin_overrides:
-                plugin = self.plugin_overrides.get(get_method, None)
-                if plugin:
-                    if plugin not in self.plugins:
-                        self.init_plugin(plugin)
-                    handler = getattr(self.plugins[plugin], get_method, None)
+                name = self.plugin_overrides.get(get_method, None)
+                if name:
+                    plugin = self._get_plugin(name, lang)
+                    handler = getattr(plugin, get_method, None)
                     if handler:
-                        return handler()
+                        return handler(**kwargs)
 
             if hasattr(self, get_method):
-                return getattr(self, get_method)()
+                return getattr(self, get_method)(**kwargs)
             elif hasattr(self, get_method2):
-                return getattr(self, get_method2)()
+                return getattr(self, get_method2)(**kwargs)
             else:
                 if attrib in self.sub_interfaces:
                     return self._get_sub_text(attrib)
@@ -600,11 +673,10 @@ class ElementBase(object):
                 else:
                     return self._get_attr(attrib)
         elif attrib in self.plugin_attrib_map:
-            if attrib not in self.plugins:
-                self.init_plugin(attrib)
-            if self.plugins[attrib].is_extension:
-                return self.plugins[attrib][attrib]
-            return self.plugins[attrib]
+            plugin = self._get_plugin(attrib, lang)
+            if plugin.is_extension:
+                return plugin[full_attrib]
+            return plugin
         else:
             return ''
 
@@ -640,25 +712,32 @@ class ElementBase(object):
         :param string attrib: The name of the stanza interface to modify.
         :param value: The new value of the stanza interface.
         """
+        full_attrib = attrib
+        attrib_lang = ('%s|' % attrib).split('|')
+        attrib = attrib_lang[0]
+        lang = attrib_lang[1] or ''
+
+        kwargs = {}
+        if lang and attrib in self.lang_interfaces:
+            kwargs['lang'] = lang
+
         if attrib in self.interfaces:
             if value is not None:
                 set_method = "set_%s" % attrib.lower()
                 set_method2 = "set%s" % attrib.title()
 
                 if self.plugin_overrides:
-                    plugin = self.plugin_overrides.get(set_method, None)
-                    if plugin:
-                        if plugin not in self.plugins:
-                            self.init_plugin(plugin)
-                        handler = getattr(self.plugins[plugin],
-                                          set_method, None)
+                    name = self.plugin_overrides.get(set_method, None)
+                    if name:
+                        plugin = self._get_plugin(name, lang)
+                        handler = getattr(plugin, set_method, None)
                         if handler:
-                            return handler(value)
+                            return handler(value, **kwargs)
 
                 if hasattr(self, set_method):
-                    getattr(self, set_method)(value,)
+                    getattr(self, set_method)(value, **kwargs)
                 elif hasattr(self, set_method2):
-                    getattr(self, set_method2)(value,)
+                    getattr(self, set_method2)(value, **kwargs)
                 else:
                     if attrib in self.sub_interfaces:
                         return self._set_sub_text(attrib, text=value)
@@ -672,9 +751,8 @@ class ElementBase(object):
             else:
                 self.__delitem__(attrib)
         elif attrib in self.plugin_attrib_map:
-            if attrib not in self.plugins:
-                self.init_plugin(attrib)
-            self.plugins[attrib][attrib] = value
+            plugin = self._get_plugin(attrib, lang)
+            plugin[full_attrib] = value
         return self
 
     def __delitem__(self, attrib):
@@ -709,23 +787,31 @@ class ElementBase(object):
 
         :param attrib: The name of the affected stanza interface.
         """
+        full_attrib = attrib
+        attrib_lang = ('%s|' % attrib).split('|')
+        attrib = attrib_lang[0]
+        lang = attrib_lang[1] or ''
+
+        kwargs = {}
+        if lang and attrib in self.lang_interfaces:
+            kwargs['lang'] = lang
+
         if attrib in self.interfaces:
             del_method = "del_%s" % attrib.lower()
             del_method2 = "del%s" % attrib.title()
 
             if self.plugin_overrides:
-                plugin = self.plugin_overrides.get(del_method, None)
-                if plugin:
-                    if plugin not in self.plugins:
-                        self.init_plugin(plugin)
-                    handler = getattr(self.plugins[plugin], del_method, None)
+                name = self.plugin_overrides.get(del_method, None)
+                if name:
+                    plugin = self._get_plugin(attrib, lang)
+                    handler = getattr(plugin, del_method, None)
                     if handler:
-                        return handler()
+                        return handler(**kwargs)
 
             if hasattr(self, del_method):
-                getattr(self, del_method)()
+                getattr(self, del_method)(**kwargs)
             elif hasattr(self, del_method2):
-                getattr(self, del_method2)()
+                getattr(self, del_method2)(**kwargs)
             else:
                 if attrib in self.sub_interfaces:
                     return self._del_sub(attrib)
@@ -734,15 +820,17 @@ class ElementBase(object):
                 else:
                     self._del_attr(attrib)
         elif attrib in self.plugin_attrib_map:
-            if attrib in self.plugins:
-                xml = self.plugins[attrib].xml
-                if self.plugins[attrib].is_extension:
-                    del self.plugins[attrib][attrib]
-                del self.plugins[attrib]
-                try:
-                    self.xml.remove(xml)
-                except:
-                    pass
+            plugin = self._get_plugin(attrib, lang)
+            if plugin.is_extension:
+                del plugin[full_attrib]
+                del self.plugins[(attrib, None)]
+            else:
+                del self.plugins[(attrib, lang)]
+            self.loaded_plugins.remove(attrib)
+            try:
+                self.xml.remove(plugin.xml)
+            except:
+                pass
         return self
 
     def _set_attr(self, name, value):
@@ -903,7 +991,7 @@ class ElementBase(object):
         attributes = components[1:]
 
         if tag not in (self.name, "{%s}%s" % (self.namespace, self.name)) and \
-            tag not in self.plugins and tag not in self.plugin_attrib:
+            tag not in self.loaded_plugins and tag not in self.plugin_attrib:
             # The requested tag is not in this stanza, so no match.
             return False
 
@@ -932,10 +1020,11 @@ class ElementBase(object):
         if not matched_substanzas and len(xpath) > 1:
             # Convert {namespace}tag@attribs to just tag
             next_tag = xpath[1].split('@')[0].split('}')[-1]
-            if next_tag in self.plugins:
-                return self.plugins[next_tag].match(xpath[1:])
-            else:
-                return False
+            langs = [name[1] for name in self.plugins if name[0] == next_tag]
+            for lang in langs:
+                if self._get_plugin(next_tag, lang).match(xpath[1:]):
+                    return True
+            return False
 
         # Everything matched.
         return True
@@ -995,7 +1084,7 @@ class ElementBase(object):
         """
         out = []
         out += [x for x in self.interfaces]
-        out += [x for x in self.plugins]
+        out += [x for x in self.loaded_plugins]
         if self.iterables:
             out.append('substanzas')
         return out
@@ -1075,6 +1164,23 @@ class ElementBase(object):
         """
         return "{%s}%s" % (cls.namespace, cls.name)
 
+    def get_lang(self):
+        result = self.xml.attrib.get('{%s}lang' % XML_NS, '')
+        if not result and self.parent and self.parent():
+            return self.parent()['lang']
+        return result
+
+    def set_lang(self, lang):
+        self.del_lang()
+        attr = '{%s}lang' % XML_NS
+        if lang:
+            self.xml.attrib[attr] = lang
+
+    def del_lang(self):
+        attr = '{%s}lang' % XML_NS
+        if attr in self.xml.attrib:
+            del self.xml.attrib[attr]
+
     @property
     def attrib(self):
         """Return the stanza object itself.
diff --git a/sleekxmpp/xmlstream/tostring.py b/sleekxmpp/xmlstream/tostring.py
index 8e729f79..379ea09a 100644
--- a/sleekxmpp/xmlstream/tostring.py
+++ b/sleekxmpp/xmlstream/tostring.py
@@ -13,14 +13,19 @@
     :license: MIT, see LICENSE for more details
 """
 
+from __future__ import unicode_literals
+
 import sys
 
 if sys.version_info < (3, 0):
     import types
 
 
+XML_NS = 'http://www.w3.org/XML/1998/namespace'
+
+
 def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
-             outbuffer='', top_level=False):
+             outbuffer='', top_level=False, open_only=False):
     """Serialize an XML object to a Unicode string.
 
     If namespaces are provided using ``xmlns`` or ``stanza_ns``, then
@@ -88,6 +93,13 @@ def tostring(xml=None, xmlns='', stanza_ns='', stream=None,
                     output.append(' %s:%s="%s"' % (mapped_ns,
                                                    attrib,
                                                    value))
+            elif attrib_ns == XML_NS:
+                output.append(' xml:%s="%s"' % (attrib, value))
+
+    if open_only:
+        # Only output the opening tag, regardless of content.
+        output.append(">")
+        return ''.join(output)
 
     if len(xml) or xml.text:
         # If there are additional child elements to serialize.
diff --git a/sleekxmpp/xmlstream/xmlstream.py b/sleekxmpp/xmlstream/xmlstream.py
index 40ae38c9..14c13e72 100644
--- a/sleekxmpp/xmlstream/xmlstream.py
+++ b/sleekxmpp/xmlstream/xmlstream.py
@@ -223,6 +223,9 @@ class XMLStream(object):
         #: stream wrapper itself.
         self.default_ns = ''
 
+        self.default_lang = None
+        self.peer_default_lang = None
+
         #: The namespace of the enveloping stream element.
         self.stream_ns = ''
 
@@ -1431,6 +1434,10 @@ class XMLStream(object):
                 if depth == 0:
                     # We have received the start of the root element.
                     root = xml
+                    log.debug('RECV: %s', tostring(root, xmlns=self.default_ns,
+                                                         stream=self, 
+                                                         top_level=True, 
+                                                         open_only=True))
                     # Perform any stream initialization actions, such
                     # as handshakes.
                     self.stream_end_event.clear()
@@ -1478,6 +1485,8 @@ class XMLStream(object):
                 stanza_type = stanza_class
                 break
         stanza = stanza_type(self, xml)
+        if stanza['lang'] is None and self.peer_default_lang:
+            stanza['lang'] = self.peer_default_lang
         return stanza
 
     def __spawn_event(self, xml):
diff --git a/tests/test_stanza_element.py b/tests/test_stanza_element.py
index 09093003..1b47e733 100644
--- a/tests/test_stanza_element.py
+++ b/tests/test_stanza_element.py
@@ -64,14 +64,18 @@ class TestElementBase(SleekTest):
         stanza.append(substanza)
 
         values = stanza.getStanzaValues()
-        expected = {'bar': 'a',
+        expected = {'lang': '',
+                    'bar': 'a',
                     'baz': '',
-                    'foo2': {'bar': '',
+                    'foo2': {'lang': '',
+                             'bar': '',
                              'baz': 'b'},
                     'substanzas': [{'__childtag__': '{foo}foo2',
+                                    'lang': '',
                                     'bar': '',
                                     'baz': 'b'},
                                    {'__childtag__': '{foo}subfoo',
+                                    'lang': '',
                                     'bar': 'c',
                                     'baz': ''}]}
         self.failUnless(values == expected,
@@ -555,12 +559,12 @@ class TestElementBase(SleekTest):
 
         stanza = TestStanza()
 
-        self.failUnless(set(stanza.keys()) == set(('bar', 'baz')),
+        self.failUnless(set(stanza.keys()) == set(('lang', 'bar', 'baz')),
             "Returned set of interface keys does not match expected.")
 
         stanza.enable('qux')
 
-        self.failUnless(set(stanza.keys()) == set(('bar', 'baz', 'qux')),
+        self.failUnless(set(stanza.keys()) == set(('lang', 'bar', 'baz', 'qux')),
             "Incorrect set of interface and plugin keys.")
 
     def testGet(self):