ExpatParser raise exception during close action

[yabb85]

Hi,

I try to understand why ExpatParser raise exception during close action.
I create a xml parser with asyncio protocol to parse xmpp message.

class XMLProtocol(asyncio.Protocol):

during connection_made call I create parser and attach handler:

self._parser = make_parser()                            
self._handler = XMLHandler(self._transport, self._bunny)
self._parser.setContentHandler(self._handler)           

In data_received function I parse data on close document:

def data_received(self, data):
    try:
        data = data.replace(b"<?xml version='1.0' encoding='UTF-8'?>", b"").decode().strip()
        self._parser.feed(data)
        self._parser.close()
        self._parser.setContentHandler(self._handler)
        self._parser.reset()
    except UnicodeDecodeError:
        pass

But the close() call raise exception:

xml.sax._exceptions.SAXParseException: <unknown>:1:109: no element found

I check with pdb and the issue come from:

cpython/Lib/xml/sax/expatreader.py

Line 248 in cb18269

self.feed(b"", isFinal=True)

The following line not support empty data and isFinal at the same time:

cpython/Lib/xml/sax/expatreader.py

Line 211 in cb18269

self._parser.Parse(data, isFinal)

In my debugger I can see the following values for this line:

(Pdb) self._parser
<pyexpat.xmlparser object at 0x7f5041bfffa0>

(Pdb) self._parser.Parse
<built-in method Parse of pyexpat.xmlparser object at 0x7f5041bfffa0>

(Pdb) data
b''
(Pdb) isFinal
True

CPython versions tested on:
3.11.2

Operating systems tested on:
Linux (debian)

[serhiy-storchaka]

It raises exception because no element found. The XML document should contain one (and only one) root element (which can contain nested elements). Your data has none. Try to print all data that you feeds the parser.