XMLGenerator.startElementNS dies on EMPTY_NAMESPACE attribut

[zenzen]

BPO	847665
Nosy	@loewis, @akuchling
Files	startElementNS.py: Replacement startElementNS and endElementNS

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2007-02-12.12:23:30.000>
created_at = <Date 2003-11-23.15:21:36.000>
labels = ['expert-XML']
title = 'XMLGenerator.startElementNS dies on EMPTY_NAMESPACE attribut'
updated_at = <Date 2007-02-12.12:23:30.000>
user = 'https://bugs.python.org/zenzen'

bugs.python.org fields:

activity = <Date 2007-02-12.12:23:30.000>
actor = 'loewis'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['XML']
creation = <Date 2003-11-23.15:21:36.000>
creator = 'zenzen'
dependencies = []
files = ['1109']
hgrepos = []
issue_num = 847665
keywords = []
message_count = 7.0
messages = ['19095', '19096', '19097', '19098', '19099', '19100', '19101']
nosy_count = 4.0
nosy_names = ['loewis', 'akuchling', 'zenzen', 'ngrig']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue847665'
versions = ['Python 2.3']

[zenzen]

from xml.sax.saxutils import XMLGenerator

g = XMLGenerator(encoding='utf8')
STREAM_NAMESPACE = 'http://etherx.jabber.org/streams'
CLIENT_NAMESPACE = 'jabber:client'
g.startDocument()
g.startPrefixMapping('stream', STREAM_NAMESPACE)
g.startPrefixMapping('client', CLIENT_NAMESPACE)
g.startElementNS( 
    (STREAM_NAMESPACE, 'stream'), 'stream',
    {(None,'xmlns'): CLIENT_NAMESPACE}
    )

Dies with:
Traceback (most recent call last):
  File "tst.py", line 11, in ?
    g.startElementNS( 
  File "/System/Library/Frameworks/Python.framework/
Versions/2.3/lib/python2.3/xml/sax/saxutils.py", line 124, in 
startElementNS
    name = self._current_context[name[0]] + ":" + name[1]
KeyError: 'x'

Changing the end of XMLGenerator.startElementNS to the
following makes it work the way I expect:

        for (name, value) in attrs.items():
            if name[0] is None:
                name = name[1]
            else:
                name = self._current_context[name[0]] + ":" + 
name[1]
            self._out.write(' %s=%s' % (name, 
quoteattr(value)))
        self._out.write('>')

[zenzen]

Logged In: YES
user_id=46639

This method also appears to have trouble emmitting tags without a
namespace prefix:

import xml.sax
import xml.sax.handler
import xml.sax.saxutils
x = '''<?xml version="1.0"?><mechanisms xmlns='urn:ietf:
params:xml:ns:xmpp-sasl'
>'''
parser = xml.sax.make_parser()
parser.setFeature(xml.sax.handler.feature_namespaces, True)
parser.setContentHandler(xml.sax.saxutils.XMLGenerator())
parser.feed(x)

dies with:
Traceback (most recent call last):
  File "tst.py", line 30, in ?
    parser.feed(x)
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/expatreader.py", line 207, in feed
    self._parser.Parse(data, isFinal)
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/expatreader.py", line 337, in 
start_element_ns
    AttributesNSImpl(newattrs, qnames))
  File "/System/Library/Frameworks/Python.framework/Versions/
2.3/lib/python2.3/xml/sax/saxutils.py", line 116, in startElementNS
    name = self._current_context[name[0]] + ":" + name[1]
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

I've attached my current replacement startElementNS method
which appears to fix both this and the previous issue.

[akuchling]

Logged In: YES
user_id=11375

I don't understand your second example; it uses saxutils to
parse a file. What's it got to do with XMLGenerator?

[akuchling]

Logged In: YES
user_id=11375

Never mind my previous comment; I just noticed the
setContentHandler call.

[akuchling]

Logged In: YES
user_id=11375

Please provide your changes in the form of a patch.

[ngrig]

Logged In: YES
user_id=195108

This issue lasts for 2.5 years already. I feel like it is
somewhat stalled.

The processing of XML namespaces in saxutils.XMLGenerator is
so blatantly broken that I wonder if it ever has been tested
at all. I wrote down a simple smoke test for it:

import sys
from xml import sax
from xml.sax.saxutils import XMLGenerator
from StringIO import StringIO

tests = [
("No namespace, no attributes",     "<a/>"),
("No namespace, with attributes",   "<a b='c'/>"),
("Empty prefix, no attributes",     "<a xmlns='qux'/>"),
("Empty prefix, unprefixed attributes", "<a xmlns='qux'
b='c'/>"),
("Prefixed, no attributes",         "<my:a xmlns:my='qux'/>"),
("Prefixed, unprefixed attributes", "<my:a xmlns:my='qux'
b='c'/>"),               
("Prefixed, prefixed attributes",   "<my:a xmlns:my='qux'
my:b='c'/>"),
]
          
for (caption, testdoc) in tests:
    try:
        parser = sax.make_parser()
        parser.setFeature(sax.handler.feature_namespaces, 1)
        parser.setContentHandler(XMLGenerator(StringIO()))
        parser.parse(StringIO(testdoc))
        print caption, "- OK"
    except StandardError, e:
        print caption, "- FAILED:", e.__class__.__name__

With the current version of saxutils (as of Python 2.4.1), I
get 4 failures out of 7. Stuart Bishop's patch fixes the
issue; could someone commit it please?

[loewis]

This is now fixed in r53754 and r53755.