A Kotlin Multiplatform CSS lexer and parser that produces a fully navigable Abstract Syntax Tree (AST) with source-position tracking.

KSS tokenizes and parses CSS following the W3C CSS Syntax Level 3 specification, providing precise character offsets for every token and AST node. It runs on JVM, macOS, Linux, JS, and WebAssembly.

// Use the BOM for version alignment
dependencies {
    implementation(platform("dev.tonholo.kss:kss-bom:1.0.2"))
    implementation("dev.tonholo.kss:kss-parser")  // includes core + lexer transitively
}

dependencies {
    implementation(platform("dev.tonholo.kss:kss-bom:1.0.2"))
    implementation("dev.tonholo.kss:kss-parser")
}

In your module.yaml:

dependencies:
    - dev.tonholo.kss:kss-parser:1.0.2

Or with individual modules:

dependencies:
    - dev.tonholo.kss:kss-core:1.0.2
    - dev.tonholo.kss:kss-lexer:1.0.2

import dev.tonholo.kss.lexer.css.CssTokenizer

val css = "body { color: red; }"
val tokens = CssTokenizer().tokenize(css)

for (token in tokens) {
    println("${token.kind} [${token.startOffset}..${token.endOffset}]")
}

import dev.tonholo.kss.lexer.css.CssTokenizer
import dev.tonholo.kss.parser.ast.css.CssParser
import dev.tonholo.kss.parser.ast.css.consumer.CssConsumers

val css = "body { color: red; }"
val tokens = CssTokenizer().tokenize(css)
val consumers = CssConsumers(css)
val styleSheet = CssParser(consumers).parse(tokens)

// Navigate the AST
for (child in styleSheet.children) {
    println(child)
}

The project includes a Compose Multiplatform demo app — a CSS AST Explorer with a split-pane layout: a syntax-highlighted CSS editor on the left and an interactive AST tree viewer on the right, with bidirectional synchronization.

./amper run -m demo/desktop

Requires Node.js (>= 18) and npm:

./scripts/run-web.sh

This builds the wasmJs module, extracts the Skiko runtime, installs npm dependencies, and starts a Vite dev server at http://localhost:3000.

KSS uses the Amper build system.

# Build all modules
./amper build

# Run tests
./amper test

# Run code quality checks (ktlint + detekt)
./scripts/check.sh

# Auto-format with ktlint
./scripts/check.sh format

• JDK 17+ (for building)
• Node.js 18+ and npm (for the web demo only)
• Amper is bootstrapped automatically via the included wrapper scripts

See CONTRIBUTING.md for guidelines on how to contribute.

This project is licensed under the MIT License.