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