Forge formatter fails to format multi-line function header

[emilesean]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (206dab2 2024-12-16T00:25:12.607328550Z)

What command(s) is the bug in?

forge fmt

Operating System

Linux

Describe the bug

Forge formatter fails to format mulit-line function header

Steps to reproduce

1. Create a foundry project

forge init random
cd random

2. Create a IERC20.sol file with the following content.

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

interface IERC20 {
    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

3. Configure formatter add the following into foundry.toml file

[fmt]
single_line_statement_blocks = "multi"
multiline_func_header = 'params_first'

4. format the contents

forge fmt ./IERC20.sol

5. Output

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

interface IERC20 {
    function totalSupply() external view returns (uint256);

    function balanceOf(
        address account
    ) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

7. Expected Output

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

interface IERC20 {
    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(
        address recipient,
        uint256 amount
    ) external returns (bool);

    function allowance(
        address owner,
        address spender
    ) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

[grandizzy]

@emilesean per docs

The multiline_func_header configuration option in Foundry controls how function headers (the line containing the function name, parameters, return values etc.) are formatted when they exceed the max line length.

your sample doesn't exceed max line length (default to 120) hence no formatting, if you set line_length = 80 for example, they'll be formatted. Please reopen if still an issue, thank you!

[clouds56]

Now params_first would break function header into multiline with single parameter not matter its line width,
e.g. it would fmt

  function transfer(address to, uint value) external;
  function balanceOf(address account) external;

to

  function transfer(address to, uint256 value) external;
  function balanceOf(
    address account
  ) external;

Even if balanceOf is shorter than transfer.

Update

Use params_first_multi instead of params_first. See also #8762