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.
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.
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.
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.
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.
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
Projects Using Starlasu / Kolasu
Starlasu (and its predecessor Kolasu) are used in several internal and commercial projects developed at Strumenta.
Releasing a New Version
If you need to publish a new release:
-
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
-
Configure credentials
Add your Sonatype credentials to ~/.gradle/gradle.properties:
ossrhTokenUsername=your_username
ossrhTokenPassword=your_password
-
Publish the release
./gradlew release
Releases are handled automatically once triggered.
For detailed setup instructions, see
Publishing your first open-source library with Gradle.
