facepalm! Found this while troubleshooting scss lint errors. Sass is the only reason for Ruby being in our dev stack ;)
Dart Sass fully sass-spec compatible1.
Next Steps: Ruby Sass
There are a number of intentional behavior differences between Dart Sass and the existing implementations. All of these differences are things we think improve the language, and many of them have also made Dart Sass much easier to implement, but we recognize that they can make migration more difficult. That's why our next priority is updating Ruby Sass by deprecating old behavior or adding new behavior, as necessary.
Our long-term compatibility goal is to ensure, as much as possible, that if a stylesheet compiles without warnings on Ruby Sass, it will also work with Dart Sass. So a substantial portion of our effort in the near future be spent on ensuring all the compatibility issues are fixed. Once that's done, we'll release those changes as part of Ruby Sass 3.5.
Next Steps: Dart Sass
On the Dart front, we have a number of issues outstanding that we want to resolve before we release a stable version of 1.0.0. The majority of these issues are focused on one thing: compatibility with the node-sass render() API. This will make it easy to integrate Dart Sass into existing JS ecosystem tools and workflows, since anything that works with node-sass will automatically work with Dart Sass as well.