Replace CSSOM so new CSS features are supported

[rockisch]

Hi,

I noticed that currently linkedom fails to parse styles with nested CSS rules. Here's a sample code:

import {parseHTML} from "linkedom";

const doc = parseHTML(`
<style>
	.parent { .child { color: red; }}
</style>
`).document;
console.log(doc.children[0].sheet);

Looking into it, it seems like this is an issue with CSSOM, which makes sense considering that project stopped receiving updates 5 years ago and is marked as unmaintained. Although I didn't check, I assume other kinds of 'modern' CSS rules will also raise an exception when parsed.

I would like to know if there is interest in replacing it with an up-to-date CSS parser implementation.

Looking online, I found a benchmark that shows that a few other CSS parsers more or less match the performance of CSSOM, which I know is an important factor for this project.

If this is desired I can take a look into changing the backing implementation, probably trying the projects in the order they appear in that benchmark (I don't know which of those provides the functionalities linkedom requires).

[WebReflection]

I would like to know if there is interest in replacing it with an up-to-date CSS parser implementation.

I've tried to find successors and nobody showed up, I love this library with all my heart and yet I have zero time (it's been a while I have zero time, almost like I work on something else and I have a 4yo daughter, which I do 😅) so the answer to "would you like to improve this?" is gonna be yes but I won't personally do that ... maybe I should put this in maintenance mode, also I wrote smaller/simpler variants I use on occasions so ... is the community or even AI able to step up and provide valuable MRs to this project? Yes? Awesome, bring those in! No? I am afraid even the reading-to-approval time is super constrained these days and I can't keep up the Web pace, 'cause I do in other areas, but not in this "mocking or testing" world!

[rockisch]

I get you, I myself had to 'orphan' a few side projects of mine, and none of them being even close to this size xD

Since even if I worked on it this kind of change would require some non-trivial review from a maintainer (you I guess 😅) I guess I'll just leave it as it is. Although maybe leave the ticket open so people know of this issue and also see the call for maintainers, although maybe that can be added to the README as well ('SEMI-DEPRECATED: Looking for maintainers' or smt like that?)

[WebReflection]

This one involves little logic changes to me, it’s a path I trust occasionally but not the most important one (it’s a side channel to the parsing path) so take your time, I’ll review it, code coverage is there to ensure no regression, more tests are needed to succeed in the MR! If it’s ok, go ahead, I’ll do my best approving once the steps are there 🥳

[philipp-classen]

This fork seems more active: https://github.com/rrweb-io/CSSOM

Maybe it is also an option? Last updated in Oct, 2024. And they also have some fixes regarding nested CSS styles (e.g. rrweb-io/CSSOM#4).

[rockisch]

@philipp-classen that fork adds support specifically for 'nested at-rules', which is not a generic solution for any kind of nested rule (I checked it before opening this issue).