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