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

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Usage

leo fmt [OPTIONS]

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Options

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--check
boolean
Check if files are formatted without making changes. Exit with code 1 if any files need formatting.
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--path
string
Specific file or directory to format. Defaults to current directory.

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Examples

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Format all files in project

leo fmt

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Check formatting without changes

leo fmt --check
This is useful in CI/CD pipelines: 
# In CI script
leo fmt --check || exit 1

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Format specific file

leo fmt --path src/main.leo

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Format specific directory

leo fmt --path src/

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Formatting Rules

Leo follows these formatting conventions:

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Indentation

  • Use 4 spaces for indentation
  • No tabs

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Line Length

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

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Spacing

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

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

// No trailing whitespace

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Function Declarations

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

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Imports

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

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Integration

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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

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VS Code

Configure VS Code to format on save by adding to .vscode/settings.json: 
{
  "leo.formatOnSave": true
}

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CI/CD Integration

Add formatting check to your CI pipeline: 
# GitHub Actions example
- name: Check formatting
  run: leo fmt --check
  • Build - Compile your formatted code
  • Test - Run tests on formatted code

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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.

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Troubleshooting

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Format check fails in CI

If leo fmt --check fails in CI, run locally: 
leo fmt
git add .
git commit -m "Format code"

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Syntax errors prevent formatting

Fix syntax errors before formatting: 
leo build  # Check for syntax errors
leo fmt    # Format after fixing errors