Starlasu Kotlin

Starlasu Kotlin provides the infrastructure for building custom, possibly mutable, Abstract Syntax Trees (ASTs).
It supports both Kotlin and Java, and integrates smoothly with ANTLR, though it can also be used standalone.

Starlasu stands for Star Language Support — a family of libraries available for multiple languages, including Python, TypeScript, and C#.

Starlasu Kotlin (previously called Kolasu) Version Overview

Version	Status	JVM Support	Kotlin Support	Notes
1.5	Maintenance mode	1.8	1.8	Actively maintained for legacy compatibility (Kolasu, com.strumenta.kolasu)
1.6	Dropped	—	—	Internal line, never meant to be adopted
1.7	Current stable	21	2.4	Current release line (main); see the 1.5 → 1.7 migration guide
2.0	Planned	29	—	Future major release

Supported JDKs

Tested with JDK 21 and 25.

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Documentation

• Concepts and Principles: Starlasu documentation — shared across all Starlasu libraries.
• API Reference: Javadoc for Starlasu Kotlin.
• Module and package overviews: the README.md of each module, also included in the generated API docs (./gradlew dokkaGenerateHtml).
• Migrating from Kolasu 1.5: 1.5 → 1.7 migration guide — package rename, renamed/removed types, LionWeb and Starlasu-Specs coordinates.

Modules

All artifacts are published under the com.strumenta.starlasu group.

Artifact	Purpose
starlasu-core	AST model, traversal, transformation, ANTLR-based parsing infrastructure
starlasu-semantics	Symbol resolution: scopes, symbol descriptions, symbol resolver
starlasu-lionweb	Conversion of ASTs and languages to and from LionWeb
starlasu-lionweb-client	Storage of ASTs in a LionWeb repository
starlasu-codebase	A codebase as a set of parsed files
starlasu-javalib	Helpers for using Starlasu Kotlin from Java

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What Is It Used For?

Starlasu is used to implement:

• Parsers
• Editors
• Transpilers
• Code analysis tools

It serves as a general foundation for projects that need to manipulate or generate language structures.

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Key Features

Extend your AST classes from Node to automatically gain:

• Navigation: Traverse, search, and modify the AST with utility methods.
• Printing: Debug-print ASTs and parse trees.
• LionWeb Interoperability: Export ASTs and languages (i.e., metamodels) to LionWeb.
• Name Resolution: Built-in utilities for named elements and reference resolution.
• Automatic Structure Discovery: Starlasu introspects your AST — all properties and tree structure are detected automatically.

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Background

Starlasu began as a small framework to support building languages with ANTLR and Kotlin.
It has since evolved into a modular, cross-language toolkit used at Strumenta in both open-source and commercial projects for transpilers, interpreters, compilers, and related tools.

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Installation

Add the dependency from Maven Central:

dependencies {
    implementation "com.strumenta.starlasu:starlasu-core:1.7.x"
}

Performance benchmarks

The lionweb module contains JMH microbenchmarks for the model-conversion hot paths (importModelFromLionWeb, exportModelToLionWeb, tree traversal).

# Run all benchmarks
./gradlew :lionweb:jmh

# Run a specific class
./gradlew :lionweb:jmh --include "ImportModelBenchmark"

# Run with GCProfiler (allocation tracking) via the fat jar
./gradlew :lionweb:jmhJar
java -jar lionweb/build/libs/lionweb-jmh.jar ImportModelBenchmark

See lionweb/README.md for the full benchmark documentation.

Code Formatting

Format the code using:

./gradlew ktlintFormat

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Projects Using Starlasu / Kolasu

Starlasu (and its predecessor Kolasu) are used in several internal and commercial projects developed at Strumenta.

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Releasing a New Version

If you need to publish a new release:

1. Set up GPG keys

   brew install gnupg
   gpg --gen-key
   

   (no passphrase needed)
   Export your keys:

   gpg --keyring secring.gpg --export-secret-keys > ~/.gnupg/secring.gpg
   

2. Configure credentials
   Add your Sonatype credentials to ~/.gradle/gradle.properties:

   ossrhTokenUsername=your_username
   ossrhTokenPassword=your_password
   

3. Publish the release

   ./gradlew release
   

Releases are handled automatically once triggered.

For detailed setup instructions, see
Publishing your first open-source library with Gradle.