accent-sass

Sass infrastructure for Rust, at parity with dart-sass.

accent-sass compiles Sass to CSS in pure Rust, with no Node and no libsass. It is a fork of connorskees/grass that carries the modern Dart Sass features upstream has not released, so that a Rust program can build real-world stylesheets -- Bulma, Pico, Foundation, USWDS -- without shelling out to another toolchain.

Parity with dart-sass is the goal, not an aspiration to approximate it: a deviation from the reference implementation is a bug, except in error messages and error spans.

It is built for and maintained alongside Accent CMS, the single-binary markdown CMS, which compiles theme Sass in-process through this crate. It is a general-purpose library, and does not depend on Accent.

Install

accent-sass = "0.15.0"

To track work that has not been released yet, pin a git revision instead:

accent-sass = { git = "https://github.com/zoosky/accent-sass.git", rev = "<commit>" }

Use

As a library:

fn main() -> Result<(), Box<accent_sass::Error>> {
    let css = accent_sass::from_string(
        "a { b { color: &; } }".to_owned(),
        &accent_sass::Options::default(),
    )?;
    assert_eq!(css, "a b {\n  color: a b;\n}\n");
    Ok(())
}

The API is deliberately small: from_string, from_path, and an Options builder.

As a binary, intended as a drop-in for the sass executable:

accent-sass input.scss

Status

13,813 of 14,218 sass-spec tests pass against the pinned spec revision (measured 2026-09-05). CI compiles Bulma, Pico, Foundation and USWDS with both engines on every commit and fails on any colour-value difference; that corpus currently shows none.

Job	Gates?	What it checks
`tests`, `fmt`, `clippy`	yes	the crate's own suite, on the 1.96.1 MSRV
`frameworks`	yes	the four-framework corpus, gated on colour values
`bootstrap`	advisory	Bootstrap 5.0.2; prints the delta
`sass-spec`	advisory	publishes the spec tallies

What each release changed is in CHANGELOG.md. What is left is in specs/docs/features/, one document per work item, ranked by the spec tests it unlocks.

accent-sass is not a drop-in replacement for libsass and does not intend to be.

Cargo features

Feature	Default	Effect
`commandline`	yes	build the binary, using clap
`random`	yes	the builtin `random([$limit])` and `unique-id()`
`macro`	no	the `accent_sass::include!` macro, compiling Sass at build time
`nightly`	no	lets `include!` use `proc_macro::tracked_path`

Testing

Running cargo test should be all you need. The crate keeps a suite distinct from sass-spec, following the same philosophy as rust-analyzer, so tests run without ruby and can be more granular than the official spec.

To run the official suite (node >= v14.14.0; does not work on Windows):

git clone https://github.com/zoosky/accent-sass --recursive
cd accent-sass && cargo build --release
cd sass-spec && npm install
npm run sass-spec -- --impl=dart-sass --command '../target/release/accent-sass' \
  --trim-errors --ignore-warning-diffs --ignore-error-diffs

The leniency flags score CSS output and error messages only. Without them a test that differs solely in a missing deprecation warning or in error wording counts as a failure; that gap is sized in specs/docs/features/08-calculation-warnings-and-error-wording.md.

Versioning

Semantic Versioning. While the major version is 0, a breaking change bumps the minor version. Version numbers are this fork's own and do not track upstream grass.

The crates are on the Rust 2024 edition. The minimum supported Rust version is 1.96.1, normalised across the Accent crates; CI gates on it. Raising the MSRV is a minor version bump.

accent-sass targets dart-sass version 1.103.1.