CONTRIBUTING.md

Contributing to Rust-Lightning

The rust-lightning project operates an open contributor model where anyone is welcome to contribute towards development in the form of peer review, documentation, testing and patches.

Anyone is invited to contribute without regard to technical experience, "expertise", OSS experience, age, or other concern. However, the development of cryptocurrencies demands a high-level of rigor, adversarial thinking, thorough testing and risk-minimization. Any bug may cost users real money. That being said, we deeply welcome people contributing for the first time to an open source project or pick up Rust while contributing. Don't be shy, you'll learn.

For the project Code of Conduct, see our website.

Communication Channels

Communication about the development of LDK and rust-lightning happens primarily on the LDK Discord in the #ldk-dev channel. Additionally, live LDK development meetings are held every other Monday 17:00 UTC in the LDK Dev Jitsi Meeting Room. Upcoming events can be found in the LDK calendar.

Contributors starting out with the Rust language are welcome to discuss and ask for help in the #rust-101 channel on LDK Discord.

Discussion about code base improvements happens in GitHub issues and on pull requests.

The LDK roadmap is tracked here.

Major milestones are tracked here.

Getting Started

First and foremost, start small.

This doesn't mean don't be ambitious with the breadth and depth of your contributions but rather understand the project culture before investing an asymmetric number of hours on development compared to your merged work.

Browsing through the meeting minutes is a good first step. You will learn who is working on what, how releases are drafted, what are the pending tasks to deliver, where you can contribute review bandwidth, etc.

Even if you have an extensive open source background or sound software engineering skills, consider that the reviewers' comprehension of the code is as much important as technical correctness.

It's very welcome to ask for review on LDK Discord. And also for reviewers, it's nice to provide timelines when you hope to fulfill the request while bearing in mind for both sides that's a "soft" commitment.

If you're eager to increase the velocity of the dev process, reviewing other contributors work is the best you can do while waiting review on yours.

Also, getting familiar with the glossary will streamline discussions with regular contributors.

Contribution Workflow

The codebase is maintained using the "contributor workflow" where everyone without exception contributes patch proposals using "pull requests". This facilitates social contribution, easy testing and peer review.

To contribute a patch, the workflow is as follows:

1. Fork Repository
2. Create topic branch
3. Commit patches

In general commits should be atomic and diffs should be easy to read. For this reason do not mix any formatting fixes or code moves with actual code changes. Further, each commit, individually, should compile and pass tests, in order to ensure git bisect and other automated tools function properly.

When adding a new feature, like implementing a BOLT spec object, thought must be given to the long term technical debt. Every new features should be covered by functional tests.

When refactoring, structure your PR to make it easy to review and don't hesitate to split it into multiple small, focused PRs.

The Minimum Supported Rust Version (MSRV) currently is 1.63.0 (enforced by our GitHub Actions). We support reading serialized LDK objects written by any version of LDK 0.0.99 and above. We support LDK versions 0.0.113 and above reading serialized LDK objects written by modern LDK. Any expected issues with upgrades or downgrades should be mentioned in the changelog.

Commits should cover both the issue fixed and the solution's rationale. These guidelines should be kept in mind.

To facilitate communication with other contributors, the project is making use of GitHub's "assignee" field. First check that no one is assigned and then comment suggesting that you're working on it. If someone is already assigned, don't hesitate to ask if the assigned party or previous commenters are still working on it if it has been awhile.

Any changes that have nontrivial backwards compatibility considerations should have an entry added in the pending_changelog folder which includes the CHANGELOG entries that should be added in the next release.

Peer review

Anyone may participate in peer review which is expressed by comments in the pull request. Typically reviewers will review the code for obvious errors, as well as test out the patch set and opine on the technical merits of the patch. PR should be reviewed first on the conceptual level before focusing on code style or grammar fixes.

Coding Conventions

Use tabs. If you want to align lines, use spaces. Any desired alignment should display fine at any tab-length display setting. We use rustfmt to establish uniform coding standards throughout the codebase. Please run

./contrib/run-rustfmt.sh

before committing and pushing any changes, as compliance will also be checked and enforced by our CI scripts.

Our CI enforces clippy's default linting settings. This includes all lint groups except for nursery, pedantic, and cargo in addition to allowing the following lints: erasing_op, never_loop, if_same_then_else.

If you use rustup, feel free to lint locally, otherwise you can just push to CI for automated linting.

rustup component add clippy
cargo clippy

Significant structures that users persist should always have their serialization methods (usually Writeable::write and ReadableArgs::read) begin with write_ver_prefix!()/read_ver_prefix!() calls, and end with calls to write_tlv_fields!()/read_tlv_fields!().

Updates to the serialized format which has implications for backwards or forwards compatibility must be included in release notes.

Security

Security is the primary focus of rust-lightning; disclosure of security vulnerabilities helps prevent user loss of funds. If you believe a vulnerability may affect other Lightning implementations, please inform them.

You can find further information on submitting (possible) vulnerabilities in the security policy.

Testing

Related to the security aspect, rust-lightning developers take testing very seriously. Due to the modular nature of the project, writing new functional tests is easy and good test coverage of the codebase is an important goal. Refactoring the project to enable fine-grained unit testing is also an ongoing effort.

Fuzzing is heavily encouraged: you will find all related material under fuzz/

Mutation testing is work-in-progress; any contribution there would be warmly welcomed.

C/C++ Bindings

You can learn more about the C/C++ bindings that are made available by reading the C/C++ Bindings README. If you are not using the C/C++ bindings, you likely don't need to worry about them, and during their early experimental phase we are not requiring that pull requests keep the bindings up to date (and, thus, pass the bindings_check CI run). If you wish to ensure your PR passes the bindings generation phase, you should run the genbindings.sh script in the top of the directory tree to generate, build, and test C bindings on your local system.

Going further

You may be interested by Jon Atack's guide on How to review Bitcoin Core PRs and How to make Bitcoin Core PRs. While there are differences between the projects in terms of context and maturity, many of the suggestions offered apply to this project.

Overall, have fun :)