# moss

**Repository Path**: pauljoihn21/moss

## Basic Information

- **Project Name**: moss
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: main
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2026-08-08
- **Last Updated**: 2026-08-09

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# moss

A Sass/SCSS compiler written in Rust.

> **moss** — *Moss is Our Sass, in Rust*

## Features

- Full SCSS parsing (hand-written recursive descent parser)
- SassScript evaluation with all value types (numbers, strings, colors, lists, maps, booleans, null)
- 17 CSS color spaces with conversion matrices and gamut mapping (sRGB, Display P3, A98, ProPhoto, Rec2020, HSL, HWB, Lab, LCH, OKLab, OKLCH, XYZ-D65, XYZ-D50, LMS)
- Built-in functions: `sass:math`, `sass:string`, `sass:list`, `sass:map`, `sass:color`, `sass:meta`, `sass:selector`
- Module system (`@use`, `@forward`, `@import`)
- `@extend` with extension store and transitive resolution
- Control flow: `@if`, `@each`, `@for`, `@while`
- Mixins and functions with `@content`
- CSS serialization (expanded and compressed output)
- Source map generation (v3 format)
- Watch mode with file dependency tracking
- WASM bindings for browser/Node.js usage
- sass-spec integration test runner

## Quick Start

```sh
# Build
cargo build --release

# Compile a file
cargo run --release -- -i input.scss -o output.css

# Watch mode
cargo run --release -- -i input.scss --watch

# Compressed output
cargo run --release -- -i input.scss -o output.css --style compressed
```

## As a Library

```rust
use moss_core::eval;
use moss_core::span::SourceId;

let css = eval::compile_string("a { color: red; }", SourceId(0))?;
println!("{}", css);
// Output: a {
//   color: red;
// }
```

## WASM Usage

```sh
# Build WASM for web
wasm-pack build --target web

# Build WASM for Node.js
wasm-pack build --target nodejs
```

```js
import { Compiler } from "moss";

const compiler = new Compiler();
const result = compiler.compileString("$color: #f00; a { color: $color; }");
console.log(result.css);
// Output: a {
//   color: #f00;
// }
```

### Custom Importers

```js
import { Compiler, WasmImporter } from "moss";

const importer = new WasmImporter({
  canonicalize(url) {
    return new URL(url, baseUrl).href;
  },
  load(url) {
    return { contents: fs.readFileSync(url, 'utf8') };
  }
});

const result = compiler.compileString("@use 'vars';", { importer });
```

## Architecture

```
moss/
├── crates/
│   ├── moss-core/          # Core compiler library
│   │   ├── ast/            # AST types (statements, expressions, selectors, CSS)
│   │   ├── parse/          # Hand-written recursive descent parsers
│   │   ├── eval/           # Evaluator (Sass AST → CSS AST)
│   │   ├── serialize/      # CSS serializer (CSS AST → String)
│   │   ├── value/          # SassScript value types
│   │   │   ├── color.rs    # SassColor, ColorSpace (17 spaces)
│   │   │   └── color_conversions.rs  # 46 conversion matrices
│   │   └── extend/         # @extend implementation
│   ├── moss-cli/           # CLI tool (clap)
│   ├── moss-wasm/          # WASM bindings (wasm_bindgen)
│   └── moss-spec-runner/   # sass-spec integration test runner
└── openspec/               # OpenSpec change tracking
```

## sass-spec Compliance

moss is tested against the [sass-spec](https://github.com/sass/sass-spec) test suite:

```sh
cargo test --test sass_spec
```

Current pass rate: ~63% (1469/2316 tests across 8 suites).

## Development

```sh
# Run all tests
cargo test

# Run clippy
cargo clippy -- -D warnings

# Format code
cargo fmt

# Run sass-spec
cargo test --test sass_spec
```

## License

MIT