3 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.
5 A possible content of `rustfmt.toml` or `.rustfmt.toml` might look like this:
9 reorder_imported_names = true
12 Each configuration option is either stable or unstable.
13 Stable options can be used directly, while unstable options are opt-in.
14 To enable unstable options, set `unstable_features = true` in `rustfmt.toml` or pass `--unstable-options` to rustfmt.
16 # Configuration Options
18 Below you find a detailed visual guide on all the supported configuration options of rustfmt:
23 Indent on expressions or items.
25 - **Default value**: `"Block"`
26 - **Possible values**: `"Block"`, `"Visual"`
31 #### `"Block"` (default):
51 let lorem = vec!["ipsum",
63 #### `"Block"` (default):
84 See also: [`control_brace_style`](#control_brace_style).
86 ### Function arguments
88 #### `"Block"` (default):
93 fn lorem(ipsum: usize) {}
113 fn lorem(ipsum: usize) {}
115 fn lorem(ipsum: usize,
128 #### `"Block"` (default):
162 #### `"Block"` (default):
170 Adipiscing: Eq = usize,
171 Consectetur: Eq = usize,
178 adipiscing: Adipiscing,
179 consectetur: Consectetur,
189 fn lorem<Ipsum: Eq = usize,
193 Adipiscing: Eq = usize,
194 Consectetur: Eq = usize,
200 adipiscing: Adipiscing,
201 consectetur: Consectetur,
210 #### `"Block"` (default):
225 let lorem = Lorem { ipsum: dolor,
230 See also: [`struct_lit_single_line`](#struct_lit_single_line), [`indent_style`](#indent_style).
234 #### `"Block"` (default):
237 fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
251 fn lorem<Ipsum, Dolor, Sit, Amet>() -> T
261 ## `use_small_heuristics`
263 Whether to use different formatting for items and expressions if they satisfy a heuristic notion of 'small'.
265 - **Default value**: `true`
266 - **Possible values**: `true`, `false`
269 #### `true` (default):
275 Sit { amet: Consectetur, adipiscing: Elit },
293 let lorem = Lorem { ipsum: dolor };
295 let lorem = if ipsum { dolor } else { sit };
312 lorem("lorem", "ipsum", "dolor", "sit", "amet", "consectetur", "adipiscing");
319 let lorem = if ipsum {
329 Where to put a binary operator when a binary expression goes multiline.
331 - **Default value**: `"Front"`
332 - **Possible values**: `"Front"`, `"Back"`
335 #### `"Front"` (default):
339 let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo
340 || barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;
342 let sum = 123456789012345678901234567890 + 123456789012345678901234567890
343 + 123456789012345678901234567890;
345 let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
346 ..bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
354 let or = foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoo ||
355 barbarbarbarbarbarbarbarbarbarbarbarbarbarbarbar;
357 let sum = 123456789012345678901234567890 + 123456789012345678901234567890 +
358 123456789012345678901234567890;
360 let range = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..
361 bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb;
365 ## `combine_control_expr`
367 Combine control expressions with function calls.
369 - **Default value**: `true`
370 - **Possible values**: `true`, `false`
373 #### `true` (default):
385 foo!(if let Some(..) = x {
398 foo!(while let Some(..) = x {
432 if let Some(..) = x {
449 while let Some(..) = x {
475 Maximum length of comments. No effect unless`wrap_comments = true`.
477 - **Default value**: `80`
478 - **Possible values**: any positive integer
481 **Note:** A value of `0` results in [`wrap_comments`](#wrap_comments) being applied regardless of a line's width.
483 #### `80` (default; comments shorter than `comment_width`):
485 // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
488 #### `60` (comments longer than `comment_width`):
490 // Lorem ipsum dolor sit amet,
491 // consectetur adipiscing elit.
494 See also [`wrap_comments`](#wrap_comments).
496 ## `condense_wildcard_suffixes`
498 Replace strings of _ wildcards by a single .. in tuple patterns
500 - **Default value**: `false`
501 - **Possible values**: `true`, `false`
504 #### `false` (default):
508 let (lorem, ipsum, _, _) = (1, 2, 3, 4);
509 let (lorem, ipsum, ..) = (1, 2, 3, 4);
517 let (lorem, ipsum, ..) = (1, 2, 3, 4);
521 ## `control_brace_style`
523 Brace style for control flow constructs
525 - **Default value**: `"AlwaysSameLine"`
526 - **Possible values**: `"AlwaysNextLine"`, `"AlwaysSameLine"`, `"ClosingNextLine"`
529 #### `"AlwaysSameLine"` (default):
541 #### `"AlwaysNextLine"`:
556 #### `"ClosingNextLine"`:
569 ## `disable_all_formatting`
571 Don't reformat anything
573 - **Default value**: `false`
574 - **Possible values**: `true`, `false`
577 ## `error_on_line_overflow`
579 Error if unable to get all lines within `max_width`
581 - **Default value**: `true`
582 - **Possible values**: `true`, `false`
585 See also [`max_width`](#max_width).
587 ## `error_on_line_overflow_comments`
589 Error if unable to get all comment lines within `comment_width`.
591 - **Default value**: `true`
592 - **Possible values**: `true`, `false`
595 See also [`comment_width`](#comment_width).
599 Argument density in functions
601 - **Default value**: `"Tall"`
602 - **Possible values**: `"Compressed"`, `"Tall"`, `"Vertical"`
605 #### `"Tall"` (default):
609 fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
611 fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
620 consectetur: Consectetur,
621 adipiscing: Adipiscing,
630 consectetur: Consectetur,
631 adipiscing: Adipiscing,
643 fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet);
645 fn lorem(ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet) {
650 ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
651 adipiscing: Adipiscing, elit: Elit,
655 ipsum: Ipsum, dolor: Dolor, sit: Sit, amet: Amet, consectetur: Consectetur,
656 adipiscing: Adipiscing, elit: Elit,
688 consectetur: Consectetur,
689 adipiscing: Adipiscing,
698 consectetur: Consectetur,
699 adipiscing: Adipiscing,
710 Brace style for items
712 - **Default value**: `"SameLineWhere"`
713 - **Possible values**: `"AlwaysNextLine"`, `"PreferSameLine"`, `"SameLineWhere"`
718 #### `"SameLineWhere"` (default):
725 fn lorem(ipsum: usize) {
729 fn lorem<T>(ipsum: T)
731 T: Add + Sub + Mul + Div,
737 #### `"AlwaysNextLine"`:
745 fn lorem(ipsum: usize)
750 fn lorem<T>(ipsum: T)
752 T: Add + Sub + Mul + Div,
758 #### `"PreferSameLine"`:
765 fn lorem(ipsum: usize) {
769 fn lorem<T>(ipsum: T)
771 T: Add + Sub + Mul + Div, {
776 ### Structs and enums
778 #### `"SameLineWhere"` (default):
793 #### `"AlwaysNextLine"`:
809 #### `"PreferSameLine"`:
824 ## `empty_item_single_line`
826 Put empty-body functions and impls on a single line
828 - **Default value**: `true`
829 - **Possible values**: `true`, `false`
832 #### `true` (default):
850 See also [`brace_style`](#brace_style), [`control_brace_style`](#control_brace_style).
855 Put single-expression functions on a single line
857 - **Default value**: `false`
858 - **Possible values**: `true`, `false`
861 #### `false` (default):
864 fn lorem() -> usize {
868 fn lorem() -> usize {
877 fn lorem() -> usize { 42 }
879 fn lorem() -> usize {
885 See also [`control_brace_style`](#control_brace_style).
888 ## `where_single_line`
890 To force single line where layout
892 - **Default value**: `false`
893 - **Possible values**: `true`, `false`
896 #### `false` (default):
911 where Option<T>: Ipsum
917 See also [`brace_style`](#brace_style), [`control_brace_style`](#control_brace_style).
920 ## `force_explicit_abi`
922 Always print the abi for extern items
924 - **Default value**: `true`
925 - **Possible values**: `true`, `false`
928 **Note:** Non-"C" ABIs are always printed. If `false` then "C" is removed.
930 #### `true` (default):
934 pub static lorem: c_int;
942 pub static lorem: c_int;
948 Format string literals where necessary
950 - **Default value**: `false`
951 - **Possible values**: `true`, `false`
954 #### `false` (default):
959 "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet consectetur adipiscing";
967 let lorem = "ipsum dolor sit amet consectetur adipiscing elit lorem ipsum dolor sit amet \
968 consectetur adipiscing";
972 See also [`max_width`](#max_width).
976 Use tab characters for indentation, spaces for alignment
978 - **Default value**: `false`
979 - **Possible values**: `true`, `false`
982 #### `false` (default):
985 fn lorem() -> usize {
986 42 // spaces before 42
993 fn lorem() -> usize {
998 See also: [`tab_spaces`](#tab_spaces).
1003 Indent style of imports
1005 - **Default Value**: `"Visual"`
1006 - **Possible values**: `"Block"`, `"Visual"`
1009 #### `"Visual"` (default):
1012 use foo::{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
1013 zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz};
1020 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
1021 zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz,
1025 See also: [`imports_layout`](#imports_layout).
1029 Item layout inside a imports block
1031 - **Default value**: "Mixed"
1032 - **Possible values**: "Horizontal", "HorizontalVertical", "Mixed", "Vertical"
1035 #### `"Mixed"` (default):
1038 use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};
1040 use foo::{aaaaaaaaaaaaaaaaaa, bbbbbbbbbbbbbbbbbb, cccccccccccccccccc, dddddddddddddddddd,
1041 eeeeeeeeeeeeeeeeee, ffffffffffffffffff};
1044 #### `"Horizontal"`:
1046 **Note**: This option forces all imports onto one line and may exceed `max_width`.
1049 use foo::{xxx, yyy, zzz};
1051 use foo::{aaa, bbb, ccc, ddd, eee, fff};
1054 #### `"HorizontalVertical"`:
1057 use foo::{xxxxxxxxxxxxxxxxxx, yyyyyyyyyyyyyyyyyy, zzzzzzzzzzzzzzzzzz};
1059 use foo::{aaaaaaaaaaaaaaaaaa,
1064 ffffffffffffffffff};
1083 ## `match_block_trailing_comma`
1085 Put a trailing comma after a block based match arm (non-block arms are not affected)
1087 - **Default value**: `false`
1088 - **Possible values**: `true`, `false`
1091 #### `false` (default):
1099 Lorem::Dolor => println!("dolor"),
1112 Lorem::Dolor => println!("dolor"),
1117 See also: [`trailing_comma`](#trailing_comma), [`match_arm_blocks`](#match_arm_blocks).
1121 Maximum width of each line
1123 - **Default value**: `100`
1124 - **Possible values**: any positive integer
1127 See also [`error_on_line_overflow`](#error_on_line_overflow).
1131 Merge multiple derives into a single one.
1133 - **Default value**: `true`
1134 - **Possible values**: `true`, `false`
1137 #### `true` (default):
1140 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
1147 #[derive(Eq, PartialEq)]
1149 #[derive(Copy, Clone)]
1153 ## `force_multiline_blocks`
1155 Force multiline closure and match arm bodies to be wrapped in a block
1157 - **Default value**: `false`
1158 - **Possible values**: `false`, `true`
1161 #### `false` (default):
1165 result.and_then(|maybe_value| match maybe_value {
1167 Some(value) => bar(),
1172 println!("Hello World");
1174 Some(dolor) => foo(),
1183 result.and_then(|maybe_value| {
1193 println!("Hello World");
1203 Unix or Windows line endings
1205 - **Default value**: `"Unix"`
1206 - **Possible values**: `"Native"`, `"Unix"`, `"Windows"`
1209 ## `normalize_comments`
1211 Convert /* */ comments to // comments where possible
1213 - **Default value**: `false`
1214 - **Possible values**: `true`, `false`
1217 #### `false` (default):
1221 fn dolor() -> usize {}
1224 fn adipiscing() -> usize {}
1231 fn dolor() -> usize {}
1234 fn adipiscing() -> usize {}
1237 ## `reorder_imported_names`
1239 Reorder lists of names in import statements alphabetically
1241 - **Default value**: `false`
1242 - **Possible values**: `true`, `false`
1245 #### `false` (default):
1248 use super::{lorem, ipsum, dolor, sit};
1254 use super::{dolor, ipsum, lorem, sit};
1257 See also [`reorder_imports`](#reorder_imports).
1259 ## `reorder_imports`
1261 Reorder import statements alphabetically
1263 - **Default value**: `false`
1264 - **Possible values**: `true`, `false`
1267 #### `false` (default):
1285 See also [`reorder_imported_names`](#reorder_imported_names), [`reorder_imports_in_group`](#reorder_imports_in_group).
1287 ## `reorder_imports_in_group`
1289 Reorder import statements in group
1291 - **Default value**: `false`
1292 - **Possible values**: `true`, `false`
1295 **Note:** This option takes effect only when [`reorder_imports`](#reorder_imports) is set to `true`.
1297 #### `false` (default):
1321 See also [`reorder_imports`](#reorder_imports).
1323 ## `reorder_extern_crates`
1325 Reorder `extern crate` statements alphabetically
1327 - **Default value**: `true`
1328 - **Possible values**: `true`, `false`
1331 #### `true` (default):
1349 See also [`reorder_extern_crates_in_group`](#reorder_extern_crates_in_group).
1351 ## `reorder_extern_crates_in_group`
1353 Reorder `extern crate` statements in group
1355 - **Default value**: `true`
1356 - **Possible values**: `true`, `false`
1359 **Note:** This option takes effect only when [`reorder_imports`](#reorder_imports) is set to `true`.
1361 #### `true` (default):
1385 See also [`reorder_extern_crates`](#reorder_extern_crates).
1389 Report `TODO` items in comments.
1391 - **Default value**: `"Never"`
1392 - **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
1395 Warns about any comments containing `TODO` in them when set to `"Always"`. If
1396 it contains a `#X` (with `X` being a number) in parentheses following the
1397 `TODO`, `"Unnumbered"` will ignore it.
1399 See also [`report_fixme`](#report_fixme).
1403 Report `FIXME` items in comments.
1405 - **Default value**: `"Never"`
1406 - **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
1409 Warns about any comments containing `FIXME` in them when set to `"Always"`. If
1410 it contains a `#X` (with `X` being a number) in parentheses following the
1411 `FIXME`, `"Unnumbered"` will ignore it.
1413 See also [`report_todo`](#report_todo).
1418 Don't reformat out of line modules
1420 - **Default value**: `false`
1421 - **Possible values**: `true`, `false`
1424 ## `space_after_colon`
1426 Leave a space after the colon.
1428 - **Default value**: `true`
1429 - **Possible values**: `true`, `false`
1432 #### `true` (default):
1435 fn lorem<T: Eq>(t: T) {
1436 let lorem: Dolor = Lorem {
1446 fn lorem<T:Eq>(t:T) {
1447 let lorem:Dolor = Lorem {
1454 See also: [`space_before_colon`](#space_before_colon).
1456 ## `space_before_colon`
1458 Leave a space before the colon.
1460 - **Default value**: `false`
1461 - **Possible values**: `true`, `false`
1464 #### `false` (default):
1467 fn lorem<T: Eq>(t: T) {
1468 let lorem: Dolor = Lorem {
1478 fn lorem<T : Eq>(t : T) {
1479 let lorem : Dolor = Lorem {
1486 See also: [`space_after_colon`](#space_after_colon).
1488 ## `struct_field_align_threshold`
1490 The maximum diff of width between struct fields to be aligned with each other.
1492 - **Default value** : 0
1493 - **Possible values**: any positive integer
1516 ## `spaces_around_ranges`
1518 Put spaces around the .., ..=, and ... range operators
1520 - **Default value**: `false`
1521 - **Possible values**: `true`, `false`
1524 #### `false` (default):
1552 let lorem = 0 .. 10;
1553 let ipsum = 0 ..= 10;
1572 ## `spaces_within_parens_and_brackets`
1574 Put spaces within non-empty generic arguments, parentheses, and square brackets
1576 - **Default value**: `false`
1577 - **Possible values**: `true`, `false`
1580 #### `false` (default):
1583 // generic arguments
1584 fn lorem<T: Eq>(t: T) {
1588 // non-empty parentheses
1589 fn lorem<T: Eq>(t: T) {
1590 let lorem = (ipsum, dolor);
1593 // non-empty square brackets
1594 let lorem: [usize; 2] = [ipsum, dolor];
1600 // generic arguments
1601 fn lorem< T: Eq >(t: T) {
1605 // non-empty parentheses
1606 fn lorem<T: Eq>( t: T ) {
1607 let lorem = ( ipsum, dolor );
1610 // non-empty square brackets
1611 let lorem: [ usize; 2 ] = [ ipsum, dolor ];
1614 ## `struct_lit_single_line`
1616 Put small struct literals on a single line
1618 - **Default value**: `true`
1619 - **Possible values**: `true`, `false`
1622 #### `true` (default):
1625 let lorem = Lorem { ipsum: dolor, sit: amet };
1637 See also: [`indent_style`](#indent_style).
1642 Number of spaces per tab
1644 - **Default value**: `4`
1645 - **Possible values**: any positive integer
1652 let ipsum = dolor();
1654 "amet consectetur adipiscing elit."
1663 let ipsum = dolor();
1665 "amet consectetur adipiscing elit."
1670 See also: [`hard_tabs`](#hard_tabs).
1675 How to handle trailing commas for lists
1677 - **Default value**: `"Vertical"`
1678 - **Possible values**: `"Always"`, `"Never"`, `"Vertical"`
1681 #### `"Vertical"` (default):
1684 let Lorem { ipsum, dolor, sit } = amet;
1698 let Lorem { ipsum, dolor, sit, } = amet;
1712 let Lorem { ipsum, dolor, sit } = amet;
1723 See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
1725 ## `trailing_semicolon`
1727 Add trailing semicolon after break, continue and return
1729 - **Default value**: `true`
1730 - **Possible values**: `true`, `false`
1733 #### `true` (default):
1747 ## `type_punctuation_density`
1749 Determines if `+` or `=` are wrapped in spaces in the punctuation of types
1751 - **Default value**: `"Wide"`
1752 - **Possible values**: `"Compressed"`, `"Wide"`
1755 #### `"Wide"` (default):
1758 fn lorem<Ipsum: Dolor + Sit = Amet>() {
1763 #### `"Compressed"`:
1766 fn lorem<Ipsum: Dolor+Sit=Amet>() {
1771 ## `use_try_shorthand`
1773 Replace uses of the try! macro by the ? shorthand
1775 - **Default value**: `false`
1776 - **Possible values**: `true`, `false`
1779 #### `false` (default):
1782 let lorem = try!(ipsum.map(|dolor|dolor.sit()));
1788 let lorem = ipsum.map(|dolor| dolor.sit())?;
1794 Break comments to fit on the line
1796 - **Default value**: `false`
1797 - **Possible values**: `true`, `false`
1800 #### `false` (default):
1803 // 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.
1809 // Lorem ipsum dolor sit amet, consectetur adipiscing elit,
1810 // sed do eiusmod tempor incididunt ut labore et dolore
1811 // magna aliqua. Ut enim ad minim veniam, quis nostrud
1812 // exercitation ullamco laboris nisi ut aliquip ex ea
1813 // commodo consequat.
1816 ## `match_arm_blocks`
1818 Wrap the body of arms in blocks when it does not fit on the same line with the pattern of arms
1820 - **Default value**: `true`
1821 - **Possible values**: `true`, `false`
1824 #### `true` (default):
1829 foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
1831 false => println!("{}", sit),
1840 foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
1841 false => println!("{}", sit),
1845 See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
1849 What Write Mode to use when none is supplied: Replace, Overwrite, Display, Diff, Coverage
1851 - **Default value**: `"Overwrite"`
1852 - **Possible values**: `"Checkstyle"`, `"Coverage"`, `"Diff"`, `"Display"`, `"Overwrite"`, `"Plain"`, `"Replace"`
1855 ## `blank_lines_upper_bound`
1857 Maximum number of blank lines which can be put between items. If more than this number of consecutive empty
1858 lines are found, they are trimmed down to match this integer.
1860 - **Default value**: `1`
1861 - **Possible values**: *unsigned integer*
1910 See also: [`blank_lines_lower_bound`](#blank_lines_lower_bound)
1912 ## `blank_lines_lower_bound`
1914 Minimum number of blank lines which must be put between items. If two items have fewer blank lines between
1915 them, additional blank lines are inserted.
1917 - **Default value**: `0`
1918 - **Possible values**: *unsigned integer*
1922 Original Code (rustfmt will not change it with the default value of `0`):