rustfmttoml

rustfmttoml is an open‑source Rust library that provides automated formatting for TOML (Tom's Obvious Minimal Language) documents. The project was initiated in 2022 by a group of contributors interested in improving the readability and consistency of TOML configuration files through a tool that follows idiomatic Rust conventions. The crate is hosted on crates.io and its source code is maintained in a public repository on GitHub, where it is licensed under the MIT / Apache‑2.0 dual license.

The primary goal of rustfmttoml is to offer a deterministic, style‑aware formatter that can be integrated into Rust development workflows. It parses TOML input using the toml crate, constructs an abstract syntax tree, and then re‑emits the document according to a configurable set of formatting rules. These rules cover whitespace handling, indentation, ordering of table keys, and line wrapping for long strings. By default, the formatter adopts a 4‑space indentation style and aligns tables and arrays to improve visual hierarchy.

rustfmttoml can be invoked as a library function within Rust programs, or through a command‑line interface that reads files from standard input or from a specified path. The CLI supports options such as in‑place editing, diff output, and custom configuration files written in TOML. Integration with cargo‑fmt and other toolchains is straightforward, allowing developers to chain formatting steps for both Rust source code and associated TOML configuration files.

The crate has attracted contributions from the Rust community and is used in several projects that rely on consistent TOML formatting, including cargo‑metadata generators and CI pipelines. Ongoing development focuses on expanding rule configurability, improving error reporting, and maintaining compatibility with the latest TOML specifications.