v0.8.10 errors with "Cannot read properties of null (reading 'localName')"

[XhmikosR]

Describe the bug

Cannot read properties of null (reading 'localName')

Expected behavior

No errors

Runtime & Version:

xmldom version: > 0.8.8, e.g 0.8.10
runtime version: N/A
other related software and version: N/A

Additional context

We hit the issue in svg-sprite and thus in projects that depend on it. Example: https://github.com/twbs/icons/actions/runs/6935431138/job/18865536634#step:6:22

I had to pin the version to 0.8.8 in svg-sprite so that we don't get these errors. I didn't try v0.8.9, but I could give it a go later if it helps narrow down the problem.

[karfau]

It would be very helpful if you (or someone from svg-sprite) could provide a reproduction with

• an xml/svg snippet that causes the issue
• how exactly xmldom is used to reproduce the error

There usually is a link to a stackblitz template in the bug template which makes this very easy:
https://stackblitz.com/fork/js-xmldom-template?file=index.js

Thx

[XhmikosR]

v0.8.9 also works for what is worth. So, it's the change in v0.8.10 that is a breaking change for us.

Unfortunately, I don't have a StackBlitz and the stacktrace is misleading (because it points to the svg-sprite source code). I'll see if I manage to create a StackBlitz with a reproducible example later.

[XhmikosR]

Specifically, this change is the offending one: 0.8.9...0.8.10#diff-79db8c65cf49002eb2d5d7e81a17f3b73d94db6bb50c0c12f0c9f427aff4b11eL172

-return this[index] || null;
+return index >= 0 && index < this.length ? this[index] : null;

[karfau]

Any xml source and steps to be able to reproduce it are helpful. Could also be a dedicated small GitHub repo that i can clone to reproduce.
The more narrow the setup the better, but it's ok if it still involves svg-sprite

[karfau]

By the way, the change you point to, belongs to the only PR that is included in version 8.10.0:
#514
So most likely svg-sprite is trying to access an element after a DOM manipulation that no longer exists in the DOM.
Earlier versions didn't properly clean up in such cases, so that it was possible to access elements behind the index indicated by the updated length attribute.

And after reading the history of events in.the related issues an PRs, I checked if there is any difference in what is returned by Object.keys(element.childNodes)
in the different versions in question, and i can not see a difference in behavior:
https://stackblitz.com/edit/js-xmldom-template-b5bsdq?file=index.js,package.json
It is always ["0","1","length"]
But if course if you take the the keys in the beginning of the loop and iterate over them while they are modified and you keep iterating over them without checking that you get something back, it will not work.