Removing nodes does not nullify _nodePtr of all freed nodes

[afn]

The (xmlFreeNode())[https://gnome.pages.gitlab.gnome.org/libxml2/html/tree_8h.html#ad330960328f909614fd956bd491d5d9c] function frees all children of the specified node, but the (remove() method of XmlNode)[https://github.com/jameslan/libxml2-wasm/blob/01fc960fa0af28dc8c6499f530ed37d71da23dc3/src/nodes.mts#L155-L162] only nullifies its own _nodePtr, not that of its descendants. This can cause issues when calling remove() on a node that has already been removed, e.g.:

let doc, xpath;

try {
  doc = XmlDocument.fromString('<root><a id="1"><a id="2"/></a></root>');
  xpath = XmlXPath.compile('//a');
  for(const node of doc.eval(xpath) as XmlNode[]) {
    node.remove(); // Throws an error when it tries to remove <a id="2">
  }
}
finally {
  xpath?.dispose();
  doc?.dispose();
}

One possible sketch of a solution:

1. Track all XmlNode instances in a weak map (either using Disposable, or if there's a reason not to do this, then a similar implementation)
2. In remove(), walk the subtree rooted at the current node, and for each instance of each descendant node, nullify its _nodePtr.

Thoughts?

[jameslan]

In libxml2, some objects (e.g. xmlNode and its subclasses) are owned by another object, while others are not (e.g. xmlDoc).

When the owner object changes—for example, when a node is removed—the pointers to internally owned objects may become invalid. This is expected behavior in libxml2.

In libxml2-wasm, the JS objects are merely thin wrappers around the underlying C pointers, so they follow the same ownership and lifetime semantics. There is no additional safety layer on top.

Your example demonstrates exactly this behavior. If the same logic were written in C using libxml2, it would fail in the same way.

The correct usage pattern is to re-query the node each time, instead of holding on to a stale reference, for example:

while ((node = doc.get('xxx')) != null) {
    node.remove();
}

This ensures the pointer is always valid with respect to the current document state.