WebReflection / WebReflection/linkedom

Incorrect target reported in all MutationRecords of type `childList`

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Description

Running this code:

import { parseHTML } from "linkedom";
const { document, MutationObserver } = parseHTML(
  "<!doctype html><html><head></head><body>",
);

let mo = new MutationObserver((records) => {
  let { nodeName } = records[0].target;
  console.assert(nodeName === "BODY", `Expected BODY, got ${nodeName}.`);
});

mo.observe(document, { subtree: true, childList: true });

document.body.appendChild(document.createTextNode(""));

results in this error:

Assertion failed: Expected BODY, got #document.

If I'm reading it correctly, it looks like the target for a mutation is always reported as the node passed to observe (at least for childList) which is incorrect; for the childList MutationRecord type, the target should be the parentNode of the inserted/removed node(s).

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  1. Read the whole issue, then the project's contributing guide.
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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in esm/interface/mutation-observer.js at the linked location and run the reproduction using parseHTML and MutationObserver. Verify that a childList MutationRecord reports the parent node of the inserted or removed nodes as its target, so the assertion observes BODY rather than #document.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript
Domain
web-dev
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
50/100

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