Buck2

This repo contains the code for the Buck2 build system - the successor to the original Buck build system.

• To understand why Buck2 might be interesting, see this explainer or our introductory blog post.
• For our user-facing documentation see https://buck2.build/.

We're keen for you to give Buck2 a go and let us know any problems you run into.

Getting started

Buck2 is written in Rust, which requires rustup to compile.

You can either build buck2 from a clone of the Buck2 repo:

git clone https://github.com/facebook/buck2.git
cd buck2/
cargo install --path=app/buck2

Or alternatively install it directly from GitHub:

rustup install nightly-2023-01-24
cargo +nightly-2023-01-24 install --git https://github.com/facebook/buck2.git buck2

Build uses prebuilt protoc binary from protoc-bin-vendored crate. If these binaries to do not work on your machine (for example, when building for NixOS), path to protoc binary and protobuf include path can be specified via BUCK2_BUILD_PROTOC and BUCK2_BUILD_PROTOC_INCLUDE environment variables.

To build a project with buck2, go to the getting started guide.

Terminology conventions

Frequently used terms and their definitions can be found in the glossary page.

Coding conventions

Beyond the obvious (well-tested, easy to read) we prefer guidelines that are automatically enforced, e.g. through rust fmt, Clippy or the custom linter we have written. Some rules:

• Use the utilities from Gazebo where they are useful, in particular, dupe.
• Prefer to_owned to convert &str to String.
• Qualify anyhow::Result rather than use anyhow::Result.
• Most errors should be returned as anyhow::Result. Inspecting errors outside tests and the top-level error handler is strongly discouraged.
• Most errors should be constructed with thiserror deriving enum values, not raw anyhow!.
• We use the derivative library to derive the PartialEq and Hash traits when some fields should be ignored.
• Prefer use crate::foo::bar over use super::bar or use crate::foo::*, apart from test modules which often have use super::* at the top.
• Modules should either have submodules or types/functions/constants, but not both.
• Prefer anyhow::Error for checking internal invariants that are maintained between multiple files, while panic!/unreachable! are reasonable if the invariant is file-local.

Error messages

• Names (of variables, targets, files, etc) should be quoted with backticks, e.g. Variable `x` not defined.
• Lists should use square brackets, e.g. Available targets: [`aa`, `bb`].
• Error messages should start with an upper case letter. Error messages should not end with a period.

License

Buck2 is both MIT and Apache License, Version 2.0 licensed, as found in the LICENSE-MIT and LICENSE-APACHE files.