What is rustfmt?
Rustfmt is a code formatting tool for Rust that helps ensure your code adheres to the community-driven coding standards and style guidelines. It automatically aligns and organizes code, focusing on spacing, indentations, and line lengths.
Rustfmt primarily targets .rs files, which are the source files for Rust programs.
Installing rustfmt
With Trunk Check, you can automatically install and configure rustfmt along with any relevant linters in a few straightforward steps. Here's how:
First, if you haven't already installed Trunk CLI, you can do so with the command below:
1curl https://get.trunk.io -fsSL | bash
Next, you can initialize Trunk from the root of your git repository:
1trunk init
This command will scan your repository and create a .trunk/trunk.yaml file that enables all linters, formatters, and security analyzers, recommended by Trunk Check. This includes rustfmt if applicable to your project.
To see all available linters Trunk Check installed, simply run:
1trunk check list
If you find rustfmt is not automatically enabled, you can do so by running:
1trunk check enable rustfmt
Alternatively, to disable rustfmt run the command below. To disable other tooling applied by Trunk Check, simply replace rustfmt with the respective tool you're looking to disable.
1trunk check disable rustfmt
For more details on Trunk Check setup, see here.
Configuring rustfmt
Most linters provide some mechanism to tweak their configuration, e.g. .eslintrc or Cargo.toml. Trunk is aware of all the ways individual tools are configured and supports them. This means linters you've already configured will continue to work exactly the same, just now supercharged by Trunk Check.
Like many formatters and linters with Trunk, rustfmt works out of the box, so there's no need to set up a custom configuration. However, rustfmt supports optional configuration files, such as .rustfmt.toml, allowing you to tailor formatting rules to your specific project needs. You can learn more about rustfmt and its config in our docs.
If you're interested in other tooling outside of rustfmt, check out our open-source repository to see how we define and support 90+ linters.
Running rustfmt
To check your code with rustfmt, run the command below. This command executes rustfmt along with any other formatters and linters Trunk Check has enabled on files you've modified. Since Trunk is git-aware, it knows what you've changed, and by adding batched execution and caching, you end up with a much faster and smoother way to run rustfmt and other tools.
1trunk check
If you prefer to check files you've modified with rustfmt only, run the following:
1trunk check --filter=rustfmt
Although we'd recommend against it depending on the size of your repository, you can check all files with rustfmt by running the command below.
1trunk check --all --filter=rustfmt
In most scenarios, you'll want to execute against modified files. Since Trunk is git-aware, it knows what you've changed, and by adding batched execution and caching, you end up with a much faster and smoother way to run rustfmt and other tools.
Updating Trunk Check & rustfmt
To upgrade the Trunk CLI along with all plugins and linters in your trunk.yaml simply run:
1trunk upgrade
We highly recommend running on the latest validated versions of tools as updates will frequently include important security fixes and additional valuable checks. Trunk only auto-suggests linter upgrades to versions that we have tested and support, so you may see a slight lag time when a new linter version is released.
Upgrade will also recommend new tools that have become applicable since the last time your repository was scanned. This can be a result of using new technologies in your repository or Trunk itself adding support for more tools. If you don't like a particular recommendation, you can always run trunk check disable <linter> to teach trunk not to recommend it.
Recommended Formatters to Pair with rustfmt
While rustfmt handles code formatting, pairing it with Clippy—Rust’s official linter—can significantly enhance your code quality. Clippy is designed to catch common mistakes and offer suggestions to improve your Rust code, making it the perfect companion to rustfmt. By using both tools, you'll ensure that your Rust code is not only well-formatted but also adheres to best practices.