How to use the command rustfmt (with examples)

The rustfmt command is a tool used for formatting Rust source code. It helps ensure that the code adheres to a consistent style and formatting guidelines. This can greatly improve code readability and maintainability.

Use case 1: Format a file, overwriting the original file in-place

Code:

rustfmt path/to/source.rs

Motivation: One common use case of rustfmt is to format a Rust source file and overwrite the original file in-place. This can be useful when you want to update the formatting of the file without creating a separate formatted copy.

Explanation: In this use case, the command rustfmt is followed by the path to the source file path/to/source.rs. This tells rustfmt to format the specified Rust source file.

Example output: If the source file path/to/source.rs was not formatted according to the Rust style guidelines, rustfmt will reformat the file and overwrite the original file in-place. There will be no output displayed in the console if the formatting is successful.

Use case 2: Check a file for formatting and display any changes on the console

Code:

rustfmt --check path/to/source.rs

Motivation: Another use case of rustfmt is to check a Rust source file for formatting issues without modifying the file. This can be helpful for quickly identifying any formatting issues in the codebase.

Explanation: In this use case, the command rustfmt is followed by the --check option and the path to the source file path/to/source.rs. The --check option tells rustfmt to only check the file for formatting issues without making any modifications.

Example output: If the source file path/to/source.rs has any formatting issues, rustfmt will display the changes that need to be made to adhere to the Rust style guidelines. The output will show the line numbers and specific changes needed.

Use case 3: Backup any modified files before formatting

Code:

rustfmt --backup path/to/source.rs

Motivation: Sometimes, it’s important to back up the original file before modifying it. This can serve as a precautionary measure in case any issues arise from the formatting process.

Explanation: In this use case, the command rustfmt is followed by the --backup option and the path to the source file path/to/source.rs. The --backup option tells rustfmt to create a backup of the original file before making any modifications. The original file is renamed with a .bk extension.

Example output: If the source file path/to/source.rs was modified during the formatting process, rustfmt will create a backup of the original file with the .bk extension. The modified file will overwrite the original file, and there will be no output displayed in the console if the formatting is successful.

Conclusion:

In this article, we explored the various use cases of the rustfmt command. We learned how to format a file and overwrite the original file in-place, check a file for formatting issues without modifying it, and create backups of modified files before formatting. These use cases can greatly help in maintaining consistent formatting and improving the readability of Rust source code.