monkeyc-fmt is a syntax-preserving formatter for Garmin Monkey C. It parses source with Tree-sitter, changes whitespace between syntax tokens, and verifies that the formatted result has an equivalent syntax tree before returning it.

Comments, literal contents, parentheses, and punctuation are preserved. The Garmin Connect IQ SDK is not required.

Building requires the stable Rust toolchain and a native C compiler/toolchain for the Tree-sitter parser.

Install from crates.io:

cargo install --locked monkeyc-fmt

Alternatively, clone and install from source (requires Git):

git clone https://github.com/DuckSoft/monkeyc-fmt.git
cd monkeyc-fmt
cargo install --locked --path .

To build without installing:

cargo build --locked --release
./target/release/monkeyc-fmt --help

With no file, or with -, monkeyc-fmt reads standard input and writes formatted source to standard output:

$ printf 'var x=1;' | monkeyc-fmt
var x = 1;

A single file is also formatted to standard output without changing the file:

monkeyc-fmt source/App.mc

Format one or more files in place with --write (or -w):

monkeyc-fmt --write source/App.mc source/View.mc

Check files without changing them, for example in CI:

monkeyc-fmt --check source/*.mc

--check prints <path>: needs formatting to standard error for each file that would change.

Plain standard-output mode accepts exactly one input. Multiple inputs require --check or --write; standard input cannot be combined with other inputs, and --write rejects standard input.

• Only whitespace between syntax tokens is changed; token text and syntax are retained.
• The result is parsed again and compared with the original syntax tree. Unsafe output is refused.
• Invalid syntax and invalid UTF-8 are rejected rather than partially formatted.
• Output uses LF between tokens and one final LF for nonempty input. Empty or whitespace-only input produces empty output. Line endings inside comments and literals are untouched.
• Line width is a soft target: literals, comments, and other unsplittable tokens are not rewritten merely to meet it.
• Syntax nested beyond 256 levels is rejected to avoid stack exhaustion.
• In-place writes preserve file permissions, replace files atomically, reject symbolic links and non-regular files, and refuse to overwrite a file that changed while it was being formatted.

The checked-in toolchain configuration uses stable Rust with rustfmt and Clippy. Run the same checks as CI:

cargo fmt --all --check
cargo clippy --locked --all-targets -- -D warnings
cargo test --locked
cargo build --locked --release

CI runs these checks on Linux, macOS, and Windows.

This project is released into the public domain under The Unlicense.