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):
1164 result.and_then(|maybe_value| match maybe_value {
1171 println!("Hello World");
1181 result.and_then(|maybe_value| {
1191 println!("Hello World");
1201 Unix or Windows line endings
1203 - **Default value**: `"Unix"`
1204 - **Possible values**: `"Native"`, `"Unix"`, `"Windows"`
1207 ## `normalize_comments`
1209 Convert /* */ comments to // comments where possible
1211 - **Default value**: `false`
1212 - **Possible values**: `true`, `false`
1215 #### `false` (default):
1219 fn dolor() -> usize {}
1222 fn adipiscing() -> usize {}
1229 fn dolor() -> usize {}
1232 fn adipiscing() -> usize {}
1235 ## `reorder_imported_names`
1237 Reorder lists of names in import statements alphabetically
1239 - **Default value**: `false`
1240 - **Possible values**: `true`, `false`
1243 #### `false` (default):
1246 use super::{lorem, ipsum, dolor, sit};
1252 use super::{dolor, ipsum, lorem, sit};
1255 See also [`reorder_imports`](#reorder_imports).
1257 ## `reorder_imports`
1259 Reorder import statements alphabetically
1261 - **Default value**: `false`
1262 - **Possible values**: `true`, `false`
1265 #### `false` (default):
1283 See also [`reorder_imported_names`](#reorder_imported_names), [`reorder_imports_in_group`](#reorder_imports_in_group).
1285 ## `reorder_imports_in_group`
1287 Reorder import statements in group
1289 - **Default value**: `false`
1290 - **Possible values**: `true`, `false`
1293 **Note:** This option takes effect only when [`reorder_imports`](#reorder_imports) is set to `true`.
1295 #### `false` (default):
1319 See also [`reorder_imports`](#reorder_imports).
1321 ## `reorder_extern_crates`
1323 Reorder `extern crate` statements alphabetically
1325 - **Default value**: `true`
1326 - **Possible values**: `true`, `false`
1329 #### `true` (default):
1347 See also [`reorder_extern_crates_in_group`](#reorder_extern_crates_in_group).
1349 ## `reorder_extern_crates_in_group`
1351 Reorder `extern crate` statements in group
1353 - **Default value**: `true`
1354 - **Possible values**: `true`, `false`
1357 **Note:** This option takes effect only when [`reorder_imports`](#reorder_imports) is set to `true`.
1359 #### `true` (default):
1383 See also [`reorder_extern_crates`](#reorder_extern_crates).
1387 Report `TODO` items in comments.
1389 - **Default value**: `"Never"`
1390 - **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
1393 Warns about any comments containing `TODO` in them when set to `"Always"`. If
1394 it contains a `#X` (with `X` being a number) in parentheses following the
1395 `TODO`, `"Unnumbered"` will ignore it.
1397 See also [`report_fixme`](#report_fixme).
1401 Report `FIXME` items in comments.
1403 - **Default value**: `"Never"`
1404 - **Possible values**: `"Always"`, `"Unnumbered"`, `"Never"`
1407 Warns about any comments containing `FIXME` in them when set to `"Always"`. If
1408 it contains a `#X` (with `X` being a number) in parentheses following the
1409 `FIXME`, `"Unnumbered"` will ignore it.
1411 See also [`report_todo`](#report_todo).
1416 Don't reformat out of line modules
1418 - **Default value**: `false`
1419 - **Possible values**: `true`, `false`
1422 ## `space_after_colon`
1424 Leave a space after the colon.
1426 - **Default value**: `true`
1427 - **Possible values**: `true`, `false`
1430 #### `true` (default):
1433 fn lorem<T: Eq>(t: T) {
1434 let lorem: Dolor = Lorem {
1444 fn lorem<T:Eq>(t:T) {
1445 let lorem:Dolor = Lorem {
1452 See also: [`space_before_colon`](#space_before_colon).
1454 ## `space_before_colon`
1456 Leave a space before the colon.
1458 - **Default value**: `false`
1459 - **Possible values**: `true`, `false`
1462 #### `false` (default):
1465 fn lorem<T: Eq>(t: T) {
1466 let lorem: Dolor = Lorem {
1476 fn lorem<T : Eq>(t : T) {
1477 let lorem : Dolor = Lorem {
1484 See also: [`space_after_colon`](#space_after_colon).
1486 ## `struct_field_align_threshold`
1488 The maximum diff of width between struct fields to be aligned with each other.
1490 - **Default value** : 0
1491 - **Possible values**: any positive integer
1514 ## `spaces_around_ranges`
1516 Put spaces around the .., ..=, and ... range operators
1518 - **Default value**: `false`
1519 - **Possible values**: `true`, `false`
1522 #### `false` (default):
1550 let lorem = 0 .. 10;
1551 let ipsum = 0 ..= 10;
1570 ## `spaces_within_parens_and_brackets`
1572 Put spaces within non-empty generic arguments, parentheses, and square brackets
1574 - **Default value**: `false`
1575 - **Possible values**: `true`, `false`
1578 #### `false` (default):
1581 // generic arguments
1582 fn lorem<T: Eq>(t: T) {
1586 // non-empty parentheses
1587 fn lorem<T: Eq>(t: T) {
1588 let lorem = (ipsum, dolor);
1591 // non-empty square brackets
1592 let lorem: [usize; 2] = [ipsum, dolor];
1598 // generic arguments
1599 fn lorem< T: Eq >(t: T) {
1603 // non-empty parentheses
1604 fn lorem<T: Eq>( t: T ) {
1605 let lorem = ( ipsum, dolor );
1608 // non-empty square brackets
1609 let lorem: [ usize; 2 ] = [ ipsum, dolor ];
1612 ## `struct_lit_single_line`
1614 Put small struct literals on a single line
1616 - **Default value**: `true`
1617 - **Possible values**: `true`, `false`
1620 #### `true` (default):
1623 let lorem = Lorem { ipsum: dolor, sit: amet };
1635 See also: [`indent_style`](#indent_style).
1640 Number of spaces per tab
1642 - **Default value**: `4`
1643 - **Possible values**: any positive integer
1650 let ipsum = dolor();
1652 "amet consectetur adipiscing elit."
1661 let ipsum = dolor();
1663 "amet consectetur adipiscing elit."
1668 See also: [`hard_tabs`](#hard_tabs).
1673 How to handle trailing commas for lists
1675 - **Default value**: `"Vertical"`
1676 - **Possible values**: `"Always"`, `"Never"`, `"Vertical"`
1679 #### `"Vertical"` (default):
1682 let Lorem { ipsum, dolor, sit } = amet;
1696 let Lorem { ipsum, dolor, sit, } = amet;
1710 let Lorem { ipsum, dolor, sit } = amet;
1721 See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
1723 ## `trailing_semicolon`
1725 Add trailing semicolon after break, continue and return
1727 - **Default value**: `true`
1728 - **Possible values**: `true`, `false`
1731 #### `true` (default):
1745 ## `type_punctuation_density`
1747 Determines if `+` or `=` are wrapped in spaces in the punctuation of types
1749 - **Default value**: `"Wide"`
1750 - **Possible values**: `"Compressed"`, `"Wide"`
1753 #### `"Wide"` (default):
1756 fn lorem<Ipsum: Dolor + Sit = Amet>() {
1761 #### `"Compressed"`:
1764 fn lorem<Ipsum: Dolor+Sit=Amet>() {
1769 ## `use_try_shorthand`
1771 Replace uses of the try! macro by the ? shorthand
1773 - **Default value**: `false`
1774 - **Possible values**: `true`, `false`
1777 #### `false` (default):
1780 let lorem = try!(ipsum.map(|dolor|dolor.sit()));
1786 let lorem = ipsum.map(|dolor| dolor.sit())?;
1792 Break comments to fit on the line
1794 - **Default value**: `false`
1795 - **Possible values**: `true`, `false`
1798 #### `false` (default):
1801 // 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.
1807 // Lorem ipsum dolor sit amet, consectetur adipiscing elit,
1808 // sed do eiusmod tempor incididunt ut labore et dolore
1809 // magna aliqua. Ut enim ad minim veniam, quis nostrud
1810 // exercitation ullamco laboris nisi ut aliquip ex ea
1811 // commodo consequat.
1814 ## `match_arm_blocks`
1816 Wrap the body of arms in blocks when it does not fit on the same line with the pattern of arms
1818 - **Default value**: `true`
1819 - **Possible values**: `true`, `false`
1822 #### `true` (default):
1827 foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
1829 false => println!("{}", sit),
1838 foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
1839 false => println!("{}", sit),
1843 See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
1847 What Write Mode to use when none is supplied: Replace, Overwrite, Display, Diff, Coverage
1849 - **Default value**: `"Overwrite"`
1850 - **Possible values**: `"Checkstyle"`, `"Coverage"`, `"Diff"`, `"Display"`, `"Overwrite"`, `"Plain"`, `"Replace"`
1853 ## `blank_lines_upper_bound`
1855 Maximum number of blank lines which can be put between items. If more than this number of consecutive empty
1856 lines are found, they are trimmed down to match this integer.
1858 - **Default value**: `1`
1859 - **Possible values**: *unsigned integer*
1908 See also: [`blank_lines_lower_bound`](#blank_lines_lower_bound)
1910 ## `blank_lines_lower_bound`
1912 Minimum number of blank lines which must be put between items. If two items have fewer blank lines between
1913 them, additional blank lines are inserted.
1915 - **Default value**: `0`
1916 - **Possible values**: *unsigned integer*
1920 Original Code (rustfmt will not change it with the default value of `0`):