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