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Contributing

Finding ways to help

We label issues that we think are a good opportunity for subsequent contributions as help wanted. These require varying levels of experience with Rust and uv. Often, we want to accomplish these tasks but do not have the resources to do so ourselves.

You don't need our permission to start on an issue we have labeled as appropriate for community contribution as described above. However, it's a good idea to indicate that you are going to work on an issue to avoid concurrent attempts to solve the same problem.

Please check in with us before starting work on an issue that has not been labeled as appropriate for community contribution. We're happy to receive contributions for other issues, but it's important to make sure we have consensus on the solution to the problem first.

Outside of issues with the labels above, issues labeled as bug are the best candidates for contribution. In contrast, issues labeled with needs-decision or needs-design are not good candidates for contribution. Please do not open pull requests for issues with these labels.

Please do not open pull requests for new features without prior discussion. While we appreciate exploration of new features, we will almost always close these pull requests immediately. Adding a new feature to uv creates a long-term maintenance burden and requires strong consensus from the uv team before it is appropriate to begin work on an implementation.

Use of AI

We require all use of AI in contributions to follow our AI Policy.

If your contribution does not follow the policy, it will be closed.

Setup

Rust (and a C compiler) are required to build uv.

On Ubuntu and other Debian-based distributions, you can install a C compiler with:

sudo apt install build-essential

On Fedora-based distributions, you can install a C compiler with:

sudo dnf install gcc

On Windows, NASM is required for building the TLS backend (aws-lc-sys). If it is not present, a prebuilt blob provided by aws-lc-sys will be used instead. WinGet can be used to install NASM:

winget install NASM.NASM

After installation, add C:\Program Files\NASM to your PATH. While the prebuilt blob will not be used when NASM is found, you can guarantee this behavior by setting AWS_LC_SYS_PREBUILT_NASM=0.

Testing

For running tests, we recommend nextest.

To run a specific test by name:

cargo nextest run -E 'test(test_name)'

To run all tests and accept snapshot changes:

cargo insta test --accept --test-runner nextest

To update snapshots for a specific test:

cargo insta test --accept --test-runner nextest -- <test_name>

Python

Testing uv requires multiple specific Python versions; they can be installed with:

cargo run python install

The storage directory can be configured with UV_PYTHON_INSTALL_DIR. (It must be an absolute path.)

Snapshot testing

uv uses insta for snapshot testing. It's recommended (but not necessary) to use cargo-insta for a better snapshot review experience. See the installation guide for more information.

In tests, you can use uv_snapshot! macro to simplify creating snapshots for uv commands. For example:

#[test]
fn test_add() {
    let context = TestContext::new("3.12");
    uv_snapshot!(context.filters(), context.add().arg("requests"), @"");
}

To run and review a specific snapshot test:

cargo test --package <package> --test <test> -- <test_name> -- --exact
cargo insta review

A script is available to update the snapshots based on results in CI. This is useful for updating snapshots without re-running the test suite and for updating platform-specific snapshots.

./scripts/apply-ci-snapshots.sh

Git and Git LFS

A subset of uv tests require both Git and Git LFS to execute properly.

These tests can be disabled by turning off either git or git-lfs uv features.

Local testing

You can invoke your development version of uv with cargo run -- <args>. For example:

cargo run -- venv
cargo run -- pip install requests

Formatting

# Rust
cargo fmt --all

# Python
uvx ruff format .

# Markdown, YAML, and other files (requires Node.js)
npx [email protected] --write .
# or in Docker
docker run --rm -v .:/src/ -w /src/ node:alpine npx [email protected] --write .

Linting

Linting requires shellcheck and cargo-shear to be installed separately.

# Rust
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings

# Python
uvx ruff check .

# Python type checking
uvx ty check python/uv

# Shell scripts
shellcheck <script>

# Spell checking
uvx typos

# Unused Rust dependencies
cargo shear

Compiling for Windows from Unix

To run clippy for a Windows target from Linux or macOS, you can use cargo-xwin:

# Install cargo-xwin
cargo install cargo-xwin --locked

# Add the Windows target
rustup target add x86_64-pc-windows-msvc

# Run clippy for Windows
cargo xwin clippy --workspace --all-targets --all-features --locked -- -D warnings

Crate structure

Rust does not allow circular dependencies between crates. To visualize the crate hierarchy, install cargo-depgraph and graphviz, then run:

cargo depgraph --dedup-transitive-deps --workspace-only | dot -Tpng > graph.png

Running inside a Docker container

Source distributions can run arbitrary code on build and can make unwanted modifications to your system ("Someone's Been Messing With My Subnormals!" on Blogspot, "nvidia-pyindex" on PyPI), which can even occur when just resolving requirements. To prevent this, there's a Docker container you can run commands in:

$ docker build -t uv-builder -f crates/uv-dev/builder.dockerfile --load .
# Build for musl to avoid glibc errors, might not be required with your OS version
cargo build --target x86_64-unknown-linux-musl --profile profiling
docker run --rm -it -v $(pwd):/app uv-builder /app/target/x86_64-unknown-linux-musl/profiling/uv-dev resolve-many --cache-dir /app/cache-docker /app/scripts/popular_packages/pypi_10k_most_dependents.txt

We recommend using this container if you don't trust the dependency tree of the package(s) you are trying to resolve or install.

Profiling and Benchmarking

Please refer to Ruff's Profiling Guide, it applies to uv, too.

We provide diverse sets of requirements for testing and benchmarking the resolver in test/requirements and for the installer in test/requirements/compiled.

You can use scripts/benchmark to benchmark predefined workloads between uv versions and with other tools, e.g., from the scripts/benchmark directory:

uv run resolver \
    --uv-pip \
    --poetry \
    --benchmark \
    resolve-cold \
    ../test/requirements/trio.in

Analyzing concurrency

You can use tracing-durations-export to visualize parallel requests and find any spots where uv is CPU-bound. Example usage, with uv and uv-dev respectively:

RUST_LOG=uv=info TRACING_DURATIONS_FILE=target/traces/jupyter.ndjson cargo run --features tracing-durations-export --profile profiling -- pip compile test/requirements/jupyter.in

RUST_LOG=uv=info TRACING_DURATIONS_FILE=target/traces/jupyter.ndjson cargo run --features tracing-durations-export --bin uv-dev --profile profiling -- resolve jupyter

Trace-level logging

You can enable trace level logging using the RUST_LOG environment variable, i.e.

RUST_LOG=trace uv

Documentation

To preview any changes to the documentation locally:

  1. Install the Rust toolchain.

  2. Run cargo dev generate-all, to update any auto-generated documentation.

  3. Run the development server with:

uv run --only-group docs mkdocs serve -f mkdocs.yml

The documentation should then be available locally at http://127.0.0.1:8000/uv/.

Documentation is deployed automatically on release by publishing to the Astral documentation repository, which itself deploys via Cloudflare Pages.

After making changes to the documentation, format the markdown files using Prettier.

Development code signing on macOS

Code signing can only be performed by Astral team members.

Code signing on macOS can improve developer experience when running tests, e.g., when running tests that access the macOS keychain, a signed binary can be approved once but an unsigned binary will need to be approved on each re-compile.

Acquiring a development certificate

  1. Generate a request for the certificate
  2. Create a certificate in the Apple Developer portal
  3. Download and install the certificate to your login keychain
security import ~/Downloads/mac_development.cer -k ~/Library/Keychains/login.keychain-db
  1. Identify your code signing identity
security find-identity -v -p codesigning
  1. If the above fails to find your identity, install the intermediate certificates
curl -sLO "https://www.apple.com/certificateauthority/AppleWWDRCAG3.cer"
security import AppleWWDRCAG3.cer -k ~/Library/Keychains/login.keychain-db
rm AppleWWDRCAG3.cer
  1. Set UV_TEST_CODESIGN_IDENTITY
export UV_TEST_CODESIGN_IDENTITY="Mac Developer: Your Name (TEAM_ID)"

Note UV_TEST_CODESIGN_IDENTITY is only supported via nextest.

Releases

Releases can only be performed by Astral team members.

Changelog entries and version bumps are automated. First, run:

./scripts/release.sh

If release preparation detects a new workspace crate, add it to astral-sh/crates-policies.

Then, editorialize the CHANGELOG.md file to ensure entries are consistently styled.

Then, open a pull request, e.g., Bump version to ....

Binary builds will automatically be tested for the release.

After merging the pull request, run the release workflow with the version tag. Do not include a leading v. The release will automatically be created on GitHub after everything else publishes.