Configuring Rustfmt

Rustfmt is designed to be very configurable. You can create a TOML file called rustfmt.toml or .rustfmt.toml, place it in the project or any other parent directory and it will apply the options in that file. If none of these directories contain such a file, both your home directory and a directory called rustfmt in your global config directory (e.g. .config/rustfmt/) are checked as well.

A possible content of rustfmt.toml or .rustfmt.toml might look like this:

indent_style = "Block"
reorder_imports = false

Each configuration option is either stable or unstable. Stable options can always be used, while unstable options are only available on a nightly toolchain and must be opted into. To enable unstable options, set unstable_features = true in rustfmt.toml or pass --unstable-features to rustfmt.

Configuration Options

Below you find a detailed visual guide on all the supported configuration options of rustfmt:

`array_width`

Maximum width of an array literal before falling back to vertical formatting.

Default value: 60
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for array_width will take precedence.

`attr_fn_like_width`

Maximum width of the args of a function-like attributes before falling back to vertical formatting.

Default value: 70
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for attr_fn_like_width will take precedence.

`binop_separator`

Where to put a binary operator when a binary expression goes multiline.

Default value: "Front"
Possible values: "Front", "Back"
Stable: No (tracking issue: #3368)

`"Front"` (default):

fn main() {
    let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo
        || barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;

    let sum = 123456789012345678901234567890
        + 123456789012345678901234567890
        + 123456789012345678901234567890;

    let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        ..bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
}

`"Back"`:

fn main() {
    let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo ||
        barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;

    let sum = 123456789012345678901234567890 +
        123456789012345678901234567890 +
        123456789012345678901234567890;

    let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..
        bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
}

`blank_lines_lower_bound`

Minimum number of blank lines which must be put between items. If two items have fewer blank lines between them, additional blank lines are inserted.

Default value: 0
Possible values: unsigned integer
Stable: No (tracking issue: #3382)

Example

Original Code (rustfmt will not change it with the default value of 0):

#![rustfmt::skip]

fn foo() {
    println!("a");
}
fn bar() {
    println!("b");
    println!("c");
}

`1`

fn foo() {

    println!("a");
}

fn bar() {

    println!("b");

    println!("c");
}

`blank_lines_upper_bound`

Maximum number of blank lines which can be put between items. If more than this number of consecutive empty lines are found, they are trimmed down to match this integer.

Default value: 1
Possible values: any non-negative integer
Stable: No (tracking issue: #3381)

Example

Original Code:

#![rustfmt::skip]

fn foo() {
    println!("a");
}



fn bar() {
    println!("b");


    println!("c");
}

`1` (default):

fn foo() {
    println!("a");
}

fn bar() {
    println!("b");

    println!("c");
}

`2`:

fn foo() {
    println!("a");
}


fn bar() {
    println!("b");


    println!("c");
}

`brace_style`

Brace style for items

Default value: "SameLineWhere"
Possible values: "AlwaysNextLine", "PreferSameLine", "SameLineWhere"
Stable: No (tracking issue: #3376)

Functions

`"SameLineWhere"` (default):

fn lorem() {
    // body
}

fn lorem(ipsum: usize) {
    // body
}

fn lorem<T>(ipsum: T)
where
    T: Add + Sub + Mul + Div,
{
    // body
}

`"AlwaysNextLine"`:

fn lorem()
{
    // body
}

fn lorem(ipsum: usize)
{
    // body
}

fn lorem<T>(ipsum: T)
where
    T: Add + Sub + Mul + Div,
{
    // body
}

`"PreferSameLine"`:

fn lorem() {
    // body
}

fn lorem(ipsum: usize) {
    // body
}

fn lorem<T>(ipsum: T)
where
    T: Add + Sub + Mul + Div, {
    // body
}

Structs and enums

`"SameLineWhere"` (default):

struct Lorem {
    ipsum: bool,
}

struct Dolor<T>
where
    T: Eq,
{
    sit: T,
}

`"AlwaysNextLine"`:

struct Lorem
{
    ipsum: bool,
}

struct Dolor<T>
where
    T: Eq,
{
    sit: T,
}

`"PreferSameLine"`:

struct Lorem {
    ipsum: bool,
}

struct Dolor<T>
where
    T: Eq, {
    sit: T,
}

`chain_width`

Maximum width of a chain to fit on one line.

Default value: 60
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for chain_width will take precedence.

`color`

Whether to use colored output or not.

Default value: "Auto"
Possible values: “Auto”, “Always”, “Never”
Stable: No (tracking issue: #3385)

`combine_control_expr`

Combine control expressions with function calls.

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3369)

`true` (default):

fn example() {
    // If
    foo!(if x {
        foo();
    } else {
        bar();
    });

    // IfLet
    foo!(if let Some(..) = x {
        foo();
    } else {
        bar();
    });

    // While
    foo!(while x {
        foo();
        bar();
    });

    // WhileLet
    foo!(while let Some(..) = x {
        foo();
        bar();
    });

    // ForLoop
    foo!(for x in y {
        foo();
        bar();
    });

    // Loop
    foo!(loop {
        foo();
        bar();
    });
}

`false`:

fn example() {
    // If
    foo!(
        if x {
            foo();
        } else {
            bar();
        }
    );

    // IfLet
    foo!(
        if let Some(..) = x {
            foo();
        } else {
            bar();
        }
    );

    // While
    foo!(
        while x {
            foo();
            bar();
        }
    );

    // WhileLet
    foo!(
        while let Some(..) = x {
            foo();
            bar();
        }
    );

    // ForLoop
    foo!(
        for x in y {
            foo();
            bar();
        }
    );

    // Loop
    foo!(
        loop {
            foo();
            bar();
        }
    );
}

`comment_width`

Maximum length of comments. No effect unless wrap_comments = true.

Default value: 80
Possible values: any positive integer
Stable: No (tracking issue: #3349)

Note: A value of 0 results in wrap_comments being applied regardless of a line's width.

`80` (default; comments shorter than `comment_width`):

// Lorem ipsum dolor sit amet, consectetur adipiscing elit.

`60` (comments longer than `comment_width`):

// Lorem ipsum dolor sit amet,
// consectetur adipiscing elit.

`condense_wildcard_suffixes`

Replace strings of _ wildcards by a single .. in tuple patterns

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3384)

`false` (default):

fn main() {
    let (lorem, ipsum, _, _) = (1, 2, 3, 4);
    let (lorem, ipsum, ..) = (1, 2, 3, 4);
}

`true`:

fn main() {
    let (lorem, ipsum, ..) = (1, 2, 3, 4);
}

`control_brace_style`

Brace style for control flow constructs

Default value: "AlwaysSameLine"
Possible values: "AlwaysNextLine", "AlwaysSameLine", "ClosingNextLine"
Stable: No (tracking issue: #3377)

`"AlwaysSameLine"` (default):

fn main() {
    if lorem {
        println!("ipsum!");
    } else {
        println!("dolor!");
    }
}

`"AlwaysNextLine"`:

fn main() {
    if lorem
    {
        println!("ipsum!");
    }
    else
    {
        println!("dolor!");
    }
}

`"ClosingNextLine"`:

fn main() {
    if lorem {
        println!("ipsum!");
    }
    else {
        println!("dolor!");
    }
}

`disable_all_formatting`

Don't reformat anything.

Note that this option may be soft-deprecated in the future once the ignore option is stabilized. Nightly toolchain users are encouraged to use ignore instead when possible.

Default value: false
Possible values: true, false
Stable: Yes

`edition`

Specifies which edition is used by the parser.

Default value: "2015"
Possible values: "2015", "2018", "2021", "2024"
Stable: Yes

Rustfmt is able to pick up the edition used by reading the Cargo.toml file if executed through the Cargo's formatting tool cargo fmt. Otherwise, the edition needs to be specified in your config file:

edition = "2018"

`empty_item_single_line`

Put empty-body functions and impls on a single line

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3356)

`true` (default):

fn lorem() {}

impl Lorem {}

`false`:

fn lorem() {
}

impl Lorem {
}

`enum_discrim_align_threshold`

The maximum length of enum variant having discriminant, that gets vertically aligned with others. Variants without discriminants would be ignored for the purpose of alignment.

Note that this is not how much whitespace is inserted, but instead the longest variant name that doesn't get ignored when aligning.

Default value : 0
Possible values: any positive integer
Stable: No (tracking issue: #3372)

`0` (default):

enum Foo {
    A = 0,
    Bb = 1,
    RandomLongVariantGoesHere = 10,
    Ccc = 71,
}

enum Bar {
    VeryLongVariantNameHereA = 0,
    VeryLongVariantNameHereBb = 1,
    VeryLongVariantNameHereCcc = 2,
}

`20`:

enum Foo {
    A   = 0,
    Bb  = 1,
    RandomLongVariantGoesHere = 10,
    Ccc = 2,
}

enum Bar {
    VeryLongVariantNameHereA = 0,
    VeryLongVariantNameHereBb = 1,
    VeryLongVariantNameHereCcc = 2,
}

`error_on_line_overflow`

Error if Rustfmt is unable to get all lines within max_width, except for comments and string literals. If this happens, then it is a bug in Rustfmt. You might be able to work around the bug by refactoring your code to avoid long/complex expressions, usually by extracting a local variable or using a shorter name.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3391)

`error_on_unformatted`

Error if unable to get comments or string literals within max_width, or they are left with trailing whitespaces.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3392)

`fn_args_layout`

This option is deprecated and has been renamed to fn_params_layout to better communicate that it affects the layout of parameters in function signatures.

Default value: "Tall"
Possible values: "Compressed", "Tall", "Vertical"
Stable: Yes

`"Tall"` (default):

trait Lorem {
    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);

    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
        // body
    }

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    ) {
        // body
    }
}

`"Compressed"`:

trait Lorem {
    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);

    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
        // body
    }

    fn lorem(
        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
        adipiscing: Adipiscing, elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
        adipiscing: Adipiscing, elit: Elit,
    ) {
        // body
    }
}

`"Vertical"`:

trait Lorem {
    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
    ) {
        // body
    }

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    ) {
        // body
    }
}

`fn_call_width`

Maximum width of the args of a function call before falling back to vertical formatting.

Default value: 60
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for fn_call_width will take precedence.

`fn_params_layout`

Control the layout of parameters in function signatures.

Default value: "Tall"
Possible values: "Compressed", "Tall", "Vertical"
Stable: Yes

`"Tall"` (default):

trait Lorem {
    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);

    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
        // body
    }

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    ) {
        // body
    }
}

`"Compressed"`:

trait Lorem {
    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);

    fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
        // body
    }

    fn lorem(
        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
        adipiscing: Adipiscing, elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
        adipiscing: Adipiscing, elit: Elit,
    ) {
        // body
    }
}

`"Vertical"`:

trait Lorem {
    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
    ) {
        // body
    }

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    );

    fn lorem(
        ipsum: Ipsum,
        dolor: Dolor,
        sit: Sit,
        amet: Amet,
        consectetur: Consectetur,
        adipiscing: Adipiscing,
        elit: Elit,
    ) {
        // body
    }
}

`fn_single_line`

Put single-expression functions on a single line

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3358)

`false` (default):

fn lorem() -> usize {
    42
}

fn lorem() -> usize {
    let ipsum = 42;
    ipsum
}

`true`:

fn lorem() -> usize { 42 }

fn lorem() -> usize {
    let ipsum = 42;
    ipsum
}

`force_explicit_abi`

Always print the abi for extern items

Default value: true
Possible values: true, false
Stable: Yes

Note: Non-“C” ABIs are always printed. If false then “C” is removed.

`true` (default):

extern "C" {
    pub static lorem: c_int;
}

`false`:

extern {
    pub static lorem: c_int;
}

`force_multiline_blocks`

Force multiline closure and match arm bodies to be wrapped in a block

Default value: false
Possible values: false, true
Stable: No (tracking issue: #3374)

`false` (default):

fn main() {
    result.and_then(|maybe_value| match maybe_value {
        None => foo(),
        Some(value) => bar(),
    });

    match lorem {
        None => |ipsum| {
            println!("Hello World");
        },
        Some(dolor) => foo(),
    }
}

`true`:

fn main() {
    result.and_then(|maybe_value| {
        match maybe_value {
            None => foo(),
            Some(value) => bar(),
        }
    });

    match lorem {
        None => {
            |ipsum| {
                println!("Hello World");
            }
        }
        Some(dolor) => foo(),
    }
}

`format_code_in_doc_comments`

Format code snippet included in doc comments.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3348)

`false` (default):

/// Adds one to the number given.
///
/// # Examples
///
/// ```rust
/// let five=5;
///
/// assert_eq!(
///     6,
///     add_one(5)
/// );
/// # fn add_one(x: i32) -> i32 {
/// #     x + 1
/// # }
/// ```
fn add_one(x: i32) -> i32 {
    x + 1
}

`true`

/// Adds one to the number given.
///
/// # Examples
///
/// ```rust
/// let five = 5;
///
/// assert_eq!(6, add_one(5));
/// # fn add_one(x: i32) -> i32 {
/// #     x + 1
/// # }
/// ```
fn add_one(x: i32) -> i32 {
    x + 1
}

`doc_comment_code_block_width`

Max width for code snippets included in doc comments. Only used if format_code_in_doc_comments is true.

Default value: 100
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: No (tracking issue: #5359)

`format_generated_files`

Format generated files. A file is considered generated if any of the first several lines contain a @generated comment marker. The number of lines to check is configured by generated_marker_line_search_limit.

By default, generated files are reformatted, i. e. @generated marker is ignored. This option is currently ignored for stdin (@generated in stdin is ignored.)

Default value: true
Possible values: true, false
Stable: No (tracking issue: #5080)

`generated_marker_line_search_limit`

Number of lines to check for a @generated pragma header, starting from the top of the file. Setting this value to 0 will treat all files as non-generated. Whenformat_generated_files is true, this option has no effect.

Default value: 5
Possible values: any positive integer
Stable: No (tracking issue: #5080)

See also format_generated_files link here.

`format_macro_matchers`

Format the metavariable matching patterns in macros.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3354)

`false` (default):

macro_rules! foo {
    ($a: ident : $b: ty) => {
        $a(42): $b;
    };
    ($a: ident $b: ident $c: ident) => {
        $a = $b + $c;
    };
}

`true`:

macro_rules! foo {
    ($a:ident : $b:ty) => {
        $a(42): $b;
    };
    ($a:ident $b:ident $c:ident) => {
        $a = $b + $c;
    };
}

`format_macro_bodies`

Format the bodies of declarative macro definitions.

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3355)

`true` (default):

macro_rules! foo {
    ($a: ident : $b: ty) => {
        $a(42): $b;
    };
    ($a: ident $b: ident $c: ident) => {
        $a = $b + $c;
    };
}

`false`:

macro_rules! foo {
    ($a: ident : $b: ty) => { $a(42): $b; };
    ($a: ident $b: ident $c: ident) => { $a=$b+$c; };
}

`skip_macro_invocations`

Skip formatting the bodies of macro invocations with the following names.

rustfmt will not format any macro invocation for macros with names set in this list. Including the special value “*” will prevent any macro invocations from being formatted.

Note: This option does not have any impact on how rustfmt formats macro definitions.

Default value: []
Possible values: a list of macro name idents, ["name_0", "name_1", ..., "*"]
Stable: No (tracking issue: #5346)

`[]` (default):

rustfmt will follow its standard approach to formatting macro invocations.

No macro invocations will be skipped based on their name. More information about rustfmt's standard macro invocation formatting behavior can be found in #5437.

lorem!(
    const _: u8 = 0;
);

ipsum!(
    const _: u8 = 0;
);

`["lorem"]`:

The named macro invocations will be skipped.

lorem!(
        const _: u8 = 0;
);

ipsum!(
    const _: u8 = 0;
);

`["*"]`:

The special selector * will skip all macro invocations.

lorem!(
        const _: u8 = 0;
);

ipsum!(
        const _: u8 = 0;
);

`format_strings`

Format string literals where necessary

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3353)

`false` (default):

fn main() {
    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet consectetur adipiscing";
}

`true`:

fn main() {
    let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet \
                 consectetur adipiscing";
}

`hard_tabs`

Use tab characters for indentation, spaces for alignment

Default value: false
Possible values: true, false
Stable: Yes

`false` (default):

fn lorem() -> usize {
    42 // spaces before 42
}

`true`:

fn lorem() -> usize {
	42 // tabs before 42
}

`hex_literal_case`

Control the case of the letters in hexadecimal literal values

Default value: Preserve
Possible values: Preserve, Upper, Lower
Stable: No (tracking issue: #5081)

`hide_parse_errors`

This option is deprecated and has been renamed to show_parse_errors to avoid confusion around the double negative default of hide_parse_errors=false.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3390)

`show_parse_errors`

Show parse errors if the parser failed to parse files.

Default value: true
Possible values: true, false
Stable: No (tracking issue: #5977)

`ignore`

Skip formatting files and directories that match the specified pattern. The pattern format is the same as .gitignore. Be sure to use Unix/forwardslash / style paths. This path style will work on all platforms. Windows style paths with backslashes \ are not supported.

Default value: format every file
Possible values: See an example below
Stable: No (tracking issue: #3395)

Example

If you want to ignore specific files, put the following to your config file:

ignore = [
    "src/types.rs",
    "src/foo/bar.rs",
]

If you want to ignore every file under examples/, put the following to your config file:

ignore = [
    "examples",
]

If you want to ignore every file under the directory where you put your rustfmt.toml:

ignore = ["/"]

If you want to allow specific paths that would otherwise be ignored, prefix those paths with a !:

ignore = ["bar_dir/*", "!bar_dir/*/what.rs"]

In this case, all files under bar_dir will be ignored, except files like bar_dir/sub/what.rs or bar_dir/another/what.rs.

`imports_indent`

Indent style of imports

Default Value: "Block"
Possible values: "Block", "Visual"
Stable: No (tracking issue: #3360)

`"Block"` (default):

use foo::{
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
    zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
};

`"Visual"`:

use foo::{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
          zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz};

`imports_layout`

Item layout inside a imports block

Default value: “Mixed”
Possible values: “Horizontal”, “HorizontalVertical”, “Mixed”, “Vertical”
Stable: No (tracking issue: #3361)

`"Mixed"` (default):

use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};

use foo::{
    aaaaaaaaaaaaaaaaaa, bbbbbbbbbbbbbbbbbb, cccccccccccccccccc, dddddddddddddddddd,
    eeeeeeeeeeeeeeeeee, ffffffffffffffffff,
};

`"Horizontal"`:

Note: This option forces all imports onto one line and may exceed max_width.

use foo::{xxx, yyy, zzz};

use foo::{aaa, bbb, ccc, ddd, eee, fff};

`"HorizontalVertical"`:

use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};

use foo::{
    aaaaaaaaaaaaaaaaaa,
    bbbbbbbbbbbbbbbbbb,
    cccccccccccccccccc,
    dddddddddddddddddd,
    eeeeeeeeeeeeeeeeee,
    ffffffffffffffffff,
};

`"Vertical"`:

use foo::{
    xxx,
    yyy,
    zzz,
};

use foo::{
    aaa,
    bbb,
    ccc,
    ddd,
    eee,
    fff,
};

`indent_style`

Indent on expressions or items.

Default value: "Block"
Possible values: "Block", "Visual"
Stable: No (tracking issue: #3346)

Array

`"Block"` (default):

fn main() {
    let lorem = vec![
        "ipsum",
        "dolor",
        "sit",
        "amet",
        "consectetur",
        "adipiscing",
        "elit",
    ];
}

`"Visual"`:

fn main() {
    let lorem = vec!["ipsum",
                     "dolor",
                     "sit",
                     "amet",
                     "consectetur",
                     "adipiscing",
                     "elit"];
}

Control flow

`"Block"` (default):

fn main() {
    if lorem_ipsum
        && dolor_sit
        && amet_consectetur
        && lorem_sit
        && dolor_consectetur
        && amet_ipsum
        && lorem_consectetur
    {
        // ...
    }
}

`"Visual"`:

fn main() {
    if lorem_ipsum
       && dolor_sit
       && amet_consectetur
       && lorem_sit
       && dolor_consectetur
       && amet_ipsum
       && lorem_consectetur
    {
        // ...
    }
}

Function arguments

`"Block"` (default):

fn lorem() {}

fn lorem(ipsum: usize) {}

fn lorem(
    ipsum: usize,
    dolor: usize,
    sit: usize,
    amet: usize,
    consectetur: usize,
    adipiscing: usize,
    elit: usize,
) {
    // body
}

`"Visual"`:

fn lorem() {}

fn lorem(ipsum: usize) {}

fn lorem(ipsum: usize,
         dolor: usize,
         sit: usize,
         amet: usize,
         consectetur: usize,
         adipiscing: usize,
         elit: usize) {
    // body
}

Function calls

`"Block"` (default):

fn main() {
    lorem(
        "lorem",
        "ipsum",
        "dolor",
        "sit",
        "amet",
        "consectetur",
        "adipiscing",
        "elit",
    );
}

`"Visual"`:

fn main() {
    lorem("lorem",
          "ipsum",
          "dolor",
          "sit",
          "amet",
          "consectetur",
          "adipiscing",
          "elit");
}

Generics

`"Block"` (default):

fn lorem<
    Ipsum: Eq = usize,
    Dolor: Eq = usize,
    Sit: Eq = usize,
    Amet: Eq = usize,
    Adipiscing: Eq = usize,
    Consectetur: Eq = usize,
    Elit: Eq = usize,
>(
    ipsum: Ipsum,
    dolor: Dolor,
    sit: Sit,
    amet: Amet,
    adipiscing: Adipiscing,
    consectetur: Consectetur,
    elit: Elit,
) -> T {
    // body
}

`"Visual"`:

fn lorem<Ipsum: Eq = usize,
         Dolor: Eq = usize,
         Sit: Eq = usize,
         Amet: Eq = usize,
         Adipiscing: Eq = usize,
         Consectetur: Eq = usize,
         Elit: Eq = usize>(
    ipsum: Ipsum,
    dolor: Dolor,
    sit: Sit,
    amet: Amet,
    adipiscing: Adipiscing,
    consectetur: Consectetur,
    elit: Elit)
    -> T {
    // body
}

Struct

`"Block"` (default):

fn main() {
    let lorem = Lorem {
        ipsum: dolor,
        sit: amet,
    };
}

`"Visual"`:

fn main() {
    let lorem = Lorem { ipsum: dolor,
                        sit: amet };
}

Where predicates

`"Block"` (default):

fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
where
    Ipsum: Eq,
    Dolor: Eq,
    Sit: Eq,
    Amet: Eq,
{
    // body
}

`"Visual"`:

fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
    where Ipsum: Eq,
          Dolor: Eq,
          Sit: Eq,
          Amet: Eq
{
    // body
}

`inline_attribute_width`

Write an item and its attribute on the same line if their combined width is below a threshold

Default value: 0
Possible values: any positive integer
Stable: No (tracking issue: #3343)

Example

`0` (default):

#[cfg(feature = "alloc")]
use core::slice;

`50`:

#[cfg(feature = "alloc")] use core::slice;

`match_arm_blocks`

Controls whether arm bodies are wrapped in cases where the first line of the body cannot fit on the same line as the => operator.

The Style Guide requires that bodies are block wrapped by default if a line break is required after the =>, but this option can be used to disable that behavior to prevent wrapping arm bodies in that event, so long as the body contains neither multiple statements nor line comments.

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3373)

`true` (default):

fn main() {
    match lorem {
        ipsum => {
            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
        }
        dolor => println!("{}", sit),
        sit => foo(
            "foooooooooooooooooooooooo",
            "baaaaaaaaaaaaaaaaaaaaaaaarr",
            "baaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzz",
            "qqqqqqqqquuuuuuuuuuuuuuuuuuuuuuuuuuxxx",
        ),
    }
}

`false`:

fn main() {
    match lorem {
        lorem =>
            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
        ipsum => println!("{}", sit),
        sit => foo(
            "foooooooooooooooooooooooo",
            "baaaaaaaaaaaaaaaaaaaaaaaarr",
            "baaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzz",
            "qqqqqqqqquuuuuuuuuuuuuuuuuuuuuuuuuuxxx",
        ),
    }
}

`match_arm_leading_pipes`

Controls whether to include a leading pipe on match arms

Default value: Never
Possible values: Always, Never, Preserve
Stable: Yes

`Never` (default):

// Leading pipes are removed from this:
// fn foo() {
//     match foo {
//         | "foo" | "bar" => {}
//         | "baz"
//         | "something relatively long"
//         | "something really really really realllllllllllllly long" => println!("x"),
//         | "qux" => println!("y"),
//         _ => {}
//     }
// }

// Becomes
fn foo() {
    match foo {
        "foo" | "bar" => {}
        "baz"
        | "something relatively long"
        | "something really really really realllllllllllllly long" => println!("x"),
        "qux" => println!("y"),
        _ => {}
    }
}

`Always`:

// Leading pipes are emitted on all arms of this:
// fn foo() {
//     match foo {
//         "foo" | "bar" => {}
//         "baz"
//         | "something relatively long"
//         | "something really really really realllllllllllllly long" => println!("x"),
//         "qux" => println!("y"),
//         _ => {}
//     }
// }

// Becomes:
fn foo() {
    match foo {
        | "foo" | "bar" => {}
        | "baz"
        | "something relatively long"
        | "something really really really realllllllllllllly long" => println!("x"),
        | "qux" => println!("y"),
        | _ => {}
    }
}

`Preserve`:

fn foo() {
    match foo {
        | "foo" | "bar" => {}
        | "baz"
        | "something relatively long"
        | "something really really really realllllllllllllly long" => println!("x"),
        | "qux" => println!("y"),
        _ => {}
    }

    match baz {
        "qux" => {}
        "foo" | "bar" => {}
        _ => {}
    }
}

`match_block_trailing_comma`

Put a trailing comma after a block based match arm (non-block arms are not affected)

Default value: false
Possible values: true, false
Stable: Yes

`false` (default):

fn main() {
    match lorem {
        Lorem::Ipsum => {
            println!("ipsum");
        }
        Lorem::Dolor => println!("dolor"),
    }
}

`true`:

fn main() {
    match lorem {
        Lorem::Ipsum => {
            println!("ipsum");
        },
        Lorem::Dolor => println!("dolor"),
    }
}

`max_width`

Maximum width of each line

Default value: 100
Possible values: any positive integer
Stable: Yes

`merge_derives`

Merge multiple derives into a single one.

Default value: true
Possible values: true, false
Stable: Yes

`true` (default):

#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum Foo {}

`false`:

#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum Bar {}

#[derive(Eq, PartialEq)]
#[derive(Debug)]
#[derive(Copy, Clone)]
pub enum Foo {}

`imports_granularity`

Controls how imports are structured in use statements. Imports will be merged or split to the configured level of granularity.

Similar to other import related configuration options, this option operates within the bounds of user-defined groups of imports. See group_imports for more information on import groups.

Note that rustfmt will not modify the granularity of imports containing comments if doing so could potentially lose or misplace said comments.

Default value: Preserve
Possible values: Preserve, Crate, Module, Item, One
Stable: No (tracking issue: #4991)

`Preserve` (default):

Do not change the granularity of any imports and preserve the original structure written by the developer.

use foo::b;
use foo::b::{f, g};
use foo::{a, c, d::e};
use qux::{h, i};

`Crate`:

Merge imports from the same crate into a single use statement. Conversely, imports from different crates are split into separate statements.

use foo::{
    a, b,
    b::{f, g},
    c,
    d::e,
};
use qux::{h, i};

`Module`:

Merge imports from the same module into a single use statement. Conversely, imports from different modules are split into separate statements.

use foo::b::{f, g};
use foo::d::e;
use foo::{a, b, c};
use qux::{h, i};

`Item`:

Flatten imports so that each has its own use statement.

use foo::a;
use foo::b;
use foo::b::f;
use foo::b::g;
use foo::c;
use foo::d::e;
use qux::h;
use qux::i;

`One`:

Merge all imports into a single use statement as long as they have the same visibility.

pub use foo::{x, y};
use {
    bar::{
        a,
        b::{self, f, g},
        c,
        d::e,
    },
    qux::{h, i},
};

`merge_imports`

This option is deprecated. Use imports_granularity = "Crate" instead.

Default value: false
Possible values: true, false

`false` (default):

use foo::{a, c, d};
use foo::{b, g};
use foo::{e, f};

`true`:

use foo::{a, b, c, d, e, f, g};

`newline_style`

Unix or Windows line endings

Default value: "Auto"
Possible values: "Auto", "Native", "Unix", "Windows"
Stable: Yes

`Auto` (default):

The newline style is detected automatically on a per-file basis. Files with mixed line endings will be converted to the first detected line ending style.

`Native`

Line endings will be converted to \r\n on Windows and \n on all other platforms.

`Unix`

Line endings will be converted to \n.

`Windows`

Line endings will be converted to \r\n.

`normalize_comments`

Convert /* */ comments to // comments where possible

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3350)

`false` (default):

// Lorem ipsum:
fn dolor() -> usize {}

/* sit amet: */
fn adipiscing() -> usize {}

`true`:

// Lorem ipsum:
fn dolor() -> usize {}

// sit amet:
fn adipiscing() -> usize {}

`normalize_doc_attributes`

Convert #![doc] and #[doc] attributes to //! and /// doc comments.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3351)

`false` (default):

#![doc = "Example documentation"]

#[doc = "Example item documentation"]
pub enum Bar {}

/// Example item documentation
pub enum Foo {}

`true`:

//! Example documentation

/// Example item documentation
pub enum Foo {}

`overflow_delimited_expr`

When structs, slices, arrays, and block/array-like macros are used as the last argument in an expression list, allow them to overflow (like blocks/closures) instead of being indented on a new line.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3370)

`false` (default):

fn example() {
    foo(ctx, |param| {
        action();
        foo(param)
    });

    foo(
        ctx,
        Bar {
            x: value,
            y: value2,
        },
    );

    foo(
        ctx,
        &[
            MAROON_TOMATOES,
            PURPLE_POTATOES,
            ORGANE_ORANGES,
            GREEN_PEARS,
            RED_APPLES,
        ],
    );

    foo(
        ctx,
        vec![
            MAROON_TOMATOES,
            PURPLE_POTATOES,
            ORGANE_ORANGES,
            GREEN_PEARS,
            RED_APPLES,
        ],
    );
}

`true`:

fn example() {
    foo(ctx, |param| {
        action();
        foo(param)
    });

    foo(ctx, Bar {
        x: value,
        y: value2,
    });

    foo(ctx, &[
        MAROON_TOMATOES,
        PURPLE_POTATOES,
        ORGANE_ORANGES,
        GREEN_PEARS,
        RED_APPLES,
    ]);

    foo(ctx, vec![
        MAROON_TOMATOES,
        PURPLE_POTATOES,
        ORGANE_ORANGES,
        GREEN_PEARS,
        RED_APPLES,
    ]);
}

`remove_nested_parens`

Remove nested parens.

Default value: true,
Possible values: true, false
Stable: Yes

`true` (default):

fn main() {
    (foo());
}

`false`:

fn main() {
    (foo());

    ((((foo()))));
}

`reorder_impl_items`

Reorder impl items. type and const are put first, then macros and methods.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3363)

`false` (default)

struct Dummy;

impl Iterator for Dummy {
    fn next(&mut self) -> Option<Self::Item> {
        None
    }

    type Item = i32;
}

impl Iterator for Dummy {
    type Item = i32;

    fn next(&mut self) -> Option<Self::Item> {
        None
    }
}

`true`

struct Dummy;

impl Iterator for Dummy {
    type Item = i32;

    fn next(&mut self) -> Option<Self::Item> {
        None
    }
}

`reorder_imports`

Reorder import and extern crate statements alphabetically in groups (a group is separated by a newline).

Default value: true
Possible values: true, false
Stable: Yes

`true` (default):

use dolor;
use ipsum;
use lorem;
use sit;

`false`:

use lorem;
use ipsum;
use dolor;
use sit;

`group_imports`

Controls the strategy for how consecutive imports are grouped together.

Controls the strategy for grouping sets of consecutive imports. Imports may contain newlines between imports and still be grouped together as a single set, but other statements between imports will result in different grouping sets.

Default value: Preserve
Possible values: Preserve, StdExternalCrate, One
Stable: No (tracking issue: #5083)

Each set of imports (one or more use statements, optionally separated by newlines) will be formatted independently. Other statements such as mod ... or extern crate ... will cause imports to not be grouped together.

`Preserve` (default):

Preserve the source file's import groups.

use super::update::convert_publish_payload;
use chrono::Utc;

use alloc::alloc::Layout;
use juniper::{FieldError, FieldResult};
use uuid::Uuid;

use std::sync::Arc;

use broker::database::PooledConnection;

use super::schema::{Context, Payload};
use crate::models::Event;
use core::f32;

`StdExternalCrate`:

Discard existing import groups, and create three groups for:

std, core and alloc,
external crates,
self, super and crate imports.

use alloc::alloc::Layout;
use core::f32;
use std::sync::Arc;

use broker::database::PooledConnection;
use chrono::Utc;
use juniper::{FieldError, FieldResult};
use uuid::Uuid;

use super::schema::{Context, Payload};
use super::update::convert_publish_payload;
use crate::models::Event;

`One`:

Discard existing import groups, and create a single group for everything

use super::schema::{Context, Payload};
use super::update::convert_publish_payload;
use crate::models::Event;
use alloc::alloc::Layout;
use broker::database::PooledConnection;
use chrono::Utc;
use core::f32;
use juniper::{FieldError, FieldResult};
use std::sync::Arc;
use uuid::Uuid;

`reorder_modules`

Reorder mod declarations alphabetically in group.

Default value: true
Possible values: true, false
Stable: Yes

`true` (default)

mod a;
mod b;

mod dolor;
mod ipsum;
mod lorem;
mod sit;

`false`

mod b;
mod a;

mod lorem;
mod ipsum;
mod dolor;
mod sit;

Note mod with #[macro_export] will not be reordered since that could change the semantics of the original source code.

`required_version`

Require a specific version of rustfmt. If you want to make sure that the specific version of rustfmt is used in your CI, use this option.

Default value: CARGO_PKG_VERSION
Possible values: any published version (e.g. "0.3.8")
Stable: No (tracking issue: #3386)

`short_array_element_width_threshold`

The width threshold for an array element to be considered “short”.

The layout of an array is dependent on the length of each of its elements. If the length of every element in an array is below this threshold (all elements are “short”) then the array can be formatted in the mixed/compressed style, but if any one element has a length that exceeds this threshold then the array elements will have to be formatted vertically.

Default value: 10
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

`10` (default):

fn main() {
    pub const FORMAT_TEST: [u64; 5] = [
        0x0000000000000000,
        0xaaaaaaaaaaaaaaaa,
        0xbbbbbbbbbbbbbbbb,
        0xcccccccccccccccc,
        0xdddddddddddddddd,
    ];
}

`20`:

fn main() {
    pub const FORMAT_TEST: [u64; 5] = [
        0x0000000000000000, 0xaaaaaaaaaaaaaaaa, 0xbbbbbbbbbbbbbbbb, 0xcccccccccccccccc,
        0xdddddddddddddddd,
    ];
}

`skip_children`

Don't reformat out of line modules

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3389)

`single_line_if_else_max_width`

Maximum line length for single line if-else expressions. A value of 0 (zero) results in if-else expressions always being broken into multiple lines. Note this occurs when use_small_heuristics is set to Off.

Default value: 50
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for single_line_if_else_max_width will take precedence.

`single_line_let_else_max_width`

Maximum line length for single line let-else statements. See the let-else statement section of the Rust Style Guide for more details on when a let-else statement may be written on a single line. A value of 0 (zero) means the divergent else block will always be formatted over multiple lines. Note this occurs when use_small_heuristics is set to Off.

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for single_line_let_else_max_width will take precedence.

Default value: 50
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

`50` (default):

fn main() {
    let Some(w) = opt else { return Ok(()) };

    let Some(x) = opt else { return };

    let Some(y) = opt else {
        return;
    };

    let Some(z) = some_very_very_very_very_long_name else {
        return;
    };
}

`0`:

fn main() {
    let Some(w) = opt else {
        return Ok(());
    };

    let Some(x) = opt else {
        return;
    };

    let Some(y) = opt else {
        return;
    };

    let Some(z) = some_very_very_very_very_long_name else {
        return;
    };
}

`100`:

fn main() {
    let Some(w) = opt else { return Ok(()) };

    let Some(x) = opt else { return };

    let Some(y) = opt else {
        return;
    };

    let Some(z) = some_very_very_very_very_long_name else { return };
}

`space_after_colon`

Leave a space after the colon.

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3366)

`true` (default):

fn lorem<T: Eq>(t: T) {
    let lorem: Dolor = Lorem {
        ipsum: dolor,
        sit: amet,
    };
}

`false`:

fn lorem<T:Eq>(t:T) {
    let lorem:Dolor = Lorem {
        ipsum:dolor,
        sit:amet,
    };
}

`space_before_colon`

Leave a space before the colon.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3365)

`false` (default):

fn lorem<T: Eq>(t: T) {
    let lorem: Dolor = Lorem {
        ipsum: dolor,
        sit: amet,
    };
}

`true`:

fn lorem<T : Eq>(t : T) {
    let lorem : Dolor = Lorem {
        ipsum : dolor,
        sit : amet,
    };
}

`spaces_around_ranges`

Put spaces around the .., ..=, and ... range operators

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3367)

`false` (default):

fn main() {
    let lorem = 0..10;
    let ipsum = 0..=10;

    match lorem {
        1..5 => foo(),
        _ => bar,
    }

    match lorem {
        1..=5 => foo(),
        _ => bar,
    }

    match lorem {
        1...5 => foo(),
        _ => bar,
    }
}

`true`:

fn main() {
    let lorem = 0 .. 10;
    let ipsum = 0 ..= 10;

    match lorem {
        1 .. 5 => foo(),
        _ => bar,
    }

    match lorem {
        1 ..= 5 => foo(),
        _ => bar,
    }

    match lorem {
        1 ... 5 => foo(),
        _ => bar,
    }
}

`struct_field_align_threshold`

The maximum diff of width between struct fields to be aligned with each other.

Default value : 0
Possible values: any non-negative integer
Stable: No (tracking issue: #3371)

`0` (default):

struct Foo {
    x: u32,
    yy: u32,
    zzz: u32,
}

`20`:

struct Foo {
    x:   u32,
    yy:  u32,
    zzz: u32,
}

`struct_lit_single_line`

Put small struct literals on a single line

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3357)

`true` (default):

fn main() {
    let lorem = Lorem { foo: bar, baz: ofo };
}

`false`:

fn main() {
    let lorem = Lorem {
        foo: bar,
        baz: ofo,
    };
}

`struct_lit_width`

Maximum width in the body of a struct literal before falling back to vertical formatting. A value of 0 (zero) results in struct literals always being broken into multiple lines. Note this occurs when use_small_heuristics is set to Off.

Default value: 18
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for struct_lit_width will take precedence.

`struct_variant_width`

Maximum width in the body of a struct variant before falling back to vertical formatting. A value of 0 (zero) results in struct literals always being broken into multiple lines. Note this occurs when use_small_heuristics is set to Off.

Default value: 35
Possible values: any positive integer that is less than or equal to the value specified for max_width
Stable: Yes

By default this option is set as a percentage of max_width provided by use_small_heuristics, but a value set directly for struct_variant_width will take precedence.

`style_edition`

Controls the edition of the Rust Style Guide to use for formatting (RFC 3338)

Default value: "2015"
Possible values: "2015", "2018", "2021", "2024" (unstable variant)
Stable: No

`tab_spaces`

Number of spaces per tab

Default value: 4
Possible values: any positive integer
Stable: Yes

`4` (default):

fn lorem() {
    let ipsum = dolor();
    let sit = vec![
        "amet consectetur adipiscing elit amet",
        "consectetur adipiscing elit amet consectetur.",
    ];
}

`2`:

fn lorem() {
  let ipsum = dolor();
  let sit = vec![
    "amet consectetur adipiscing elit amet",
    "consectetur adipiscing elit amet consectetur.",
  ];
}

`trailing_comma`

How to handle trailing commas for lists

Default value: "Vertical"
Possible values: "Always", "Never", "Vertical"
Stable: No (tracking issue: #3379)

`"Vertical"` (default):

fn main() {
    let Lorem { ipsum, dolor, sit } = amet;
    let Lorem {
        ipsum,
        dolor,
        sit,
        amet,
        consectetur,
        adipiscing,
    } = elit;
}

`"Always"`:

fn main() {
    let Lorem { ipsum, dolor, sit, } = amet;
    let Lorem {
        ipsum,
        dolor,
        sit,
        amet,
        consectetur,
        adipiscing,
    } = elit;
}

`"Never"`:

fn main() {
    let Lorem { ipsum, dolor, sit } = amet;
    let Lorem {
        ipsum,
        dolor,
        sit,
        amet,
        consectetur,
        adipiscing
    } = elit;
}

`trailing_semicolon`

Add trailing semicolon after break, continue and return

Default value: true
Possible values: true, false
Stable: No (tracking issue: #3378)

`true` (default):

fn foo() -> usize {
    return 0;
}

`false`:

fn foo() -> usize {
    return 0
}

`type_punctuation_density`

Determines if + or = are wrapped in spaces in the punctuation of types

Default value: "Wide"
Possible values: "Compressed", "Wide"
Stable: No (tracking issue: #3364)

`"Wide"` (default):

fn lorem<Ipsum: Dolor + Sit = Amet>() {
    // body
}

`"Compressed"`:

fn lorem<Ipsum: Dolor+Sit=Amet>() {
    // body
}

`unstable_features`

Enable unstable features on the unstable channel.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3387)

`use_field_init_shorthand`

Use field initialize shorthand if possible.

Default value: false
Possible values: true, false
Stable: Yes

`false` (default):

struct Foo {
    x: u32,
    y: u32,
    z: u32,
}

fn main() {
    let x = 1;
    let y = 2;
    let z = 3;
    let a = Foo { x, y, z };
    let b = Foo { x: x, y: y, z: z };
}

`true`:

struct Foo {
    x: u32,
    y: u32,
    z: u32,
}

fn main() {
    let x = 1;
    let y = 2;
    let z = 3;
    let a = Foo { x, y, z };
}

`use_small_heuristics`

This option can be used to simplify the management and bulk updates of the granular width configuration settings (fn_call_width, attr_fn_like_width, struct_lit_width, struct_variant_width, array_width, chain_width, single_line_if_else_max_width), that respectively control when formatted constructs are multi-lined/vertical based on width.

Note that explicitly provided values for the width configuration settings take precedence and override the calculated values determined by use_small_heuristics.

Default value: "Default"
Possible values: "Default", "Off", "Max"
Stable: Yes

`Default` (default):

When use_small_heuristics is set to Default, the values for the granular width settings are calculated as a ratio of the value for max_width.

The ratios are:

fn_call_width - 60%
attr_fn_like_width - 70%
struct_lit_width - 18%
struct_variant_width - 35%
array_width - 60%
chain_width - 60%
single_line_if_else_max_width - 50%
single_line_let_else_max_width - 50%

For example when max_width is set to 100, the width settings are:

fn_call_width=60
attr_fn_like_width=70
struct_lit_width=18
struct_variant_width=35
array_width=60
chain_width=60
single_line_if_else_max_width=50
single_line_let_else_max_width=50

and when max_width is set to 200:

fn_call_width=120
attr_fn_like_width=140
struct_lit_width=36
struct_variant_width=70
array_width=120
chain_width=120
single_line_if_else_max_width=100
single_line_let_else_max_width=100

enum Lorem {
    Ipsum,
    Dolor(bool),
    Sit { amet: Consectetur, adipiscing: Elit },
}

fn main() {
    lorem(
        "lorem",
        "ipsum",
        "dolor",
        "sit",
        "amet",
        "consectetur",
        "adipiscing",
    );

    let lorem = Lorem {
        ipsum: dolor,
        sit: amet,
    };
    let lorem = Lorem { ipsum: dolor };

    let lorem = if ipsum { dolor } else { sit };
}

`Off`:

When use_small_heuristics is set to Off, the granular width settings are functionally disabled and ignored. See the documentation for the respective width config options for specifics.

enum Lorem {
    Ipsum,
    Dolor(bool),
    Sit {
        amet: Consectetur,
        adipiscing: Elit,
    },
}

fn main() {
    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");

    let lorem = Lorem {
        ipsum: dolor,
        sit: amet,
    };

    let lorem = if ipsum {
        dolor
    } else {
        sit
    };
}

`Max`:

When use_small_heuristics is set to Max, then each granular width setting is set to the same value as max_width.

So if max_width is set to 200, then all the width settings are also set to 200.

fn_call_width=200
attr_fn_like_width=200
struct_lit_width=200
struct_variant_width=200
array_width=200
chain_width=200
single_line_if_else_max_width=200
single_line_let_else_max_width=200

enum Lorem {
    Ipsum,
    Dolor(bool),
    Sit { amet: Consectetur, adipiscing: Elit },
}

fn main() {
    lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");

    let lorem = Lorem { ipsum: dolor, sit: amet };

    let lorem = if ipsum { dolor } else { sit };
}

`use_try_shorthand`

Replace uses of the try! macro by the ? shorthand

Default value: false
Possible values: true, false
Stable: Yes

`false` (default):

fn main() {
    let lorem = ipsum.map(|dolor| dolor.sit())?;

    let lorem = try!(ipsum.map(|dolor| dolor.sit()));
}

`true`:

fn main() {
    let lorem = ipsum.map(|dolor| dolor.sit())?;
}

`version`

This option is deprecated and has been replaced by style_edition

Default value: One
Possible values: One, Two
Stable: No (tracking issue: #3383)

Example

version = "Two"

`where_single_line`

Forces the where clause to be laid out on a single line.

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3359)

`false` (default):

impl<T> Lorem for T
where
    Option<T>: Ipsum,
{
    // body
}

`true`:

impl<T> Lorem for T
where Option<T>: Ipsum
{
    // body
}

`wrap_comments`

Break comments to fit on the line

Note that no wrapping will happen if:

The comment is the start of a markdown header doc comment
An URL was found in the comment

Default value: false
Possible values: true, false
Stable: No (tracking issue: #3347)

`false` (default):

// Lorem ipsum dolor sit amet, consectetur adipiscing elit,
// sed do eiusmod tempor incididunt ut labore et dolore
// magna aliqua. Ut enim ad minim veniam, quis nostrud
// exercitation ullamco laboris nisi ut aliquip ex ea
// commodo consequat.

// Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

// Information on the lorem ipsum can be found at the following url: https://en.wikipedia.org/wiki/Lorem_ipsum. Its text is: lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

/// # This doc comment is a very long header (it starts with a '#'). Had it not been a header it would have been wrapped. But because it is a header, it will not be. That is because wrapping a markdown header breaks it.
struct Foo {}

`true`:

// Lorem ipsum dolor sit amet, consectetur adipiscing elit,
// sed do eiusmod tempor incididunt ut labore et dolore
// magna aliqua. Ut enim ad minim veniam, quis nostrud
// exercitation ullamco laboris nisi ut aliquip ex ea
// commodo consequat.

// Lorem ipsum dolor sit amet, consectetur adipiscing elit,
// sed do eiusmod tempor incididunt ut labore et dolore
// magna aliqua. Ut enim ad minim veniam, quis nostrud
// exercitation ullamco laboris nisi ut aliquip ex ea
// commodo consequat.

// Information on the lorem ipsum can be found at the following url: https://en.wikipedia.org/wiki/Lorem_ipsum. Its text is: lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.

/// # This doc comment is a very long header (it starts with a '#'). Had it not been a header it would have been wrapped. But because it is a header, it will not be. That is because wrapping a markdown header breaks it.
struct Foo {}

Internal Options

`emit_mode`

Internal option

`make_backup`

Internal option, use --backup

`print_misformatted_file_names`

Internal option, use -l or --files-with-diff

Configuring Rustfmt

Configuration Options

array_width

attr_fn_like_width

binop_separator

"Front" (default):

"Back":

blank_lines_lower_bound

Example

1

blank_lines_upper_bound

Example

1 (default):

2:

brace_style

Functions

"SameLineWhere" (default):

"AlwaysNextLine":

"PreferSameLine":

Structs and enums

"SameLineWhere" (default):

"AlwaysNextLine":

"PreferSameLine":

chain_width

color

combine_control_expr

true (default):

false:

comment_width

80 (default; comments shorter than comment_width):

60 (comments longer than comment_width):

condense_wildcard_suffixes

false (default):

true:

control_brace_style

"AlwaysSameLine" (default):

"AlwaysNextLine":

"ClosingNextLine":

disable_all_formatting

edition

empty_item_single_line

true (default):

false:

enum_discrim_align_threshold

0 (default):

20:

error_on_line_overflow

error_on_unformatted

fn_args_layout

"Tall" (default):

"Compressed":

"Vertical":

fn_call_width

fn_params_layout

"Tall" (default):

"Compressed":

"Vertical":

fn_single_line

false (default):

true:

force_explicit_abi

true (default):

false:

force_multiline_blocks

false (default):

true:

format_code_in_doc_comments

false (default):

true

doc_comment_code_block_width

format_generated_files

generated_marker_line_search_limit

format_macro_matchers

false (default):

true:

format_macro_bodies

true (default):

false:

skip_macro_invocations

[] (default):

`array_width`

`attr_fn_like_width`

`binop_separator`

`"Front"` (default):

`"Back"`:

`blank_lines_lower_bound`

`1`

`blank_lines_upper_bound`

`1` (default):

`2`:

`brace_style`

`"SameLineWhere"` (default):

`"AlwaysNextLine"`:

`"PreferSameLine"`:

`"SameLineWhere"` (default):

`"AlwaysNextLine"`:

`"PreferSameLine"`:

`chain_width`

`color`

`combine_control_expr`

`true` (default):

`false`:

`comment_width`

`80` (default; comments shorter than `comment_width`):

`60` (comments longer than `comment_width`):

`condense_wildcard_suffixes`

`false` (default):

`true`:

`control_brace_style`

`"AlwaysSameLine"` (default):

`"AlwaysNextLine"`:

`"ClosingNextLine"`:

`disable_all_formatting`

`edition`

`empty_item_single_line`

`true` (default):

`false`:

`enum_discrim_align_threshold`

`0` (default):

`20`:

`error_on_line_overflow`

`error_on_unformatted`

`fn_args_layout`

`"Tall"` (default):

`"Compressed"`:

`"Vertical"`:

`fn_call_width`

`fn_params_layout`

`"Tall"` (default):

`"Compressed"`:

`"Vertical"`:

`fn_single_line`

`false` (default):

`true`:

`force_explicit_abi`

`true` (default):

`false`:

`force_multiline_blocks`

`false` (default):

`true`:

`format_code_in_doc_comments`

`false` (default):

`true`

`doc_comment_code_block_width`

`format_generated_files`

`generated_marker_line_search_limit`

`format_macro_matchers`

`false` (default):

`true`:

`format_macro_bodies`

`true` (default):

`false`:

`skip_macro_invocations`

`[]` (default):

`["lorem"]`:

`["*"]`:

`format_strings`

`false` (default):

`true`:

`hard_tabs`