Namespace propagation is not correct on serialization

[microshine]

I use this app to generate XML document. fourth element in generated XML doesn't have xmlns:p2="http//second.namespace.com"

const root = new DOMParser().parseFromString(`<root></root>`, "application/xml");

function createElement(tagName, namespace, parent) {
  const el = root.createElementNS(namespace, tagName);
  parent.appendChild(el);
  return el;
}

const namespace1 = "http//first.namespace.com";
const namespace2 = "http//second.namespace.com";

const el1 = createElement("p1:first", namespace1, root.documentElement);
const el2 = createElement("p2:second", namespace2, el1);
const el3 = createElement("p1:third", namespace1, el1);
const el4 = createElement("p2:fourth", namespace2, el3);

const xml = new XMLSerializer().serializeToString(root);
console.log(xml)

XMLDOM output:

<root>
  <p1:first xmlns:p1="http//first.namespace.com">
    <p2:second xmlns:p2="http//second.namespace.com"/>
    <p1:third>
      <p2:fourth/>
    </p1:third>
  </p1:first>
</root>

Chrome output:

<root>
  <p1:first xmlns:p1="http//first.namespace.com">
    <p2:second xmlns:p2="http//second.namespace.com"/>
    <p1:third>
      <p2:fourth xmlns:p2="http//second.namespace.com"/>
    </p1:third>
  </p1:first>
</root>

[awwright]

Wouldn't a second xmlns:p2 (on the p2:fourth element) be redundant, here?

[Phrogz]

Wouldn't a second xmlns:p2 (on the p2:fourth element) be redundant, here?

No, because that namespace declaration applies only to the second element and any descendants.
https://www.w3.org/TR/xml-names/#scoping

[awwright]

Oh for some reason I was reading that completely backwards; yeah, the specified XMLDOM output isn't correct.

[microshine]

I found that commented code

https://github.com/jindw/xmldom/blob/master/dom.js#L1042-L1043

If uncomment that code it works fine

Example 1

const doc = new DOMImplementation().createDocument(null, "root");

doc.documentElement.appendChild(doc.createElement("child"));

const signature1 = doc.createElementNS("https://signature.com", "Signature");
doc.documentElement.appendChild(signature1);
const signature2 = doc.createElementNS("https://signature.com", "Signature");
doc.documentElement.appendChild(signature2);

const xml = new XMLSerializer().serializeToString(doc);
console.log(xml);

// Output
// <root>
//   <child/>
//   <Signature xmlns="https://signature.com"/>
//   <Signature xmlns="https://signature.com"/>
// </root>

Example 2

const doc = new DOMImplementation().createDocument(null, "root");

const p1First = doc.createElementNS("http//first.namespace.com", "p1:first");
const p2Second = doc.createElementNS("http//second.namespace.com", "p2:second");
const p1Third = doc.createElementNS("http//first.namespace.com", "p1:third");
const p2Fourth = doc.createElementNS("http//second.namespace.com", "p2:fourth");

doc.documentElement.appendChild(p1First);
p1First.appendChild(p2Second)
p1First.appendChild(p1Third)
p1Third.appendChild(p2Fourth)

const xml = new XMLSerializer().serializeToString(doc);
console.log(xml);

// Output
// <root>
//   <p1:first xmlns:p1="http//first.namespace.com">
//     <p2:second xmlns:p2="http//second.namespace.com"/>
//     <p1:third>
//       <p2:fourth xmlns:p2="http//second.namespace.com"/>
//     </p1:third>
//   </p1:first>
// </root>