Expose low level APIs of format_as_xml

[yf-yang]

Description

format_as_xml is great and handy. However it has limitations that item_tag applies to all the nested levels.

Would you consider exposing low level APIs to convert dict/list to ElementTree.Element? Maybe provide 3 utilities:

1. dict/list to xml str (format_as_xml)
2. dict/list to Element
3. Element to str

With such an approach, developers can control element tree themselves.

References

No response

[DouweM]

@yf-yang Can you see if #2313 will already do what you're looking for, by taking element names from the types themselves?

[yf-yang]

Hmm not so sure. I just expect a lightweight dict/list wrapper but I am OK with pydantic model solution.
However, seems the code still use item_tag for iterable of pydantic models, instead of the model's own name, right?

[DouweM]

Hmm not so sure. I just expect a lightweight dict/list wrapper but I am OK with pydantic model solution.

Low level XML generation utils seem a bit out of scope for Pydantic AI, while a high-level "turn any data (e.g. Pydantic model) into XML" convenience feature seems like it fits better.

However, seems the code still use item_tag for iterable of pydantic models, instead of the model's own name, right?

I don't think so; in the test, this:

                    items=[
                        DataItem1('a'),
                        DataItem1(source='xx'),
                    ],

becomes this:

      <items>
        <DataItem1>
          <id>a</id>
          <source>none</source>
        </DataItem1>
        <DataItem1>
          <id>null</id>
          <source>xx</source>
        </DataItem1>
      </items>

[yf-yang]

Sounds good