Formatter

Configuration related to the behavior of the Forge formatter. Each of these keys live under the [fmt] section.

single_line_statement_blocks

This allows configuring the style of statement blocks independently of the line length.

The single_line_statement_blocks configuration option in Foundry controls whether statement blocks (code blocks enclosed in { }) will be formatted to a single line or multiple lines.

It has three possible values:

  • "single" - Statement blocks will be formatted to a single line if possible.
  • "multi" - Statement blocks will always be formatted to multiple lines.
  • "preserve" - Keep the existing single/multi line formatting of statement blocks.

For example, with "single":

if (true) { return true; }

With "multi":

if (true) {
  return true;
}

And with "preserve", it will keep the original formatting of the code.

multiline_func_header

This allows configuring the formatting of long function headers.

  • Type: string
  • Default: attributes_first
  • Environment: FOUNDRY_FMT_MULTILINE_FUNC_HEADER or DAPP_FMT_MULTILINE_FUNC_HEADER

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.

Style of multiline function header in case it doesn’t fit in one line. Valid possible values:

  • "attributes_first" - (default) Write function attributes multiline first
  • "params_first" - Break the function header into multiple lines, with each parameter on its own line. The function name stays on the first line.
  • "all" - If function parameters or attributes are multiline, multiline everything

Style of multiline function header in case it doesn’t fit in one line. Valid values are:

For example, with "params_first":

function myFunction(
    uint256 param1, 
    uint256 param2,
    uint256 param3
) public returns (uint256) {
  // ...
}

And with "all":

function myFunction(
    uint256 param1,
    uint256 param2, 
    uint256 param3
) 
    public 
    returns (uint256) 
{
  // ...  
}

sort_imports

helps organize imports and makes it easier to find specific imports quickly.

The sort_imports configuration option in Foundry controls whether import statements are sorted alphabetically within their import groups.

From the code snippets provided:

  • In fmt.rs, sort_imports is a configuration option that can be set to true or false.
  • In formatter.rs, the sort_imports() method is called to sort import statements alphabetically if sort_imports is enabled.
  • It finds import groups separated by blank lines in the source code.
  • Then sorts the import statements within each group alphabetically.

So in summary, enabling sort_imports will reorder solidity import statements alphabetically within their section groups, while preserving the relative ordering of the groups.

contract_new_lines

Controls the addition of blank lines before and after contract definitions.

The contract_new_lines configuration option in Foundry controls whether empty lines are added before and after contract definitions.

When enabled (contract_new_lines = true):

  • An empty line will be added before the start of a contract definition.
  • An empty line will also be added after the end of a contract definition.

For example, with contract_new_lines enabled:

// Empty line before contract contract MyContract { // ... } // Empty line after contract

This helps visually separate contract definitions and improve readability.

When disabled (contract_new_lines = false), empty lines will not be added around contracts.

So in summary, the contract_new_lines option controls the addition of blank lines before and after contract definitions.

override_spacing

The override_spacing configuration option in Foundry controls whether a space is printed between the override keyword and the parent contracts when overriding a function or modifier.

When override_spacing is enabled:

  • A space will be added after the override keyword.

For example:

contract Child is Parent {
  function foo() override (Parent) public { }
}

When disabled, there will be no space between override and the parent contracts:

contract Child is Parent {
  function foo() override(Parent) public { } 
}

Enables configuring the styling of override declarations.

  • override_spacing = true - Print a space after override
  • override_spacing = false - No space after override

line_length

  • Type: number
  • Default: 120
  • Environment: FOUNDRY_FMT_LINE_LENGTH or DAPP_FMT_LINE_LENGTH

Maximum line length where formatter will try to wrap the line.

tab_width

  • Type: number
  • Default: 4
  • Environment: FOUNDRY_FMT_TAB_WIDTH or DAPP_FMT_TAB_WIDTH

Number of spaces per indentation level.

bracket_spacing

  • Type: bool
  • Default: false
  • Environment: FOUNDRY_FMT_BRACKET_SPACING or DAPP_FMT_BRACKET_SPACING

Whether or not to print spaces between brackets.

int_types

  • Type: string
  • Default: long
  • Environment: FOUNDRY_FMT_INT_TYPES or DAPP_FMT_INT_TYPES

Style of uint/int256 types. Valid values are:

  • long (default): Use the explicit uint256 or int256
  • short: Use the implicit uint or int
  • preserve: Use the type defined in the source code

quote_style

  • Type: string
  • Default: double
  • Environment: FOUNDRY_FMT_QUOTE_STYLE or DAPP_FMT_QUOTE_STYLE

Defines the quotation mark style. Valid values are:

  • double (default): Use double quotes where possible (")
  • single: Use single quotes where possible (')
  • preserve: Use quotation mark defined in the source code

number_underscore

  • Type: string
  • Default: preserve
  • Environment: FOUNDRY_FMT_NUMBER_UNDERSCORE or DAPP_FMT_NUMBER_UNDERSCORE

Style of underscores in number literals. Valid values are:

  • preserve (default): Use the underscores defined in the source code
  • thousands: Add an underscore every thousand, if greater than 9999. i.e. 1000 is formatted as 1000 and 10000 as 10_000
  • remove: Remove all underscores

hex_underscore

  • Type: string
  • Default: remove
  • Environment: FOUNDRY_FMT_HEX_UNDERSCORE or DAPP_FMT_HEX_UNDERSCORE

Style of underscores in bytes literals. Valid values are:

  • preserve: Use the underscores defined in the source code
  • remove (default): Remove all underscores
  • bytes: Add underscore as separator between byte boundaries. i.e. hex"deadbeef" is formatted as hex"de_ad_be_ef"

wrap_comments

  • Type: bool
  • Default: false
  • Environment: FOUNDRY_FMT_WRAP_COMMENTS or DAPP_FMT_WRAP_COMMENTS

Whether or not to wrap comments on line_length reached.

ignore

  • Type: array of strings (patterns)
  • Default: []
  • Environment: FOUNDRY_FMT_IGNORE or DAPP_FMT_IGNORE

List of files to ignore when formatting. This is a comma separated list of glob patterns.