swc/CONTRIBUTING.md

Contributing to swc

Thank you for your interest in contributing to swc! Good places to start are this document, ARCHITECTURE.md, which describes the high-level structure of swc and E-easy bugs on the issue tracker.

Code of Conduct

All contributors are expected to follow our Code of Conduct.

Bug reports

We can't fix what we don't know about, so please report problems liberally. This includes problems with understanding the documentation, unhelpful error messages, and unexpected behavior.

Opening an issue is as easy as following this link and filling out the fields. Here's a template that you can use to file an issue, though it's not necessary to use it exactly:

<short summary of the problem>

I tried this: <minimal example that causes the problem>

I expected to see this happen: <explanation>

Instead, this happened: <explanation>

I'm using <output of `swc --version`>

All three components are important: what you did, what you expected, what happened instead. Please use https://gist.github.com/ if your examples run long.

Feature requests

Please feel free to open an issue or to send a pr.

Working on issues

If you're looking for somewhere to start, check out the E-easy and E-mentor tags.

Feel free to ask for guidelines on how to tackle a problem on gitter or open a new issue. This is especially important if you want to add new features to swc or make large changes to the already existing code-base. swc's core developers will do their best to provide help.

If you start working on an already-filed issue, post a comment on this issue to let people know that somebody is working it. Feel free to ask for comments if you are unsure about the solution you would like to submit.

We use the "fork and pull" model [described here][development-models], where contributors push changes to their personal fork and create pull requests to bring those changes into the source repository. This process is partly automated: Pull requests are made against swc's master-branch, tested and reviewed. Once a change is approved to be merged, a friendly bot merges the changes into an internal branch, runs the full test-suite on that branch and only then merges into master. This ensures that swc's master branch passes the test-suite at all times.

Your basic steps to get going:

• Fork swc and create a branch from master for the issue you are working on.
• Please adhere to the code style that you see around the location you are working on.
• [Commit as you go][githelp].
• Include tests that cover all non-trivial code. The existing tests in test/ provide templates on how to test swc's behavior in a sandbox-environment. The internal crate testing provides a vast amount of helpers to minimize boilerplate. See testing/lib.rs for an introduction to writing tests.
• Make sure cargo test passes.
• All code changes are expected to comply with the formatting suggested by rustfmt. You can use rustup component add --toolchain nightly rustfmt-preview to install rustfmt and use rustfmt +nightly --unstable-features --skip-children on the changed files to automatically format your code.
• Push your commits to GitHub and create a pull request against swc's master branch.

Getting your development environment set up

After cloning the project there are a few steps required to get the project running.

1. Fetch submodules to pull ECMAScript test suites.

   git submodule update --init --recursive
   

2. Install js dependencies.

   yarn add browserslist
   ( cd ecmascript/transforms; yarn install )
   

3. Setup some environment variables which is required for tests.

   export RUSTFLAGS='--cfg procmacro2_semver_exempt'
   export RUST_BACKTRACE=full
   export PATH="$PATH:$PWD/ecmascript/transforms/node_modules/.bin"
   

4. Run tests

   cargo test --all --all-features
   

Pull requests

After the pull request is made, one of the swc project developers will review your code. The review-process will make sure that the proposed changes are sound. Please give the assigned reviewer sufficient time, especially during weekends. If you don't get a reply, you may poke the core developers on gitter.

A merge of swc's master-branch and your changes is immediately queued to be tested after the pull request is made. In case unforeseen problems are discovered during this step (e.g. a failure on a platform you originally did not develop on), you may ask for guidance. Push additional commits to your branch to tackle these problems.

The reviewer might point out changes deemed necessary. Please add them as extra commits; this ensures that the reviewer can see what has changed since the code was previously reviewed. Large or tricky changes may require several passes of review and changes.

Once the reviewer approves your pull request, a friendly bot picks it up and merges it into swc's master branch.

Contributing to the documentation

TODO

Issue Triage

Sometimes an issue will stay open, even though the bug has been fixed. And sometimes, the original bug may go stale because something has changed in the meantime.

It can be helpful to go through older bug reports and make sure that they are still valid. Load up an older issue, double check that it's still true, and leave a comment letting us know if it is or is not. The [least recently updated sort][lru] is good for finding issues like this.

Contributors with sufficient permissions on the Rust-repository can help by adding labels to triage issues:

• Yellow, A-prefixed labels state which area of the project an issue relates to.

• Magenta, B-prefixed labels identify bugs which are blockers.

• Red, C-prefixed labels represent the category of an issue. In particular, C-feature-request marks proposals for new features. If an issue is C-feature-request, but is not Feature accepted, then it was not thoroughly discussed, and might need some additional design or perhaps should be implemented as an external subcommand first. Ping @swc-projcet/swc if you want to send a PR for an such issue.

• Green, E-prefixed labels explain the level of experience or effort necessary to fix the issue. E-mentor issues also have some instructions on how to get started.

• Purple gray, O-prefixed labels are the operating system or platform that this issue is specific to.

• Orange, P-prefixed labels indicate a bug's priority.

• Light orange, L-prefixed labels indicate language related to the bug.