Request: Move to Dart Sass from LibSass

[francisbarton]

Follow-up / branch issue from #27 - LibSass will be deprecated and certain preferred features such as @use (instead of @import are only available in the Dart Sass implementation.
(see here for example).

[wch]

This is definitely on our radar. There are some technical roadblocks in the way, however. With LibSass, we can include the C library in the package, which we know will run on all platforms. With Dart Sass, it requires a JavaScript runtime, which is a bit more challenging to do run on all platforms.

[Teebusch]

Is there any progress on this? I was tripping over the lack of color module and was disappointed to realize that this is because sass uses a SASS-implementation that has been deprecated since 2021.

[gadenbuie]

Hi @Teebusch. This is something we discuss internally on a regular basis. At the moment, the cost-benefit of making the change to Dart Sass is still not worth the considerable and significant effort it would require. We do revisit this regularly.

[Teebusch]

Thank you for your reply @gadenbuie ! It's good to know it is not completely off the table.

The benefit (for us, at least) would be more flexibility in customising bslib. Admittedly, I haven't come across any real blockers.

[wch]

A while back I did some experimentation running dartsass with QuickJS and calling it from R:

https://github.com/wch/sass-quickjs (command line tool)
https://github.com/wch/sassy (R package)

There were still some limitations and bugs at the time, but it's possible that things would work better now if the dependencies were updated. It's also slower than this sass package, which is uses the C libsass library.