Conversion from XML to JSON array inconsistency

[eugenevd]

Describe the bug
Given XML with multiple rows:

    <data>
        <row id="0">
            <TYPE>X</TYPE>
            <ID>123</ID>            
        </row>
        <row id="1">
            <TYPE>Y</TYPE>
            <ID>321</ID>           
        </row>
    </data>   

produces JSON with row as array.

vs XML with a single row:

    <data>
        <row id="0">
            <TYPE>X</TYPE>
            <ID>123</ID>            
        </row>
    </data>   

produced JSON with row not as an array.

To Reproduce

const expect = chai.expect;
const { convert } = require('xmlbuilder2');
describe('Test XML to JSON arrays', function ()
{
    it('Multiple items in XML should result in JSON array', async function()
    {
        const XMLmulti = '<export><data><row id="0"><TYPE>X</TYPE><ID>123</ID></row><row id="1"><TYPE>Y</TYPE><ID>321</ID></row></data></export>';
        let JSONmulti = convert(XMLmulti, { format: "object" });
        expect(JSONmulti.export.data.row.length).to.equal(2);
    });
    it('Single item in XML should result in JSON array', async function()
    {
        const XMLsingle = '<export><data><row id="0"><TYPE>X</TYPE><ID>123</ID></row></data></export>';
        let JSONsingle = convert(XMLsingle, { format: "object" });
        expect(JSONsingle.export.data.row.length).to.equal(1);
    });
});

Expected behavior
Result:
{ "export": { "data": { "row": { "@id": "0", "TYPE": "X", "ID": "123" } } } }
Expected:
{ "export": { "data": { "row": [{ "@id": "0", "TYPE": "X", "ID": "123" }] } } }

Version:

• node.js: [12.18.0]
• xmlbuilder2 [2.1.6]

[oozcitak]

This would force elements with single child nodes to always create arrays. I don't think we want this:

{
  root: [
    {
      child: [
        {
          grandchild: [
            {
              "text"
            }
          ]
        }
      ]
    }
  ]
}

Your expected output should also be:

Expected:
{ "export": [{ "data": [{ "row": [{ "@id": "0", "TYPE": "X", "ID": "123" }] }] }] }

as "row", "data" and "export" are all elements with single child nodes.

Is there a reason you want this feature, or is it just for consistency's sake?

[IamRaduB]

Encountering the same issue. It would be great to be able to pass a set of xpaths to the converter telling it: these nodes should be arrays.

[oozcitak]

pass a set of xpaths to the converter

@IamRaduB If I am understanding this correctly, you want to be able to determine which element nodes should have their contents to be always grouped into an array. I am guessing you are post-processing the resulting JS object. Maybe it would be better to allow customizing the converter; so you can tweak the output as you require. Can you describe the use case a bit?

[gpyshenko]

I support this proposal, it very useful. It is convenient to get the expected result.

[eugenevd]

For me it's about consistency. I retrieve XML data from a SOAP service. After converting to JSON, I process it. The code would be much simpler if I knew I'll always have an array where expected (array with 0,1 or more elements).

[leog]

I too bumped with this requirement @oozcitak. Maybe using the element custom parser to enforce array treatment for selected element names? 🤔

Otherwise in order to let the dev choose, the verbose option could be a boolean or a list of keys to check whether the array treatment should apply or not 🤩

[oozcitak]

@leog I started working on custom serializers. You can track of the progress at #47