How to Contribute to Wasmer

Thank you for your interest in contributing to Wasmer. This document outlines the expectations for issues and pull requests.

Issues & Feature Requests

Please use the issue template and provide a failing example if possible to help us recreate the issue.

Code Style

Sparse "why" comments. Short single-responsibility functions.

Lint and Format

CI rejects lint and format failures. Run before you push:

make lint

The lint target in the Makefile defines exactly what runs. To apply clippy fixes in bulk:

cargo clippy --all --exclude wasmer-swift --locked --fix --allow-dirty -- -D clippy::all

cargo fmt does not cover lib/wasix/tests/wasm_tests. CI formats those files with rustfmt --edition 2024 directly.

Pull Requests

For large changes, open a GitHub issue first to ensure we can accept the change once it is ready.

• Title format is conventional-commit style with crate or area scopes: fix(Singlepass): ..., feat(wasix): ..., feat!: ... for breaking changes, chore: ..., deps: ....
• PRs are squash-merged to main. The PR template has one # Description section.
• Before you submit: make lint, then cargo test in the crates you touched, then a build of the CLI.
• Do not hand-edit CHANGELOG.md or crate versions. Releases generate both (see dev/release.md).
• macOS and musl CI jobs run on a PR only when the PR has the macos or musl label. If your change touches platform code, add the label.
• Do not commit a submodule pointer bump in an unrelated PR.

Common Build Issues

LLVM Dependency

Didn't find usable system-wide LLVM means LLVM 22 is missing. Either install it or build with ENABLE_LLVM=0. See Building Wasmer from Source for installation instructions.