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 empty() -> ListItem {
  84         ListItem {
  85             pre_comment: None,
  86             pre_comment_style: ListItemCommentStyle::None,
  87             item: None,
  88             post_comment: None,
  89             new_lines: false,
  90         }
  91     }
  92
  93     pub fn inner_as_ref(&self) -> &str {
  94         self.item.as_ref().map_or("", |s| s)
  95     }
  96
  97     pub fn is_different_group(&self) -> bool {
  98         self.inner_as_ref().contains('\n') || self.pre_comment.is_some()
  99             || self.post_comment
 100                 .as_ref()
 101                 .map_or(false, |s| s.contains('\n'))
 102     }
 103
 104     pub fn is_multiline(&self) -> bool {
 105         self.inner_as_ref().contains('\n')
 106             || self.pre_comment
 107                 .as_ref()
 108                 .map_or(false, |s| s.contains('\n'))
 109             || self.post_comment
 110                 .as_ref()
 111                 .map_or(false, |s| s.contains('\n'))
 112     }
 113
 114     pub fn has_single_line_comment(&self) -> bool {
 115         self.pre_comment
 116             .as_ref()
 117             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 118             || self.post_comment
 119                 .as_ref()
 120                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 121     }
 122
 123     pub fn has_comment(&self) -> bool {
 124         self.pre_comment.is_some() || self.post_comment.is_some()
 125     }
 126
 127     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 128         ListItem {
 129             pre_comment: None,
 130             pre_comment_style: ListItemCommentStyle::None,
 131             item: Some(s.into()),
 132             post_comment: None,
 133             new_lines: false,
 134         }
 135     }
 136
 137     // true if the item causes something to be written.
 138     fn is_substantial(&self) -> bool {
 139         fn empty(s: &Option<String>) -> bool {
 140             match *s {
 141                 Some(ref s) if !s.is_empty() => false,
 142                 _ => true,
 143             }
 144         }
 145
 146         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 147     }
 148 }
 149
 150 /// The type of separator for lists.
 151 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 152 pub enum Separator {
 153     Comma,
 154     VerticalBar,
 155 }
 156
 157 impl Separator {
 158     pub fn len(&self) -> usize {
 159         match *self {
 160             // 2 = `, `
 161             Separator::Comma => 2,
 162             // 3 = ` | `
 163             Separator::VerticalBar => 3,
 164         }
 165     }
 166 }
 167
 168 pub fn definitive_tactic<I, T>(
 169     items: I,
 170     tactic: ListTactic,
 171     sep: Separator,
 172     width: usize,
 173 ) -> DefinitiveListTactic
 174 where
 175     I: IntoIterator<Item = T> + Clone,
 176     T: AsRef<ListItem>,
 177 {
 178     let pre_line_comments = items
 179         .clone()
 180         .into_iter()
 181         .any(|item| item.as_ref().has_single_line_comment());
 182
 183     let limit = match tactic {
 184         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 185         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 186         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 187         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 188         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 189     };
 190
 191     let (sep_count, total_width) = calculate_width(items.clone());
 192     let total_sep_len = sep.len() * sep_count.checked_sub(1).unwrap_or(0);
 193     let real_total = total_width + total_sep_len;
 194
 195     if real_total <= limit && !pre_line_comments
 196         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 197     {
 198         DefinitiveListTactic::Horizontal
 199     } else {
 200         match tactic {
 201             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 202             _ => DefinitiveListTactic::Vertical,
 203         }
 204     }
 205 }
 206
 207 // Format a list of commented items into a string.
 208 // TODO: add unit tests
 209 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 210 where
 211     I: IntoIterator<Item = T> + Clone,
 212     T: AsRef<ListItem>,
 213 {
 214     let tactic = formatting.tactic;
 215     let sep_len = formatting.separator.len();
 216
 217     // Now that we know how we will layout, we can decide for sure if there
 218     // will be a trailing separator.
 219     let mut trailing_separator = formatting.needs_trailing_separator();
 220     let mut result = String::with_capacity(128);
 221     let cloned_items = items.clone();
 222     let mut iter = items.into_iter().enumerate().peekable();
 223     let mut item_max_width: Option<usize> = None;
 224     let sep_place =
 225         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 226
 227     let mut line_len = 0;
 228     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 229     while let Some((i, item)) = iter.next() {
 230         let item = item.as_ref();
 231         let inner_item = item.item.as_ref()?;
 232         let first = i == 0;
 233         let last = iter.peek().is_none();
 234         let mut separate = match sep_place {
 235             SeparatorPlace::Front => !first,
 236             SeparatorPlace::Back => !last || trailing_separator,
 237         };
 238         let item_sep_len = if separate { sep_len } else { 0 };
 239
 240         // Item string may be multi-line. Its length (used for block comment alignment)
 241         // should be only the length of the last line.
 242         let item_last_line = if item.is_multiline() {
 243             inner_item.lines().last().unwrap_or("")
 244         } else {
 245             inner_item.as_ref()
 246         };
 247         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 248         if item_last_line.starts_with(&**indent_str) {
 249             item_last_line_width -= indent_str.len();
 250         }
 251
 252         if !item.is_substantial() {
 253             continue;
 254         }
 255
 256         match tactic {
 257             DefinitiveListTactic::Horizontal if !first => {
 258                 result.push(' ');
 259             }
 260             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 261                 if i == 0 {
 262                     // Nothing
 263                 } else if i < num_args_before {
 264                     result.push(' ');
 265                 } else if i <= num_args_before + 1 {
 266                     result.push('\n');
 267                     result.push_str(indent_str);
 268                 } else {
 269                     result.push(' ');
 270                 }
 271             }
 272             DefinitiveListTactic::Vertical
 273                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 274             {
 275                 result.push('\n');
 276                 result.push_str(indent_str);
 277             }
 278             DefinitiveListTactic::Mixed => {
 279                 let total_width = total_item_width(item) + item_sep_len;
 280
 281                 // 1 is space between separator and item.
 282                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 283                     result.push('\n');
 284                     result.push_str(indent_str);
 285                     line_len = 0;
 286                     if formatting.ends_with_newline {
 287                         trailing_separator = true;
 288                     }
 289                 }
 290
 291                 if last && formatting.ends_with_newline {
 292                     separate = formatting.trailing_separator != SeparatorTactic::Never;
 293                 }
 294
 295                 if line_len > 0 {
 296                     result.push(' ');
 297                     line_len += 1;
 298                 }
 299
 300                 line_len += total_width;
 301             }
 302             _ => {}
 303         }
 304
 305         // Pre-comments
 306         if let Some(ref comment) = item.pre_comment {
 307             // Block style in non-vertical mode.
 308             let block_mode = tactic != DefinitiveListTactic::Vertical;
 309             // Width restriction is only relevant in vertical mode.
 310             let comment =
 311                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 312             result.push_str(&comment);
 313
 314             if !inner_item.is_empty() {
 315                 if tactic == DefinitiveListTactic::Vertical {
 316                     // We cannot keep pre-comments on the same line if the comment if normalized.
 317                     let keep_comment = if formatting.config.normalize_comments()
 318                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 319                     {
 320                         false
 321                     } else {
 322                         // We will try to keep the comment on the same line with the item here.
 323                         // 1 = ` `
 324                         let total_width = total_item_width(item) + item_sep_len + 1;
 325                         total_width <= formatting.shape.width
 326                     };
 327                     if keep_comment {
 328                         result.push(' ');
 329                     } else {
 330                         result.push('\n');
 331                         result.push_str(indent_str);
 332                     }
 333                 } else {
 334                     result.push(' ');
 335                 }
 336             }
 337             item_max_width = None;
 338         }
 339
 340         if separate && sep_place.is_front() && !first {
 341             result.push_str(formatting.separator.trim());
 342             result.push(' ');
 343         }
 344         result.push_str(inner_item);
 345
 346         // Post-comments
 347         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 348             let comment = item.post_comment.as_ref().unwrap();
 349             let formatted_comment = rewrite_comment(
 350                 comment,
 351                 true,
 352                 Shape::legacy(formatting.shape.width, Indent::empty()),
 353                 formatting.config,
 354             )?;
 355
 356             result.push(' ');
 357             result.push_str(&formatted_comment);
 358         }
 359
 360         if separate && sep_place.is_back() {
 361             result.push_str(formatting.separator);
 362         }
 363
 364         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 365             let comment = item.post_comment.as_ref().unwrap();
 366             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 367
 368             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 369                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 370                     *item_max_width = Some(max_width_of_item_with_post_comment(
 371                         &cloned_items,
 372                         i,
 373                         overhead,
 374                         formatting.config.max_width(),
 375                     ));
 376                 }
 377                 let overhead = if starts_with_newline(comment) {
 378                     0
 379                 } else if let Some(max_width) = *item_max_width {
 380                     max_width + 2
 381                 } else {
 382                     // 1 = space between item and comment.
 383                     item_last_line_width + 1
 384                 };
 385                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 386                 let offset = formatting.shape.indent + overhead;
 387                 let comment_shape = Shape::legacy(width, offset);
 388
 389                 // Use block-style only for the last item or multiline comments.
 390                 let block_style = !formatting.ends_with_newline && last
 391                     || comment.trim().contains('\n')
 392                     || comment.trim().len() > width;
 393
 394                 rewrite_comment(
 395                     comment.trim_left(),
 396                     block_style,
 397                     comment_shape,
 398                     formatting.config,
 399                 )
 400             };
 401
 402             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 403
 404             if !starts_with_newline(comment) {
 405                 let mut comment_alignment =
 406                     post_comment_alignment(item_max_width, inner_item.len());
 407                 if first_line_width(&formatted_comment) + last_line_width(&result)
 408                     + comment_alignment + 1 > formatting.config.max_width()
 409                 {
 410                     item_max_width = None;
 411                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 412                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 413                 }
 414                 for _ in 0..(comment_alignment + 1) {
 415                     result.push(' ');
 416                 }
 417                 // An additional space for the missing trailing separator.
 418                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 419                 {
 420                     result.push(' ');
 421                 }
 422             } else {
 423                 result.push('\n');
 424                 result.push_str(indent_str);
 425             }
 426             if formatted_comment.contains('\n') {
 427                 item_max_width = None;
 428             }
 429             result.push_str(&formatted_comment);
 430         } else {
 431             item_max_width = None;
 432         }
 433
 434         if formatting.preserve_newline && !last && tactic == DefinitiveListTactic::Vertical
 435             && item.new_lines
 436         {
 437             item_max_width = None;
 438             result.push('\n');
 439         }
 440     }
 441
 442     Some(result)
 443 }
 444
 445 fn max_width_of_item_with_post_comment<I, T>(
 446     items: &I,
 447     i: usize,
 448     overhead: usize,
 449     max_budget: usize,
 450 ) -> usize
 451 where
 452     I: IntoIterator<Item = T> + Clone,
 453     T: AsRef<ListItem>,
 454 {
 455     let mut max_width = 0;
 456     let mut first = true;
 457     for item in items.clone().into_iter().skip(i) {
 458         let item = item.as_ref();
 459         let inner_item_width = item.inner_as_ref().len();
 460         if !first
 461             && (item.is_different_group() || !item.post_comment.is_some()
 462                 || inner_item_width + overhead > max_budget)
 463         {
 464             return max_width;
 465         }
 466         if max_width < inner_item_width {
 467             max_width = inner_item_width;
 468         }
 469         if item.new_lines {
 470             return max_width;
 471         }
 472         first = false;
 473     }
 474     max_width
 475 }
 476
 477 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 478     item_max_width
 479         .and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
 480         .unwrap_or(0)
 481 }
 482
 483 pub struct ListItems<'a, I, F1, F2, F3>
 484 where
 485     I: Iterator,
 486 {
 487     snippet_provider: &'a SnippetProvider<'a>,
 488     inner: Peekable<I>,
 489     get_lo: F1,
 490     get_hi: F2,
 491     get_item_string: F3,
 492     prev_span_end: BytePos,
 493     next_span_start: BytePos,
 494     terminator: &'a str,
 495     separator: &'a str,
 496     leave_last: bool,
 497 }
 498
 499 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 500 where
 501     I: Iterator<Item = T>,
 502     F1: Fn(&T) -> BytePos,
 503     F2: Fn(&T) -> BytePos,
 504     F3: Fn(&T) -> Option<String>,
 505 {
 506     type Item = ListItem;
 507
 508     fn next(&mut self) -> Option<Self::Item> {
 509         let white_space: &[_] = &[' ', '\t'];
 510
 511         self.inner.next().map(|item| {
 512             let mut new_lines = false;
 513             // Pre-comment
 514             let pre_snippet = self.snippet_provider
 515                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 516                 .unwrap();
 517             let trimmed_pre_snippet = pre_snippet.trim();
 518             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 519             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 520             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 521                 (
 522                     Some(trimmed_pre_snippet.to_owned()),
 523                     ListItemCommentStyle::DifferentLine,
 524                 )
 525             } else if has_block_comment {
 526                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 527                 if pre_snippet
 528                     .chars()
 529                     .rev()
 530                     .take(comment_end + 1)
 531                     .any(|c| c == '\n')
 532                 {
 533                     (
 534                         Some(trimmed_pre_snippet.to_owned()),
 535                         ListItemCommentStyle::DifferentLine,
 536                     )
 537                 } else {
 538                     (
 539                         Some(trimmed_pre_snippet.to_owned()),
 540                         ListItemCommentStyle::SameLine,
 541                     )
 542                 }
 543             } else {
 544                 (None, ListItemCommentStyle::None)
 545             };
 546
 547             // Post-comment
 548             let next_start = match self.inner.peek() {
 549                 Some(next_item) => (self.get_lo)(next_item),
 550                 None => self.next_span_start,
 551             };
 552             let post_snippet = self.snippet_provider
 553                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 554                 .unwrap();
 555
 556             let comment_end = match self.inner.peek() {
 557                 Some(..) => {
 558                     let mut block_open_index = post_snippet.find("/*");
 559                     // check if it really is a block comment (and not `//*` or a nested comment)
 560                     if let Some(i) = block_open_index {
 561                         match post_snippet.find('/') {
 562                             Some(j) if j < i => block_open_index = None,
 563                             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 564                             _ => (),
 565                         }
 566                     }
 567                     let newline_index = post_snippet.find('\n');
 568                     if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
 569                         match (block_open_index, newline_index) {
 570                             // Separator before comment, with the next item on same line.
 571                             // Comment belongs to next item.
 572                             (Some(i), None) if i > separator_index => separator_index + 1,
 573                             // Block-style post-comment before the separator.
 574                             (Some(i), None) => cmp::max(
 575                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 576                                 separator_index + 1,
 577                             ),
 578                             // Block-style post-comment. Either before or after the separator.
 579                             (Some(i), Some(j)) if i < j => cmp::max(
 580                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 581                                 separator_index + 1,
 582                             ),
 583                             // Potential *single* line comment.
 584                             (_, Some(j)) if j > separator_index => j + 1,
 585                             _ => post_snippet.len(),
 586                         }
 587                     } else if let Some(newline_index) = newline_index {
 588                         // Match arms may not have trailing comma. In any case, for match arms,
 589                         // we will assume that the post comment belongs to the next arm if they
 590                         // do not end with trailing comma.
 591                         newline_index + 1
 592                     } else {
 593                         0
 594                     }
 595                 }
 596                 None => post_snippet
 597                     .find_uncommented(self.terminator)
 598                     .unwrap_or_else(|| post_snippet.len()),
 599             };
 600
 601             if !post_snippet.is_empty() && comment_end > 0 {
 602                 // Account for extra whitespace between items. This is fiddly
 603                 // because of the way we divide pre- and post- comments.
 604
 605                 // Everything from the separator to the next item.
 606                 let test_snippet = &post_snippet[comment_end - 1..];
 607                 let first_newline = test_snippet
 608                     .find('\n')
 609                     .unwrap_or_else(|| test_snippet.len());
 610                 // From the end of the first line of comments.
 611                 let test_snippet = &test_snippet[first_newline..];
 612                 let first = test_snippet
 613                     .find(|c: char| !c.is_whitespace())
 614                     .unwrap_or_else(|| test_snippet.len());
 615                 // From the end of the first line of comments to the next non-whitespace char.
 616                 let test_snippet = &test_snippet[..first];
 617
 618                 if count_newlines(test_snippet) > 1 {
 619                     // There were multiple line breaks which got trimmed to nothing.
 620                     new_lines = true;
 621                 }
 622             }
 623
 624             // Cleanup post-comment: strip separators and whitespace.
 625             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 626             let post_snippet = post_snippet[..comment_end].trim();
 627
 628             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 629                 post_snippet[1..].trim_matches(white_space)
 630             } else if post_snippet.starts_with(self.separator) {
 631                 post_snippet[self.separator.len()..].trim_matches(white_space)
 632             } else if post_snippet.ends_with(',') {
 633                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 634             } else {
 635                 post_snippet
 636             };
 637
 638             let post_comment = if !post_snippet_trimmed.is_empty() {
 639                 Some(post_snippet_trimmed.to_owned())
 640             } else {
 641                 None
 642             };
 643
 644             ListItem {
 645                 pre_comment,
 646                 pre_comment_style,
 647                 item: if self.inner.peek().is_none() && self.leave_last {
 648                     None
 649                 } else {
 650                     (self.get_item_string)(&item)
 651                 },
 652                 post_comment,
 653                 new_lines,
 654             }
 655         })
 656     }
 657 }
 658
 659 #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 660 // Creates an iterator over a list's items with associated comments.
 661 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 662     snippet_provider: &'a SnippetProvider,
 663     inner: I,
 664     terminator: &'a str,
 665     separator: &'a str,
 666     get_lo: F1,
 667     get_hi: F2,
 668     get_item_string: F3,
 669     prev_span_end: BytePos,
 670     next_span_start: BytePos,
 671     leave_last: bool,
 672 ) -> ListItems<'a, I, F1, F2, F3>
 673 where
 674     I: Iterator<Item = T>,
 675     F1: Fn(&T) -> BytePos,
 676     F2: Fn(&T) -> BytePos,
 677     F3: Fn(&T) -> Option<String>,
 678 {
 679     ListItems {
 680         snippet_provider,
 681         inner: inner.peekable(),
 682         get_lo,
 683         get_hi,
 684         get_item_string,
 685         prev_span_end,
 686         next_span_start,
 687         terminator,
 688         separator,
 689         leave_last,
 690     }
 691 }
 692
 693 /// Returns the count and total width of the list items.
 694 fn calculate_width<I, T>(items: I) -> (usize, usize)
 695 where
 696     I: IntoIterator<Item = T>,
 697     T: AsRef<ListItem>,
 698 {
 699     items
 700         .into_iter()
 701         .map(|item| total_item_width(item.as_ref()))
 702         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 703 }
 704
 705 pub fn total_item_width(item: &ListItem) -> usize {
 706     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 707         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 708         + item.item.as_ref().map_or(0, |str| str.len())
 709 }
 710
 711 fn comment_len(comment: Option<&str>) -> usize {
 712     match comment {
 713         Some(s) => {
 714             let text_len = s.trim().len();
 715             if text_len > 0 {
 716                 // We'll put " /*" before and " */" after inline comments.
 717                 text_len + 6
 718             } else {
 719                 text_len
 720             }
 721         }
 722         None => 0,
 723     }
 724 }
 725
 726 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 727 pub fn struct_lit_shape(
 728     shape: Shape,
 729     context: &RewriteContext,
 730     prefix_width: usize,
 731     suffix_width: usize,
 732 ) -> Option<(Option<Shape>, Shape)> {
 733     let v_shape = match context.config.indent_style() {
 734         IndentStyle::Visual => shape
 735             .visual_indent(0)
 736             .shrink_left(prefix_width)?
 737             .sub_width(suffix_width)?,
 738         IndentStyle::Block => {
 739             let shape = shape.block_indent(context.config.tab_spaces());
 740             Shape {
 741                 width: context.budget(shape.indent.width()),
 742                 ..shape
 743             }
 744         }
 745     };
 746     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 747     if let Some(w) = shape_width {
 748         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 749         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 750     } else {
 751         Some((None, v_shape))
 752     }
 753 }
 754
 755 // Compute the tactic for the internals of a struct-lit-like thing.
 756 pub fn struct_lit_tactic(
 757     h_shape: Option<Shape>,
 758     context: &RewriteContext,
 759     items: &[ListItem],
 760 ) -> DefinitiveListTactic {
 761     if let Some(h_shape) = h_shape {
 762         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 763             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 764             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 765             _ => ListTactic::Vertical,
 766         };
 767         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 768     } else {
 769         DefinitiveListTactic::Vertical
 770     }
 771 }
 772
 773 // Given a tactic and possible shapes for horizontal and vertical layout,
 774 // come up with the actual shape to use.
 775 pub fn shape_for_tactic(
 776     tactic: DefinitiveListTactic,
 777     h_shape: Option<Shape>,
 778     v_shape: Shape,
 779 ) -> Shape {
 780     match tactic {
 781         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 782         _ => v_shape,
 783     }
 784 }
 785
 786 // Create a ListFormatting object for formatting the internals of a
 787 // struct-lit-like thing, that is a series of fields.
 788 pub fn struct_lit_formatting<'a>(
 789     shape: Shape,
 790     tactic: DefinitiveListTactic,
 791     context: &'a RewriteContext,
 792     force_no_trailing_comma: bool,
 793 ) -> ListFormatting<'a> {
 794     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 795         && tactic == DefinitiveListTactic::Vertical;
 796     ListFormatting {
 797         tactic,
 798         separator: ",",
 799         trailing_separator: if force_no_trailing_comma {
 800             SeparatorTactic::Never
 801         } else {
 802             context.config.trailing_comma()
 803         },
 804         separator_place: SeparatorPlace::Back,
 805         shape,
 806         ends_with_newline,
 807         preserve_newline: true,
 808         config: context.config,
 809     }
 810 }