gh-128302: fix apparent bug in xml.dom.xmlbuilder.DOMBuilder.parse()

[tungol]

This looks like a bug. The Options class has no systemId attribute, but the input parameter, which seems to be an instance of DOMInputSource, does.

I don't really know how this is meant to be used, but given this code:

from xml.dom.xmlbuilder import DOMBuilder, DOMInputSource

db = DOMBuilder()
source = DOMInputSource()
source.systemId = "http://www.w3.org/2000/svg"
print(db.parse(source))

As-is this raises an error:

  File "test.py", line 6, in <module>
    print(db.parse(source))
          ~~~~~~~~^^^^^^^^
  File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/xml/dom/xmlbuilder.py", line 192, in parse
    if fp is None and options.systemId:
                      ^^^^^^^^^^^^^^^^
AttributeError: 'Options' object has no attribute 'systemId'

With this change:

<xml.dom.minidom.Document object at 0x105438f50>

I'd consider adding a test, but there's no tests right now for any of this.

• Issue: Bug in xml.dom.xmlbuilder.DOMBuilder.parse() #128302

[picnixz]

Considering the fact that we use input.systemId just after, I don't know if the options class is meant to indicate "hey, you can use systemId", I think we need an issue as well and a NEWS entry.

[tungol]

I'll put together a more thorough analysis.

[tungol]

Please see issue #128302 for a full write-up and analysis of what's going on here.