Contributing

Code of Conduct

Contributors to Tree-sitter should abide by the Contributor Covenant.

Developing Tree-sitter

Prerequisites

To make changes to Tree-sitter, you should have:

1. A C compiler, for compiling the core library and the generated parsers.
2. A Rust toolchain, for compiling the Rust bindings, the highlighting library, and the CLI.
3. Node.js and NPM, for generating parsers from grammar.js files.
4. Either Emscripten, Docker, or podman for compiling the library to WASM.

Building

Clone the repository:

git clone https://github.com/tree-sitter/tree-sitter
cd tree-sitter

Optionally, build the WASM library. If you skip this step, then the tree-sitter playground command will require an internet connection. If you have Emscripten installed, this will use your emcc compiler. Otherwise, it will use Docker or Podman:

cd lib/binding_web
npm install # or your JS package manager of choice
npm run build

Build the Rust libraries and the CLI:

cargo build --release

This will create the tree-sitter CLI executable in the target/release folder.

If you want to automatically install the tree-sitter CLI in your system, you can run:

cargo install --path cli

If you're going to be in a fast iteration cycle and would like the CLI to build faster, you can use the release-dev profile:

cargo build --release --profile release-dev
# or
cargo install --path cli --profile release-dev

Testing

Before you can run the tests, you need to fetch some upstream grammars that are used for testing:

cargo xtask fetch-fixtures

To test any changes you've made to the CLI, you can regenerate these parsers using your current CLI code:

cargo xtask generate-fixtures

Then you can run the tests:

cargo xtask test

Similarly, to test the WASM binding, you need to compile these parsers to WASM:

cargo xtask generate-fixtures --wasm
cargo xtask test-wasm

Debugging

The test script has a number of useful flags. You can list them all by running cargo xtask test -h. Here are some of the main flags:

If you want to run a specific unit test, pass its name (or part of its name) as an argument:

cargo xtask test test_does_something

You can run the tests under the debugger (either lldb or gdb) using the -g flag:

cargo xtask test -g test_does_something

Part of the Tree-sitter test suite involves parsing the corpus tests for several languages and performing randomized edits to each example in the corpus. If you just want to run the tests for a particular language, you can pass the -l flag. Additionally, if you want to run a particular example from the corpus, you can pass the -e flag:

cargo xtask test -l javascript -e Arrays

Published Packages

The main tree-sitter/tree-sitter repository contains the source code for several packages that are published to package registries for different languages:

• Rust crates on crates.io:

  • tree-sitter — A Rust binding to the core library
  • tree-sitter-highlight — The syntax-highlighting library
  • tree-sitter-cli — The command-line tool

• JavaScript modules on npmjs.com:

  • web-tree-sitter — A WASM-based JavaScript binding to the core library
  • tree-sitter-cli — The command-line tool

There are also several other dependent repositories that contain other published packages:

• tree-sitter/node-tree-sitter — Node.js bindings to the core library, published as tree-sitter on npmjs.com
• tree-sitter/py-tree-sitter — Python bindings to the core library, published as tree-sitter on PyPI.org.
• tree-sitter/go-tree-sitter — Go bindings to the core library, published as tree_sitter on pkg.go.dev.

Developing Documentation

Our current static site generator for documentation is mdBook, with a little bit of custom JavaScript to handle the playground page. Most of the documentation is written in Markdown, including this file! You can find these files at docs/src. If you'd like to submit a PR to improve the documentation, navigate to the page you'd like to edit and hit the edit icon at the top right of the page.

Prerequisites for Local Development

To run and iterate on the docs locally, the mdbook CLI tool is required, which can be installed with

cargo install mdbook

You might have noticed we have some fancy admonitions sprinkled throughout the documentation, like the note above. These are created using mdbook-admonish, a preprocessor for mdBook. As such, this is also a requirement for developing the documentation locally. To install it, run:

cargo install mdbook-admonish

Once you've installed it, you can begin using admonitions in your markdown files. See the reference for more information.

Spinning it up

Now that you've installed the prerequisites, you can run the following command to start a local server:

cd docs
mdbook serve --open

mdbook has a live-reload feature, so any changes you make to the markdown files will be reflected in the browser after a short delay. Once you've made a change that you're happy with, you can submit a PR with your changes.

Improving the Playground

The playground page is a little more complicated, but if you know some basic JavaScript and CSS you should be able to make changes. The playground code can be found in docs/src/assets/js/playground.js, and its corresponding css at docs/src/assets/css/playground.css. The editor of choice we use for the playground is CodeMirror, and the tree-sitter module is fetched from here. This, along with the wasm module and wasm parsers, live in the .github.io repo.