searching for XML elements with position predicates does not work at all when namespaces are involved.

Bug report

Bug description:

Failure with namespaces:

Python 3.12.7 | packaged by conda-forge | (main, Oct  4 2024, 16:05:46) [GCC 13.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import xml.etree.ElementTree as ET
>>> ET.XML('<a xmlns="http://www.example.com/default-schema"><b/><b/></a>').find("./b[1]", {"": "http://www.example.com/default-schema"})
>>> ET.XML('<a xmlns="http://www.example.com/default-schema"><b/><b/></a>').find("./b[last()]", {"": "http://www.example.com/default-schema"})
Traceback (most recent call last):
  File "/home/lukas/miniforge3/envs/roads/lib/python3.12/xml/etree/ElementPath.py", line 370, in iterfind
    selector = _cache[cache_key]
               ~~~~~~^^^^^^^^^^^
KeyError: ('./b[last()]', ('', 'http://www.example.com/default-schema'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/lukas/miniforge3/envs/roads/lib/python3.12/xml/etree/ElementPath.py", line 405, in find
    return next(iterfind(elem, path, namespaces), None)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/lukas/miniforge3/envs/roads/lib/python3.12/xml/etree/ElementPath.py", line 384, in iterfind
    selector.append(ops[token[0]](next, token))
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/lukas/miniforge3/envs/roads/lib/python3.12/xml/etree/ElementPath.py", line 315, in prepare_predicate
    raise SyntaxError("unsupported function")
SyntaxError: unsupported function
>>> ET.XML('<a xmlns="http://www.example.com/default-schema"><b/><b/></a>').find("./b", {"": "http://www.example.com/default-schema"})
<Element '{http://www.example.com/default-schema}b' at 0x750110149b20>
>>>

• searching by integer position yields None
• searching with the predicate [last()] fails with "unsupported function"

This works fine when no namespaces are involved:

\>>> ET.XML('<a><b/><b/></a>').find("./b[1]")
<Element 'b' at 0x7501101498a0>
>>> ET.XML('<a><b/><b/></a>').find("./b[last()]")
<Element 'b' at 0x7501101499e0>
>>> 

With namespaces I would expect similar results.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

• gh-132822

Commencez par reproduire les exemples de namespaces avec xml.etree.ElementTree, en comparant les prédicats positionnels et last() avec le comportement montré pour le XML sans namespace. Suivez l’implémentation de la recherche de chemins de ElementTree utilisée par find() ; le travail est terminé lorsque les deux prédicats renvoient les éléments attendus avec un namespace par défaut. Un PR associé, gh-132822, existe déjà.