CONTRIBUTING.md

Contributing

We can use help in a bunch of areas and any help is appreciated. Our GitHub issues serve as a place for any discussion, whether it's bug reports, questions, project direction etc. As the project grows this policy may change.

Our Discord server is open for help and more adhoc discussion. All activity on the Discord is still moderated and will be strictly enforced under the project's Code of Conduct.

Getting Started

Building this project requires a stable Rust toolchain, which can be installed using rustup.

Clone the repository and navigate to the tools directory:

git clone https://github.com/rome/tools
cd tools

Compile all packages and dependencies:

cargo build

Rome can be used via the rome bin in the rome_cli package:

cargo run --bin rome -- --help

Install the required tools

We use Just to run scripts or tasks, to make our life easier.

You can install just using cargo:

cargo install just

But we highly recommend to install it using an OS package manager, so you won't need to prefix the every command with cargo.

Once installed, run the following command install the required tools:

just install-tools

And you're good to go hack with Rome and Rust! 🚀

Testing

To run the tests, just run

just test

If you want to test the tests for a single crate:

just test-crate rome_cli

If you to run only the doctests, you would need to pass an argument to the command:

jus test-doc

In some crates, we use snapshot testing. The majority of snapshot testing is done using insta. insta is already installed by the command just install-tools.

When a snapshot test fails, you can run:

• cargo insta accept to accept all the changes and update all the snapshots;
• cargo insta reject to reject all the changes;
• cargo insta review to review snapshots singularly;

Checks

When you finished your work, and you are ready to commit and open a PR, run the following command:

just ready

This command will run the same commands of the CI: format, lint, tests and code generation. Eventually everything should be "green" 🟢 and commit all the code that was generated.

Language Server and VS Code Extension Development

The Rome language server is the binary crate rome which can be built using the command:

cargo build --bin rome

If benchmarking the language server, be sure to build with the --release flag.

The VS Code extension can be installed from the Marketplace and can be used with a development build of the language server by setting the "rome.lspBin" VS Code setting to the path of the binary:

{
  "rome.lspBin": "/path/to/rome/target/debug/rome"
}

Please note that Windows disallows modifying an executable while it's running, meaning you won't be able to recompile the Rome binary once the extension was activated in your editor.

The server is spawned as a background daemon, and continues to run even after the editor is closed.

To stop the running daemon instance use the rome stop command, with the editor closed as the extension will try to restart it otherwise.

To build the VS Code extension from source, navigate to the editors/vscode directory and run:

npm install
npm run build

This will create a rome_lsp.vsix which you can install into VS Code by running:

npm run install-extension

The "rome.lspBin" VS Code setting will still need to be set as described above.

When the extension is running, it will connect to a daemon server - or it will bootstrap one.

When you apply changes to the binary, you need to do two things:

• compile the binary
• kill the daemon process, so you can spawn a new server session with the new changes

When the daemon is running, it's possible to inspect its logs in the folder rome-logs, placed in the temporary folder of the operative system.

User files

If files specific to your local development environment should be ignored, please add these files to a global git ignore file rather than to a git ignore file within Rome.

You can find more information on this process here.

Node.js development

The npm module npm/rome contains Rome's Node JS API that supports different backends:

• wasm-nodejs (WebAssembly)
• backend-jsonrpc (Connection to the daemon)

For testing and developing, you need to build these packages, following the steps:

1. install wasm-pack globally;
2. run the build command inside the package backend-jsonrpc;
3. run the build and build:wasm-node-dev commands inside the package js-api (folder npm/js-api);
4. run pnpm i inside the package js-api (folder npm/js-api), this will link the WebAssembly bindings and the JSON-RPC bindings;

The tests are run against the compiled files, which means that you need to run the build command after you implemented features/bug fixes.

Website

The Rome website is built with Astro. To start a development server you can run the following commands:

cd website
pnpm install
pnpm start

Generated files

If you work on some parser and you create new nodes or modify existing ones, will need to run a command to update some files that are auto-generated.

cargo codegen grammar

This command will update the syntax of the parsers.

The source is generated from the ungram files.

cargo codegen test

This command will create new tests for your parser. We currently have a neat infrastructure where tests for parser are generated com inline comments found inside the source code. Please read the proper chapter for more information

It's strongly advised to run this command before committing new changes.

cargo codegen analyzer

This command will detect linter rules declared in the analyzers and assists directories in rome_analyze, regenerate the index modules analyzers.rs and assists.rs to import these files, and update the registry builder function in registry.rs to include all these rules. It will also regenerate the configuration of the rules.

cargo coverage

This command will check and report parser conformance against different test suites. We currently target the Official ECMAScript Conformance Test Suite and the Typescript Test Suite

The test suites are included as git submodules and can be pulled using:

git submodule update --init --recursive

Commit messages

Internally, the Rome team adheres as closely as possible to the conventional commit specification. The following this convention encourages commit best-practices and facilitates commit-powered features like change log generation.

The following commit prefixes are supported:

• feat:, a new feature
• fix:, a bugfix
• docs:, a documentation update
• test:, a test update
• chore:, project housekeeping
• perf:, project performance
• refactor:, refactor of the code without change in functionality

Below are examples of well-formatted commits:

feat(compiler): implement parsing for new type of files
fix: fix nasty unhandled error
docs: fix link to website page
test(lint): add more cases to handle invalid rules

Creating pull requests

When creating a new pull request, it's preferable to use a conventional commit-formatted title, as this title will be used as the default commit message on the squashed commit after merging.

Please use the template provided.

Changelog

If the PR you're about to open is a bugfix/feature around Rome, you can add a new line to the CHANGELOG.md, but it's not mandatory.

At the top of the file you will see a [Unreleased] section. The headings divide the sections by "feature", make sure to add a new bullet point.

Here's a sample of the headings:

## [Unreleased]

### CLI
### Configuration
### Editors
### Formatter
### Linter
### Parser
### VSCode
### JavaScript APIs

When you edit a blank section:

• If your PR adds a breaking change, create a new heading called #### BREAKING CHANGES and add bullet point that explains the breaking changes; provide a migration path if possible.
• If your PR adds a new feature of a fix, create a new heading called #### Other changes and add a bullet point that explains the fix or the new feature. Make sure that this new heading appears after the #### BREAKING CHANGES heading.

Writing a changelog line

• Use the present tense, e.g. "Add new feature", "Fix edge case".
• If you fix a bug, please add the link to the issue, e.g. "Fix edge case #4444".
• Whenever applicable, add a code block to show your new changes. For example, for a new rule you might want to show an invalid case, for the formatter you might want to show how the new formatting changes, and so on.

Documentation

If your PR requires some update on the website (new features, breaking changes, etc.), you should create a new PR once the previous PR is successfully merged. When adding new features, the documentation should be part of a new PR, which will be merged right before the release.

Magic comments

• !bench_parser benchmarks the parser's runtime performance and writes a comment with the results;
• !bench_formatter benchmarks the formatter runtime performance and writes a comment with the results;
• !bench_analyzer benchmarks the analyzer runtime performance and writes a comment with the results;

Analyzers and lint rules

To know the technical details of how our analyzer works, how to create a rule and how to write tests, please check our internal documentation page

JavaScript Parser

To know the technical details of how our JavaScript works and how to write test, please check our internal documentation page

Formatter

To know the technical details of how our formatter works and how to write test, please check our internal documentation page

Versioning

We follow the specs suggested by the official documentation:

Odd minor versions are dedicated to pre-releases, e.g. *.5.* . Even minor versions are dedicated to official releases, e.g. *.6.*.

Playground

• run the playground locally