rrweb [Bug]: CSS `all: unset` incorrectly expands in `events.json` recording

Preflight Checklist

[X] I have searched the issue tracker for a bug report that matches the one I want to file, without success.

What package is this bug report for?

rrweb

Version

v2.0.0-alpha.11

Expected Behavior

When all:unset is set, I expect no change to my rendered webpage.

Actual Behavior

When all:unset is encountered, the css class marks every element as unset except for those set

e.g. if we have

.class1 {
   all: unset;
   padding: 10px;
}

becomes this in the events.json snapshot (making the replayer show an inaccurate screenshot):

.class1 {
    color-scheme: unset;
    forced-color-adjust: unset;
    mask: unset;
    math-depth: unset;
    position: unset;
    position-anchor: unset;
   /* ...truncated... */
   padding: 10px; // this is set
   padding-inline: unset; // this is "unset", which incorrectly overwrites the above
   /* ...truncated ...*/
}

which overrides padding-left and padding-right incorrectly compared to the original css. If the all:unset was done in order (i.e. insert all variables as unset, then not resort them into alphabetical order), it would've been correct.

Steps to Reproduce

Run rrweb snapshot on the following webpage, and then run it through the replayer:

<html>
  <head>
    <style>
      .class1 {
        all: unset;
        padding: 4px; border: 1px solid black;
      }
    </style>
  </head>
  <body>
    <div class="class1">
      Hello
    </div>
  </body>
</html>

it should look like this:

but the replayer shows (notice the padding + border removed):

this is because the all:unset expands incorrectly with padding-inline: unset overriding padding: 4px for padding-left/padding-right and border-inline: unset overriding border: 1px for border-left/right:

Testcase Gist URL

https://rrwebdebug.com/play/index.html?url=https%3A%2F%2Fgist.github.com%2Fotan%2F334b83336c7872c750bb5ef3357435fb&version=2.0.0-alpha.11&virtual-dom=on&play=on

Additional Information

No response

Jun 11 '24 05:06 otan

Diving into this a bit more, it seems it's because of the way we read cssRules to stringifyStylesheet.

Running document.styleSheets[0].cssRules[0].cssText on the html page linked above yields the same erroneous output we see above:

which explains the results. the bug indeed only happens when rrweb records on chrome but not safari

Jun 11 '24 12:06 otan

Here is the Chrome issue, note that it's 6+ years old, so is not a priority at the moment.

repro https://jsfiddle.net/md1erq6k/9/

I'll work on a fix tomorrrow on rrweb side of things.

Nov 25 '24 20:11 billyvg

@billyvg I'm interested in a resolution for this issue. Do you know if it was fixed and released?

May 23 '25 22:05 andrewortwein