grass 0.10.8

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This crate aims to provide a high level interface for compiling Sass into plain CSS. It offers a very limited API, currently exposing only 2 functions.

In addition to a library, also included is a binary that is intended to act as an invisible replacement to the Sass commandline executable.

This crate aims to achieve complete feature parity with the dart-sass reference implementation. A deviation from the dart-sass implementation can be considered a bug except for in the following situations:

  • Error messages
  • Error spans
  • Certain aspects of the indented syntax
  • Potentially others in the future



grass has reached a stage where one can be quite confident in its output. For the average user there should not be perceptible differences from dart-sass.

Every commit of grass is tested against bootstrap v5.0.2, and every release is tested against the last 2,500 commits of bootstrap's main branch.

That said, there are a number of known missing features and bugs. The notable features remaining are

indented syntax
@forward and more complex uses of @use
@at-root and @import media queries
@media query merging
/ as a separator in color functions, e.g. rgba(255, 255, 255 / 0)
Infinity and -Infinity
builtin meta function `keywords`

All known missing features and bugs are tracked in #19.

grass is not a drop-in replacement for libsass and does not intend to be. If you are upgrading to grass from libsass, you may have to make modifications to your stylesheets, though these changes should not differ from those you would have to make if upgrading to dart-sass.

Web Assembly

grass experimentally releases a WASM version of the library to npm, compiled using wasm-bindgen. To use grass in your JavaScript projects, just run npm install @connorskees/grass to your package.json. Better documentation for this version will be provided when the library becomes more stable.



(enabled by default): build a binary using clap


(enabled by default): enable the builtin functions random([$limit]) and unique-id()

In the future this feature will be removed when it is no longer necessary to rely on rand for random numbers.


As much as possible this library attempts to follow the same philosophy for testing as rust-analyzer. Namely, all one should have to do is run cargo test to run all its tests. This library maintains a test suite distinct from the sass-spec, though it does include some spec tests verbatim. This has the benefit of allowing tests to be run without ruby as well as allowing the tests more granular than they are in the official spec.

Having said that, to run the official test suite,

git clone --recursive
cd grass
cargo b --release
./sass-spec/sass-spec.rb -c './target/release/grass'

Note: you will have to install ruby, bundler and run bundle install in ./sass-spec/. This might also require you to install the requirements separately for curses.

Alternatively, it is possible to use nodejs to run the spec,

# This script expects node >=v14.14.0. Check version with `node --version`
git clone --recursive
cd grass && cargo b --release
cd sass-spec && npm install
npm run sass-spec -- --command '../target/release/grass'

These numbers come from a default run of the Sass specification as shown above.

TOTAL: 6256