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Code Formatting

This repository uses treefmt with nixfmt and deadnix to maintain consistent formatting and clean code in Nix files.

Formatting Tools

nixfmt-rfc-style

  • Purpose: Formats Nix code according to RFC 166 style guidelines

  • What it does:

    • Standardizes indentation and spacing
    • Formats function calls and attribute sets consistently
    • Ensures consistent line breaks and alignment

deadnix

  • Purpose: Removes unused/dead code from Nix expressions

  • What it does:

    • Identifies unused variables and bindings
    • Removes unused function arguments
    • Cleans up dead code paths

Usage

Command Line

# Run treefmt and format all Nix files in the repository
nix fmt

In Development Shell

The formatter is available when you enter the development shell:

# Enter development shell
nix develop

# Format all nix files
treefmt

# Format specific files
treefmt file1.nix file2.nix

# Check formatting without making changes
treefmt --check

# Format with verbose output
treefmt --verbose

With direnv

If you're using direnv, the formatter is automatically available:

cd /path/to/project
treefmt

Configuration

The formatter configuration is defined with nix in nix/fmt.nix using treefmt-nix. See the treefmt-nix project documentation for the list of supported formatters and their configurations.

Integration with Pre-commit Hooks

The formatter is automatically run via pre-commit hooks (see pre-commit-hooks.md) to ensure all committed code is properly formatted.

Best Practices

1. Run Formatter Before Committing

nix fmt
git add .
git commit -m "your message"

2. Review Formatting Changes

Sometimes we want to first review formatting changes to ensure they're sensible:

# See what would be changed
treefmt --check --diff

Editor Integration

VS Code

Use the Nix IDE extension with treefmt support.