Update tostring to inject xmlns definitions when needed.

1 files changed, 22 insertions, 7 deletions

diff --git a/sleekxmpp/xmlstream/tostring.py b/sleekxmpp/xmlstream/tostring.py
index 08d7ad02..f4157f7a 100644
--- a/sleekxmpp/xmlstream/tostring.py
+++ b/sleekxmpp/xmlstream/tostring.py
@@ -24,8 +24,8 @@ if sys.version_info < (3, 0):
 XML_NS = 'http://www.w3.org/XML/1998/namespace'
 
 
-def tostring(xml=None, xmlns='', stream=None,
-             outbuffer='', top_level=False, open_only=False):
+def tostring(xml=None, xmlns='', stream=None, outbuffer='',
+             top_level=False, open_only=False, namespaces=None):
     """Serialize an XML object to a Unicode string.
 
     If an outer xmlns is provided using ``xmlns``, then the current element's
@@ -41,7 +41,8 @@ def tostring(xml=None, xmlns='', stream=None,
                              during recursive calls.
     :param bool top_level: Indicates that the element is the outermost
                            element.
-
+    :param set namespaces: Track which namespaces are in active use so
+                           that new ones can be declared when needed.
 
     :type xml: :py:class:`~xml.etree.ElementTree.Element`
     :type stream: :class:`~sleekxmpp.xmlstream.xmlstream.XMLStream`
@@ -63,6 +64,7 @@ def tostring(xml=None, xmlns='', stream=None,
     default_ns = ''
     stream_ns = ''
     use_cdata = False
+
     if stream:
         default_ns = stream.default_ns
         stream_ns = stream.stream_ns
@@ -82,6 +84,7 @@ def tostring(xml=None, xmlns='', stream=None,
     output.append(namespace)
 
     # Output escaped attribute values.
+    new_namespaces = set()
     for attrib, value in xml.attrib.items():
         value = escape(value, use_cdata)
         if '}' not in attrib:
@@ -92,9 +95,15 @@ def tostring(xml=None, xmlns='', stream=None,
             if stream and attrib_ns in stream.namespace_map:
                 mapped_ns = stream.namespace_map[attrib_ns]
                 if mapped_ns:
-                    output.append(' %s:%s="%s"' % (mapped_ns,
-                                                   attrib,
-                                                   value))
+                    if namespaces is None:
+                        namespaces = set()
+                    if attrib_ns not in namespaces:
+                        namespaces.add(attrib_ns)
+                        new_namespaces.add(attrib_ns)
+                        output.append(' xmlns:%s="%s"' % (
+                            mapped_ns, attrib_ns))
+                    output.append(' %s:%s="%s"' % (
+                        mapped_ns, attrib, value))
             elif attrib_ns == XML_NS:
                 output.append(' xml:%s="%s"' % (attrib, value))
 
@@ -110,7 +119,8 @@ def tostring(xml=None, xmlns='', stream=None,
             output.append(escape(xml.text, use_cdata))
         if len(xml):
             for child in xml:
-                output.append(tostring(child, tag_xmlns, stream))
+                output.append(tostring(child, tag_xmlns, stream,
+                    namespaces=namespaces))
         output.append("</%s>" % tag_name)
     elif xml.text:
         # If we only have text content.
@@ -121,6 +131,11 @@ def tostring(xml=None, xmlns='', stream=None,
     if xml.tail:
         # If there is additional text after the element.
         output.append(escape(xml.tail, use_cdata))
+    for ns in new_namespaces:
+        # Remove namespaces introduced in this context. This is necessary
+        # because the namespaces object continues to be shared with other
+        # contexts.
+        namespaces.remove(ns)
     return ''.join(output)