Rustfmt

Rustfmt is a tool for formatting Rust code according to style guidelines. By default, Rustfmt uses a style which conforms to the Rust style guide that has been formalized through the style RFC process. A complete list of all configuration options can be found in the Rustfmt GitHub Pages.

Setup

Formatting your Rust targets' source code requires no setup outside of loading rules_rust in your workspace. Simply run bazel run @rules_rust//:rustfmt to format source code.

In addition to this formatter, a simple check can be performed using the rustfmt_aspect aspect by running:

bazel build --aspects=@rules_rust//rust:defs.bzl%rustfmt_aspect --output_groups=rustfmt_checks

Add the following to a .bazelrc file to enable this check during the build phase:

build --aspects=@rules_rust//rust:defs.bzl%rustfmt_aspect
build --output_groups=+rustfmt_checks

It's recommended to only enable this aspect in your CI environment so formatting issues do not impact users' ability to rapidly iterate on changes.

The rustfmt_aspect also uses a --@rules_rust//rust/settings:rustfmt.toml setting which determines the configuration file used by the formatter (@rules_rust//tools/rustfmt) and the aspect. This flag can be added to your .bazelrc file to ensure a consistent config file is used whenever rustfmt is run:

build --@rules_rust//rust/settings:rustfmt.toml=//:rustfmt.toml

Rules

• rustfmt_aspect — Aspect that runs rustfmt --check on every Rust target in the build. Attach in .bazelrc (as shown in Setup) to gate CI on formatting.
• rustfmt_test — Test rule that reports rustfmt findings as a test failure for a specific target.