Bug 309730 – Deleting next sibling node while replacing this node stops the replacement being processed

• Component: DOM
• Status: RESOLVED FIXED

[Barry Pollard]

Take this HTML:

```html
    <div id="to-be-replaced"></div><span id="to-be-removed"></span>

    <template id="my-template">
        <span>New </span>
        <script id="removal-script">
            document.querySelector("#to-be-removed").remove();
        </script>
        <span>content</span>
    </template>

    <script>
        const template = document.querySelector('#my-template');
        document.querySelector('#to-be-replaced').replaceWith(template.content.cloneNode(true));
    </script>
```

This should replace the `<div id="to-be-replaced"></div>` with the contents of the template, and the `<script>` in that should remove the following `<span id="ref"></span>`, and so we should be left with "New content" (with a hidden `<script>` in between those two words).

This works in Chrome and Firefox.

However in Safari, when it inserts the script, and deletes the `<span>`, Safari stops processing the rest of the `replaceWith` and so you're left with "New" (and the hidden script) but without "Content".

However, if you add any whitespace between the `<div>` and the `<span>`, then it all works fine. The bug only happens when the next sibling is removed mid-replacement.

Additionally, if you wrap the children of the `<template>` into a single `<div>` element it also works.

You can see this in the test cases here: https://www.tunetheweb.com/experiments/safari-node-replacement-bug/

[Ryosuke Niwa]

The `script` element now uses the "post-connection steps" in https://dom.spec.whatwg.org/#concept-node-insert.

Whereas WebKit runs scripts as they get inserted, the spec delays the execution until all nodes are inserted.

To match the spec's behavior, we'd need to change delay childrenChanged and didFinishInsertingNode who inserting a document fragment.

[Ryosuke Niwa]

This has been fixed by https://commits.webkit.org/309388@main.

[Ryosuke Niwa]

Pull request: https://github.com/WebKit/WebKit/pull/60755

[EWS]

Committed 309411@main (c495217439eb): <https://commits.webkit.org/309411@main>

Reviewed commits have been landed. Closing PR #60755 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/172753019>