tree-sitter4j

tree-sitter API for Java using WebAssembly.

This library brings tree-sitter parsing capabilities to Java by compiling tree-sitter and its language grammars to WebAssembly and running them through Chicory, a pure-Java WASM runtime. No JNI or native binaries required.

Modules

Tree-sitter4j is a Maven multi-module project:

core

The Java module that provides the public API. It contains:

• TreeSitter -- factory for creating parser instances (manages the WASM module lifecycle via Chicory)
• TreeSitterParser -- wraps a tree-sitter parser; set a language, parse a string, get a tree
• TreeSitterTree / TreeSitterNode -- navigate the resulting AST (node types, children, S-expressions, byte ranges, ...)
• Language -- enum of available grammars (see below)

wasm-build

The Rust/WebAssembly module. It compiles tree-sitter core and the grammar crates listed in Cargo.toml into a single tree-sitter.wasm binary. The Makefile handles downloading WASI SDK and Binaryen, building, and optimizing the WASM output.

Supported languages

The following tree-sitter grammars are compiled into the WASM module and exposed through the Language enum:

Language	Crate	Version	Repository
core	tree-sitter	0.26.9	[tree-sitter](https://docs.rs/tree-sitter/0.26.9/tree_sitter/
JSON	tree-sitter-json	0.24.8	tree-sitter-json
Java	tree-sitter-java	0.23.5	tree-sitter-java
Properties	tree-sitter-properties	0.3.0	tree-sitter-properties
HTML	tree-sitter-html	0.23.2	tree-sitter-html
XML	tree-sitter-xml	0.7.0	tree-sitter-xml
Markdown	tree-sitter-md	0.5.3	tree-sitter-md
YAML	tree-sitter-yaml	0.7.2	tree-sitter-yaml

To add a new language, add the grammar crate to wasm-build/Cargo.toml, register it in wasm-build/src/lib.rs with a new ID, and add the corresponding entry to the Language enum in core.

Usage

try (TreeSitter ts = TreeSitter.create();
     TreeSitterParser parser = ts.newParser()) {

    parser.setLanguage(Language.JAVA);

    try (TreeSitterTree tree = parser.parseString("class Foo {}")) {
        TreeSitterNode root = tree.rootNode();
        System.out.println(root.toSexp());
    }
}

Building

Prerequisites

• Java 17+
• Maven 3.9+
• Rust toolchain with the wasm32-wasip1 target (only needed to rebuild the WASM binary)

Build tree-sitter4j

If wasm-build/wasm/tree-sitter.wasm is already present (checked into the repo), you only need to run this command:

mvn clean install

Rebuild the WASM binary

If it is needed to rebuild the wasm binary file for whatever reason like to add a new grammar/language, then you will have to perform the following steps:

• Add the new grammar to the Cargo.toml file under the section [dependencies],
• Include the new language id and method to call under the rust file wasm-build/src/lib.rs. see section // --- Language helpers ---,
• Update the README.md file to add the new language ## Supported languages

Then, execute these commands

cd wasm-build
make all

Additionally, include to this new language part of the Enum io.roastedroot.treesitter.Language and rebuild the java core module

public enum Language {
    JSON(0),
    JAVA(1),
    PROPERTIES(2),
    HTML(3),
    XML(4),
    MARKDOWN(5),
    YAML(6);
    // NEWLANGUAGE(7);

NOTE: The Makefile includes the instructions needed to install localy: wasi-sdk and Binaryen !