src/lists.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Format list-like expressions and items.
  12
  13 use std::cmp;
  14 use std::iter::Peekable;
  15
  16 use config::lists::*;
  17 use syntax::codemap::BytePos;
  18
  19 use comment::{find_comment_end, rewrite_comment, FindUncommented};
  20 use config::{Config, IndentStyle};
  21 use rewrite::RewriteContext;
  22 use shape::{Indent, Shape};
  23 use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
  24 use visitor::SnippetProvider;
  25
  26 pub struct ListFormatting<'a> {
  27     pub tactic: DefinitiveListTactic,
  28     pub separator: &'a str,
  29     pub trailing_separator: SeparatorTactic,
  30     pub separator_place: SeparatorPlace,
  31     pub shape: Shape,
  32     // Non-expressions, e.g. items, will have a new line at the end of the list.
  33     // Important for comment styles.
  34     pub ends_with_newline: bool,
  35     // Remove newlines between list elements for expressions.
  36     pub preserve_newline: bool,
  37     pub config: &'a Config,
  38 }
  39
  40 impl<'a> ListFormatting<'a> {
  41     pub fn needs_trailing_separator(&self) -> bool {
  42         match self.trailing_separator {
  43             // We always put separator in front.
  44             SeparatorTactic::Always => true,
  45             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
  46             SeparatorTactic::Never => {
  47                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
  48             }
  49         }
  50     }
  51 }
  52
  53 impl AsRef<ListItem> for ListItem {
  54     fn as_ref(&self) -> &ListItem {
  55         self
  56     }
  57 }
  58
  59 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
  60 pub enum ListItemCommentStyle {
  61     // Try to keep the comment on the same line with the item.
  62     SameLine,
  63     // Put the comment on the previous or the next line of the item.
  64     DifferentLine,
  65     // No comment available.
  66     None,
  67 }
  68
  69 #[derive(Debug, Clone)]
  70 pub struct ListItem {
  71     // None for comments mean that they are not present.
  72     pub pre_comment: Option<String>,
  73     pub pre_comment_style: ListItemCommentStyle,
  74     // Item should include attributes and doc comments. None indicates a failed
  75     // rewrite.
  76     pub item: Option<String>,
  77     pub post_comment: Option<String>,
  78     // Whether there is extra whitespace before this item.
  79     pub new_lines: bool,
  80 }
  81
  82 impl ListItem {
  83     pub fn inner_as_ref(&self) -> &str {
  84         self.item.as_ref().map_or("", |s| s)
  85     }
  86
  87     pub fn is_different_group(&self) -> bool {
  88         self.inner_as_ref().contains('\n') || self.pre_comment.is_some()
  89             || self.post_comment
  90                 .as_ref()
  91                 .map_or(false, |s| s.contains('\n'))
  92     }
  93
  94     pub fn is_multiline(&self) -> bool {
  95         self.inner_as_ref().contains('\n')
  96             || self.pre_comment
  97                 .as_ref()
  98                 .map_or(false, |s| s.contains('\n'))
  99             || self.post_comment
 100                 .as_ref()
 101                 .map_or(false, |s| s.contains('\n'))
 102     }
 103
 104     pub fn has_single_line_comment(&self) -> bool {
 105         self.pre_comment
 106             .as_ref()
 107             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 108             || self.post_comment
 109                 .as_ref()
 110                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 111     }
 112
 113     pub fn has_comment(&self) -> bool {
 114         self.pre_comment.is_some() || self.post_comment.is_some()
 115     }
 116
 117     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 118         ListItem {
 119             pre_comment: None,
 120             pre_comment_style: ListItemCommentStyle::None,
 121             item: Some(s.into()),
 122             post_comment: None,
 123             new_lines: false,
 124         }
 125     }
 126
 127     // true if the item causes something to be written.
 128     fn is_substantial(&self) -> bool {
 129         fn empty(s: &Option<String>) -> bool {
 130             match *s {
 131                 Some(ref s) if !s.is_empty() => false,
 132                 _ => true,
 133             }
 134         }
 135
 136         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 137     }
 138 }
 139
 140 /// The type of separator for lists.
 141 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 142 pub enum Separator {
 143     Comma,
 144     VerticalBar,
 145 }
 146
 147 impl Separator {
 148     pub fn len(&self) -> usize {
 149         match *self {
 150             // 2 = `, `
 151             Separator::Comma => 2,
 152             // 3 = ` | `
 153             Separator::VerticalBar => 3,
 154         }
 155     }
 156 }
 157
 158 pub fn definitive_tactic<I, T>(
 159     items: I,
 160     tactic: ListTactic,
 161     sep: Separator,
 162     width: usize,
 163 ) -> DefinitiveListTactic
 164 where
 165     I: IntoIterator<Item = T> + Clone,
 166     T: AsRef<ListItem>,
 167 {
 168     let pre_line_comments = items
 169         .clone()
 170         .into_iter()
 171         .any(|item| item.as_ref().has_single_line_comment());
 172
 173     let limit = match tactic {
 174         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 175         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 176         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 177         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 178         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 179     };
 180
 181     let (sep_count, total_width) = calculate_width(items.clone());
 182     let total_sep_len = sep.len() * sep_count.checked_sub(1).unwrap_or(0);
 183     let real_total = total_width + total_sep_len;
 184
 185     if real_total <= limit && !pre_line_comments
 186         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 187     {
 188         DefinitiveListTactic::Horizontal
 189     } else {
 190         match tactic {
 191             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 192             _ => DefinitiveListTactic::Vertical,
 193         }
 194     }
 195 }
 196
 197 // Format a list of commented items into a string.
 198 // TODO: add unit tests
 199 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 200 where
 201     I: IntoIterator<Item = T> + Clone,
 202     T: AsRef<ListItem>,
 203 {
 204     let tactic = formatting.tactic;
 205     let sep_len = formatting.separator.len();
 206
 207     // Now that we know how we will layout, we can decide for sure if there
 208     // will be a trailing separator.
 209     let mut trailing_separator = formatting.needs_trailing_separator();
 210     let mut result = String::with_capacity(128);
 211     let cloned_items = items.clone();
 212     let mut iter = items.into_iter().enumerate().peekable();
 213     let mut item_max_width: Option<usize> = None;
 214     let sep_place =
 215         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 216
 217     let mut line_len = 0;
 218     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 219     while let Some((i, item)) = iter.next() {
 220         let item = item.as_ref();
 221         let inner_item = item.item.as_ref()?;
 222         let first = i == 0;
 223         let last = iter.peek().is_none();
 224         let mut separate = match sep_place {
 225             SeparatorPlace::Front => !first,
 226             SeparatorPlace::Back => !last || trailing_separator,
 227         };
 228         let item_sep_len = if separate { sep_len } else { 0 };
 229
 230         // Item string may be multi-line. Its length (used for block comment alignment)
 231         // should be only the length of the last line.
 232         let item_last_line = if item.is_multiline() {
 233             inner_item.lines().last().unwrap_or("")
 234         } else {
 235             inner_item.as_ref()
 236         };
 237         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 238         if item_last_line.starts_with(&**indent_str) {
 239             item_last_line_width -= indent_str.len();
 240         }
 241
 242         if !item.is_substantial() {
 243             continue;
 244         }
 245
 246         match tactic {
 247             DefinitiveListTactic::Horizontal if !first => {
 248                 result.push(' ');
 249             }
 250             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 251                 if i == 0 {
 252                     // Nothing
 253                 } else if i < num_args_before {
 254                     result.push(' ');
 255                 } else if i <= num_args_before + 1 {
 256                     result.push('\n');
 257                     result.push_str(indent_str);
 258                 } else {
 259                     result.push(' ');
 260                 }
 261             }
 262             DefinitiveListTactic::Vertical
 263                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 264             {
 265                 result.push('\n');
 266                 result.push_str(indent_str);
 267             }
 268             DefinitiveListTactic::Mixed => {
 269                 let total_width = total_item_width(item) + item_sep_len;
 270
 271                 // 1 is space between separator and item.
 272                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 273                     result.push('\n');
 274                     result.push_str(indent_str);
 275                     line_len = 0;
 276                     if formatting.ends_with_newline {
 277                         trailing_separator = true;
 278                     }
 279                 }
 280
 281                 if last && formatting.ends_with_newline {
 282                     match formatting.trailing_separator {
 283                         SeparatorTactic::Always | SeparatorTactic::Vertical => separate = true,
 284                         _ => (),
 285                     }
 286                 }
 287
 288                 if line_len > 0 {
 289                     result.push(' ');
 290                     line_len += 1;
 291                 }
 292
 293                 line_len += total_width;
 294             }
 295             _ => {}
 296         }
 297
 298         // Pre-comments
 299         if let Some(ref comment) = item.pre_comment {
 300             // Block style in non-vertical mode.
 301             let block_mode = tactic != DefinitiveListTactic::Vertical;
 302             // Width restriction is only relevant in vertical mode.
 303             let comment =
 304                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 305             result.push_str(&comment);
 306
 307             if !inner_item.is_empty() {
 308                 if tactic == DefinitiveListTactic::Vertical {
 309                     // We cannot keep pre-comments on the same line if the comment if normalized.
 310                     let keep_comment = if formatting.config.normalize_comments()
 311                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 312                     {
 313                         false
 314                     } else {
 315                         // We will try to keep the comment on the same line with the item here.
 316                         // 1 = ` `
 317                         let total_width = total_item_width(item) + item_sep_len + 1;
 318                         total_width <= formatting.shape.width
 319                     };
 320                     if keep_comment {
 321                         result.push(' ');
 322                     } else {
 323                         result.push('\n');
 324                         result.push_str(indent_str);
 325                     }
 326                 } else {
 327                     result.push(' ');
 328                 }
 329             }
 330             item_max_width = None;
 331         }
 332
 333         if separate && sep_place.is_front() && !first {
 334             result.push_str(formatting.separator.trim());
 335             result.push(' ');
 336         }
 337         result.push_str(inner_item);
 338
 339         // Post-comments
 340         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 341             let comment = item.post_comment.as_ref().unwrap();
 342             let formatted_comment = rewrite_comment(
 343                 comment,
 344                 true,
 345                 Shape::legacy(formatting.shape.width, Indent::empty()),
 346                 formatting.config,
 347             )?;
 348
 349             result.push(' ');
 350             result.push_str(&formatted_comment);
 351         }
 352
 353         if separate && sep_place.is_back() {
 354             result.push_str(formatting.separator);
 355         }
 356
 357         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 358             let comment = item.post_comment.as_ref().unwrap();
 359             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 360
 361             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 362                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 363                     *item_max_width = Some(max_width_of_item_with_post_comment(
 364                         &cloned_items,
 365                         i,
 366                         overhead,
 367                         formatting.config.max_width(),
 368                     ));
 369                 }
 370                 let overhead = if starts_with_newline(comment) {
 371                     0
 372                 } else if let Some(max_width) = *item_max_width {
 373                     max_width + 2
 374                 } else {
 375                     // 1 = space between item and comment.
 376                     item_last_line_width + 1
 377                 };
 378                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 379                 let offset = formatting.shape.indent + overhead;
 380                 let comment_shape = Shape::legacy(width, offset);
 381
 382                 // Use block-style only for the last item or multiline comments.
 383                 let block_style = !formatting.ends_with_newline && last
 384                     || comment.trim().contains('\n')
 385                     || comment.trim().len() > width;
 386
 387                 rewrite_comment(
 388                     comment.trim_left(),
 389                     block_style,
 390                     comment_shape,
 391                     formatting.config,
 392                 )
 393             };
 394
 395             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 396
 397             if !starts_with_newline(comment) {
 398                 let mut comment_alignment =
 399                     post_comment_alignment(item_max_width, inner_item.len());
 400                 if first_line_width(&formatted_comment) + last_line_width(&result)
 401                     + comment_alignment + 1 > formatting.config.max_width()
 402                 {
 403                     item_max_width = None;
 404                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 405                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 406                 }
 407                 for _ in 0..(comment_alignment + 1) {
 408                     result.push(' ');
 409                 }
 410                 // An additional space for the missing trailing separator.
 411                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 412                 {
 413                     result.push(' ');
 414                 }
 415             } else {
 416                 result.push('\n');
 417                 result.push_str(indent_str);
 418             }
 419             if formatted_comment.contains('\n') {
 420                 item_max_width = None;
 421             }
 422             result.push_str(&formatted_comment);
 423         } else {
 424             item_max_width = None;
 425         }
 426
 427         if formatting.preserve_newline && !last && tactic == DefinitiveListTactic::Vertical
 428             && item.new_lines
 429         {
 430             item_max_width = None;
 431             result.push('\n');
 432         }
 433     }
 434
 435     Some(result)
 436 }
 437
 438 fn max_width_of_item_with_post_comment<I, T>(
 439     items: &I,
 440     i: usize,
 441     overhead: usize,
 442     max_budget: usize,
 443 ) -> usize
 444 where
 445     I: IntoIterator<Item = T> + Clone,
 446     T: AsRef<ListItem>,
 447 {
 448     let mut max_width = 0;
 449     let mut first = true;
 450     for item in items.clone().into_iter().skip(i) {
 451         let item = item.as_ref();
 452         let inner_item_width = item.inner_as_ref().len();
 453         if !first
 454             && (item.is_different_group() || !item.post_comment.is_some()
 455                 || inner_item_width + overhead > max_budget)
 456         {
 457             return max_width;
 458         }
 459         if max_width < inner_item_width {
 460             max_width = inner_item_width;
 461         }
 462         if item.new_lines {
 463             return max_width;
 464         }
 465         first = false;
 466     }
 467     max_width
 468 }
 469
 470 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 471     item_max_width
 472         .and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
 473         .unwrap_or(0)
 474 }
 475
 476 pub struct ListItems<'a, I, F1, F2, F3>
 477 where
 478     I: Iterator,
 479 {
 480     snippet_provider: &'a SnippetProvider<'a>,
 481     inner: Peekable<I>,
 482     get_lo: F1,
 483     get_hi: F2,
 484     get_item_string: F3,
 485     prev_span_end: BytePos,
 486     next_span_start: BytePos,
 487     terminator: &'a str,
 488     separator: &'a str,
 489     leave_last: bool,
 490 }
 491
 492 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 493 where
 494     I: Iterator<Item = T>,
 495     F1: Fn(&T) -> BytePos,
 496     F2: Fn(&T) -> BytePos,
 497     F3: Fn(&T) -> Option<String>,
 498 {
 499     type Item = ListItem;
 500
 501     fn next(&mut self) -> Option<Self::Item> {
 502         let white_space: &[_] = &[' ', '\t'];
 503
 504         self.inner.next().map(|item| {
 505             let mut new_lines = false;
 506             // Pre-comment
 507             let pre_snippet = self.snippet_provider
 508                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 509                 .unwrap();
 510             let trimmed_pre_snippet = pre_snippet.trim();
 511             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 512             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 513             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 514                 (
 515                     Some(trimmed_pre_snippet.to_owned()),
 516                     ListItemCommentStyle::DifferentLine,
 517                 )
 518             } else if has_block_comment {
 519                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 520                 if pre_snippet
 521                     .chars()
 522                     .rev()
 523                     .take(comment_end + 1)
 524                     .any(|c| c == '\n')
 525                 {
 526                     (
 527                         Some(trimmed_pre_snippet.to_owned()),
 528                         ListItemCommentStyle::DifferentLine,
 529                     )
 530                 } else {
 531                     (
 532                         Some(trimmed_pre_snippet.to_owned()),
 533                         ListItemCommentStyle::SameLine,
 534                     )
 535                 }
 536             } else {
 537                 (None, ListItemCommentStyle::None)
 538             };
 539
 540             // Post-comment
 541             let next_start = match self.inner.peek() {
 542                 Some(next_item) => (self.get_lo)(next_item),
 543                 None => self.next_span_start,
 544             };
 545             let post_snippet = self.snippet_provider
 546                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 547                 .unwrap();
 548
 549             let comment_end = match self.inner.peek() {
 550                 Some(..) => {
 551                     let mut block_open_index = post_snippet.find("/*");
 552                     // check if it really is a block comment (and not `//*` or a nested comment)
 553                     if let Some(i) = block_open_index {
 554                         match post_snippet.find('/') {
 555                             Some(j) if j < i => block_open_index = None,
 556                             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 557                             _ => (),
 558                         }
 559                     }
 560                     let newline_index = post_snippet.find('\n');
 561                     if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
 562                         match (block_open_index, newline_index) {
 563                             // Separator before comment, with the next item on same line.
 564                             // Comment belongs to next item.
 565                             (Some(i), None) if i > separator_index => separator_index + 1,
 566                             // Block-style post-comment before the separator.
 567                             (Some(i), None) => cmp::max(
 568                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 569                                 separator_index + 1,
 570                             ),
 571                             // Block-style post-comment. Either before or after the separator.
 572                             (Some(i), Some(j)) if i < j => cmp::max(
 573                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 574                                 separator_index + 1,
 575                             ),
 576                             // Potential *single* line comment.
 577                             (_, Some(j)) if j > separator_index => j + 1,
 578                             _ => post_snippet.len(),
 579                         }
 580                     } else if let Some(newline_index) = newline_index {
 581                         // Match arms may not have trailing comma. In any case, for match arms,
 582                         // we will assume that the post comment belongs to the next arm if they
 583                         // do not end with trailing comma.
 584                         newline_index + 1
 585                     } else {
 586                         0
 587                     }
 588                 }
 589                 None => post_snippet
 590                     .find_uncommented(self.terminator)
 591                     .unwrap_or_else(|| post_snippet.len()),
 592             };
 593
 594             if !post_snippet.is_empty() && comment_end > 0 {
 595                 // Account for extra whitespace between items. This is fiddly
 596                 // because of the way we divide pre- and post- comments.
 597
 598                 // Everything from the separator to the next item.
 599                 let test_snippet = &post_snippet[comment_end - 1..];
 600                 let first_newline = test_snippet
 601                     .find('\n')
 602                     .unwrap_or_else(|| test_snippet.len());
 603                 // From the end of the first line of comments.
 604                 let test_snippet = &test_snippet[first_newline..];
 605                 let first = test_snippet
 606                     .find(|c: char| !c.is_whitespace())
 607                     .unwrap_or_else(|| test_snippet.len());
 608                 // From the end of the first line of comments to the next non-whitespace char.
 609                 let test_snippet = &test_snippet[..first];
 610
 611                 if count_newlines(test_snippet) > 1 {
 612                     // There were multiple line breaks which got trimmed to nothing.
 613                     new_lines = true;
 614                 }
 615             }
 616
 617             // Cleanup post-comment: strip separators and whitespace.
 618             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 619             let post_snippet = post_snippet[..comment_end].trim();
 620
 621             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 622                 post_snippet[1..].trim_matches(white_space)
 623             } else if post_snippet.starts_with(self.separator) {
 624                 post_snippet[self.separator.len()..].trim_matches(white_space)
 625             } else if post_snippet.ends_with(',') {
 626                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 627             } else {
 628                 post_snippet
 629             };
 630
 631             let post_comment = if !post_snippet_trimmed.is_empty() {
 632                 Some(post_snippet_trimmed.to_owned())
 633             } else {
 634                 None
 635             };
 636
 637             ListItem {
 638                 pre_comment,
 639                 pre_comment_style,
 640                 item: if self.inner.peek().is_none() && self.leave_last {
 641                     None
 642                 } else {
 643                     (self.get_item_string)(&item)
 644                 },
 645                 post_comment,
 646                 new_lines,
 647             }
 648         })
 649     }
 650 }
 651
 652 #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 653 // Creates an iterator over a list's items with associated comments.
 654 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 655     snippet_provider: &'a SnippetProvider,
 656     inner: I,
 657     terminator: &'a str,
 658     separator: &'a str,
 659     get_lo: F1,
 660     get_hi: F2,
 661     get_item_string: F3,
 662     prev_span_end: BytePos,
 663     next_span_start: BytePos,
 664     leave_last: bool,
 665 ) -> ListItems<'a, I, F1, F2, F3>
 666 where
 667     I: Iterator<Item = T>,
 668     F1: Fn(&T) -> BytePos,
 669     F2: Fn(&T) -> BytePos,
 670     F3: Fn(&T) -> Option<String>,
 671 {
 672     ListItems {
 673         snippet_provider,
 674         inner: inner.peekable(),
 675         get_lo,
 676         get_hi,
 677         get_item_string,
 678         prev_span_end,
 679         next_span_start,
 680         terminator,
 681         separator,
 682         leave_last,
 683     }
 684 }
 685
 686 /// Returns the count and total width of the list items.
 687 fn calculate_width<I, T>(items: I) -> (usize, usize)
 688 where
 689     I: IntoIterator<Item = T>,
 690     T: AsRef<ListItem>,
 691 {
 692     items
 693         .into_iter()
 694         .map(|item| total_item_width(item.as_ref()))
 695         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 696 }
 697
 698 pub fn total_item_width(item: &ListItem) -> usize {
 699     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 700         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 701         + item.item.as_ref().map_or(0, |str| str.len())
 702 }
 703
 704 fn comment_len(comment: Option<&str>) -> usize {
 705     match comment {
 706         Some(s) => {
 707             let text_len = s.trim().len();
 708             if text_len > 0 {
 709                 // We'll put " /*" before and " */" after inline comments.
 710                 text_len + 6
 711             } else {
 712                 text_len
 713             }
 714         }
 715         None => 0,
 716     }
 717 }
 718
 719 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 720 pub fn struct_lit_shape(
 721     shape: Shape,
 722     context: &RewriteContext,
 723     prefix_width: usize,
 724     suffix_width: usize,
 725 ) -> Option<(Option<Shape>, Shape)> {
 726     let v_shape = match context.config.indent_style() {
 727         IndentStyle::Visual => shape
 728             .visual_indent(0)
 729             .shrink_left(prefix_width)?
 730             .sub_width(suffix_width)?,
 731         IndentStyle::Block => {
 732             let shape = shape.block_indent(context.config.tab_spaces());
 733             Shape {
 734                 width: context.budget(shape.indent.width()),
 735                 ..shape
 736             }
 737         }
 738     };
 739     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 740     if let Some(w) = shape_width {
 741         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 742         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 743     } else {
 744         Some((None, v_shape))
 745     }
 746 }
 747
 748 // Compute the tactic for the internals of a struct-lit-like thing.
 749 pub fn struct_lit_tactic(
 750     h_shape: Option<Shape>,
 751     context: &RewriteContext,
 752     items: &[ListItem],
 753 ) -> DefinitiveListTactic {
 754     if let Some(h_shape) = h_shape {
 755         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 756             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 757             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 758             _ => ListTactic::Vertical,
 759         };
 760         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 761     } else {
 762         DefinitiveListTactic::Vertical
 763     }
 764 }
 765
 766 // Given a tactic and possible shapes for horizontal and vertical layout,
 767 // come up with the actual shape to use.
 768 pub fn shape_for_tactic(
 769     tactic: DefinitiveListTactic,
 770     h_shape: Option<Shape>,
 771     v_shape: Shape,
 772 ) -> Shape {
 773     match tactic {
 774         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 775         _ => v_shape,
 776     }
 777 }
 778
 779 // Create a ListFormatting object for formatting the internals of a
 780 // struct-lit-like thing, that is a series of fields.
 781 pub fn struct_lit_formatting<'a>(
 782     shape: Shape,
 783     tactic: DefinitiveListTactic,
 784     context: &'a RewriteContext,
 785     force_no_trailing_comma: bool,
 786 ) -> ListFormatting<'a> {
 787     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 788         && tactic == DefinitiveListTactic::Vertical;
 789     ListFormatting {
 790         tactic,
 791         separator: ",",
 792         trailing_separator: if force_no_trailing_comma {
 793             SeparatorTactic::Never
 794         } else {
 795             context.config.trailing_comma()
 796         },
 797         separator_place: SeparatorPlace::Back,
 798         shape,
 799         ends_with_newline,
 800         preserve_newline: true,
 801         config: context.config,
 802     }
 803 }