yact

Yet another commit transformer-- but this one will finally help you truly forget about formatting!

yact is a tool that applies code formatters / prettifiers to your staged changes, seamlessly updating what you commit. Additionally, it works well when staging only some changes within a file-- it merges the formatting changes back into your worktree (accepting the worktree version in case of a conflict). It's like another programmer cleaning up your commits behind the scenes!

yact is designed to avoid the following issues that plague other popular auto-formatters / auto-formatting strategies:

1. Putting formatting changes in your worktree, aborting the commit, and forcing you to add back the formatting updates to whatever you staged. This is just annoying.
2. Not playing nice in cases when some changes are staged and some are unstaged and still in progress. Some tools result in borkage; others make you git add -p twice, which is again, just annoying.
3. Format on write can sometimes be jarring. For example, when writing a new function and then saving, the function will be reduced to a minimal form (ex. int main(){}).

For more information on how yact works, see this page.

Requirements and installation

1. Install Rust
2. cargo install yact
3. Set up desired code formatters: yact does not manage formatting tools. This entails that any desired external formatters must be installed and on the system path (or configured to be run from the workspace such as in the case of a virtual environment).

Usage (on a per-repository basis)

1. Create a config file named yactrc.toml in the workspace root. The docs/config_samples folder contains example config files that will apply to most people. Note that the configuration file is dependent on what languages and formatters your team prefers, so these may require modification.

• Rust sample
• C and C++ sample
• Web development sample
• Python sample
• Go sample

For a full list of configuration options, see this page.

2. Update your pre-commit git hook to run yact. In the simplest case (where no pre-commit hooks have been configured yet), run

yact init

This simply symlinks or hardlinks the yact executable into [repository root]/.git/hooks/pre-commit. If you already have pre-commit scripts set up that you'd like to keep, add yact to your script manually. Due to fallability of performing such an update automatically, these cases are left up to the user.

The configuration is now complete. Committed changes will be formatted transparently.

Transformers

yact defines a transformer as any process that applies some sort of formatting to a file. yact includes builtin transformers (written in native Rust) and transformers that invoke another process.

The standard interface for transformers that are a separate process are a command that reads a source file in from stdin and writes the formatter version to stdout, returning a nonzero exit code if the operation failed.

yact has the following builtin transformers:

• TrailingWhitespace: trims trailing whitespace and ensures the source file ends in a newline.

Additionally, yact has options for the following popular transformers (simply providing the correct command-line arguments to them):

• Rustfmt
• ClangFormat
• DenoFmt
• Prettier
• RuffFormat
• Gofmt

Finally, yact provides a catch-all System transformer where command, env, and args can be configured. Example below.

[[items]]
glob = "**/*.rs"
transformers = [ { External = { System = { command = "rustfmt", env = {}, args = ["--emit", "stdout"] }}}]

For a full list of configuration options, see this page.

Considerations

yact will never bork your git history. However, yact will take liberty in modifying your working tree as it sees fit. This is done in a fairly safe manner, merging formatting changes back into your worktree but keeping the worktree's version in case of conflicts.