leo fmt

Format Leo source files

Automatically format Leo source files according to the official Leo style guide. This command ensures consistent code formatting across your project.

Usage

leo fmt [OPTIONS]

Options

--check · boolean

Check if files are formatted without making changes. Exit with code 1 if any files need formatting.

--path · string

Specific file or directory to format. Defaults to current directory.

Examples

Format all files in project

leo fmt

Check formatting without changes

leo fmt --check

This is useful in CI/CD pipelines:

# In CI script
leo fmt --check || exit 1

Format specific file

leo fmt --path src/main.leo

Format specific directory

leo fmt --path src/

Formatting Rules

Leo follows these formatting conventions:

Indentation

• Use 4 spaces for indentation
• No tabs

Line Length

• Maximum 120 characters per line
• Break long lines at logical points

Spacing

// Correct spacing around operators
let sum: u32 = a + b;

// Spacing in function calls
let result: u32 = compute(x, y, z);

// No trailing whitespace

Function Declarations

// Properly formatted function
fn transfer(
    sender: address,
    receiver: address,
    amount: u64
) -> bool {
    return true;
}

Imports

// Group imports at the top
import token.aleo;
import utilities.aleo;

Integration

Pre-commit Hook

Add to .git/hooks/pre-commit:

#!/bin/bash
leo fmt --check
if [ $? -ne 0 ]; then
    echo "Code is not formatted. Run 'leo fmt' to format."
    exit 1
fi

VS Code

Configure VS Code to format on save by adding to .vscode/settings.json:

{
  "leo.formatOnSave": true
}

CI/CD Integration

Add formatting check to your CI pipeline:

# GitHub Actions example
- name: Check formatting
  run: leo fmt --check

Related Commands

• Build - Compile your formatted code
• Test - Run tests on formatted code

Best Practices

Run leo fmt before committing code to maintain consistent style across the team.

The formatter preserves comments and applies minimal changes to maintain code readability.

Troubleshooting

Format check fails in CI

If leo fmt --check fails in CI, run locally:

leo fmt
git add .
git commit -m "Format code"

Syntax errors prevent formatting

Fix syntax errors before formatting:

leo build  # Check for syntax errors
leo fmt    # Format after fixing errors