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::source_map::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     tactic: DefinitiveListTactic,
  28     separator: &'a str,
  29     trailing_separator: SeparatorTactic,
  30     separator_place: SeparatorPlace,
  31     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     ends_with_newline: bool,
  35     // Remove newlines between list elements for expressions.
  36     preserve_newline: bool,
  37     // Nested import lists get some special handling for the "Mixed" list type
  38     nested: bool,
  39     config: &'a Config,
  40 }
  41
  42 impl<'a> ListFormatting<'a> {
  43     pub fn new(shape: Shape, config: &'a Config) -> Self {
  44         ListFormatting {
  45             tactic: DefinitiveListTactic::Vertical,
  46             separator: ",",
  47             trailing_separator: SeparatorTactic::Never,
  48             separator_place: SeparatorPlace::Back,
  49             shape,
  50             ends_with_newline: true,
  51             preserve_newline: false,
  52             nested: false,
  53             config: config,
  54         }
  55     }
  56
  57     pub fn tactic(mut self, tactic: DefinitiveListTactic) -> Self {
  58         self.tactic = tactic;
  59         self
  60     }
  61
  62     pub fn separator(mut self, separator: &'a str) -> Self {
  63         self.separator = separator;
  64         self
  65     }
  66
  67     pub fn trailing_separator(mut self, trailing_separator: SeparatorTactic) -> Self {
  68         self.trailing_separator = trailing_separator;
  69         self
  70     }
  71
  72     pub fn separator_place(mut self, separator_place: SeparatorPlace) -> Self {
  73         self.separator_place = separator_place;
  74         self
  75     }
  76
  77     pub fn ends_with_newline(mut self, ends_with_newline: bool) -> Self {
  78         self.ends_with_newline = ends_with_newline;
  79         self
  80     }
  81
  82     pub fn preserve_newline(mut self, preserve_newline: bool) -> Self {
  83         self.preserve_newline = preserve_newline;
  84         self
  85     }
  86
  87     pub fn nested(mut self, nested: bool) -> Self {
  88         self.nested = nested;
  89         self
  90     }
  91
  92     pub fn needs_trailing_separator(&self) -> bool {
  93         match self.trailing_separator {
  94             // We always put separator in front.
  95             SeparatorTactic::Always => true,
  96             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
  97             SeparatorTactic::Never => {
  98                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
  99             }
 100         }
 101     }
 102 }
 103
 104 impl AsRef<ListItem> for ListItem {
 105     fn as_ref(&self) -> &ListItem {
 106         self
 107     }
 108 }
 109
 110 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
 111 pub enum ListItemCommentStyle {
 112     // Try to keep the comment on the same line with the item.
 113     SameLine,
 114     // Put the comment on the previous or the next line of the item.
 115     DifferentLine,
 116     // No comment available.
 117     None,
 118 }
 119
 120 #[derive(Debug, Clone)]
 121 pub struct ListItem {
 122     // None for comments mean that they are not present.
 123     pub pre_comment: Option<String>,
 124     pub pre_comment_style: ListItemCommentStyle,
 125     // Item should include attributes and doc comments. None indicates a failed
 126     // rewrite.
 127     pub item: Option<String>,
 128     pub post_comment: Option<String>,
 129     // Whether there is extra whitespace before this item.
 130     pub new_lines: bool,
 131 }
 132
 133 impl ListItem {
 134     pub fn empty() -> ListItem {
 135         ListItem {
 136             pre_comment: None,
 137             pre_comment_style: ListItemCommentStyle::None,
 138             item: None,
 139             post_comment: None,
 140             new_lines: false,
 141         }
 142     }
 143
 144     pub fn inner_as_ref(&self) -> &str {
 145         self.item.as_ref().map_or("", |s| s)
 146     }
 147
 148     pub fn is_different_group(&self) -> bool {
 149         self.inner_as_ref().contains('\n') || self.pre_comment.is_some() || self
 150             .post_comment
 151             .as_ref()
 152             .map_or(false, |s| s.contains('\n'))
 153     }
 154
 155     pub fn is_multiline(&self) -> bool {
 156         self.inner_as_ref().contains('\n')
 157             || self
 158                 .pre_comment
 159                 .as_ref()
 160                 .map_or(false, |s| s.contains('\n'))
 161             || self
 162                 .post_comment
 163                 .as_ref()
 164                 .map_or(false, |s| s.contains('\n'))
 165     }
 166
 167     pub fn has_single_line_comment(&self) -> bool {
 168         self.pre_comment
 169             .as_ref()
 170             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 171             || self
 172                 .post_comment
 173                 .as_ref()
 174                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 175     }
 176
 177     pub fn has_comment(&self) -> bool {
 178         self.pre_comment.is_some() || self.post_comment.is_some()
 179     }
 180
 181     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 182         ListItem {
 183             pre_comment: None,
 184             pre_comment_style: ListItemCommentStyle::None,
 185             item: Some(s.into()),
 186             post_comment: None,
 187             new_lines: false,
 188         }
 189     }
 190
 191     // true if the item causes something to be written.
 192     fn is_substantial(&self) -> bool {
 193         fn empty(s: &Option<String>) -> bool {
 194             match *s {
 195                 Some(ref s) if !s.is_empty() => false,
 196                 _ => true,
 197             }
 198         }
 199
 200         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 201     }
 202 }
 203
 204 /// The type of separator for lists.
 205 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 206 pub enum Separator {
 207     Comma,
 208     VerticalBar,
 209 }
 210
 211 impl Separator {
 212     pub fn len(self) -> usize {
 213         match self {
 214             // 2 = `, `
 215             Separator::Comma => 2,
 216             // 3 = ` | `
 217             Separator::VerticalBar => 3,
 218         }
 219     }
 220 }
 221
 222 pub fn definitive_tactic<I, T>(
 223     items: I,
 224     tactic: ListTactic,
 225     sep: Separator,
 226     width: usize,
 227 ) -> DefinitiveListTactic
 228 where
 229     I: IntoIterator<Item = T> + Clone,
 230     T: AsRef<ListItem>,
 231 {
 232     let pre_line_comments = items
 233         .clone()
 234         .into_iter()
 235         .any(|item| item.as_ref().has_single_line_comment());
 236
 237     let limit = match tactic {
 238         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 239         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 240         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 241         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 242         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 243     };
 244
 245     let (sep_count, total_width) = calculate_width(items.clone());
 246     let total_sep_len = sep.len() * sep_count.saturating_sub(1);
 247     let real_total = total_width + total_sep_len;
 248
 249     if real_total <= limit
 250         && !pre_line_comments
 251         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 252     {
 253         DefinitiveListTactic::Horizontal
 254     } else {
 255         match tactic {
 256             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 257             _ => DefinitiveListTactic::Vertical,
 258         }
 259     }
 260 }
 261
 262 // Format a list of commented items into a string.
 263 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 264 where
 265     I: IntoIterator<Item = T> + Clone,
 266     T: AsRef<ListItem>,
 267 {
 268     let tactic = formatting.tactic;
 269     let sep_len = formatting.separator.len();
 270
 271     // Now that we know how we will layout, we can decide for sure if there
 272     // will be a trailing separator.
 273     let mut trailing_separator = formatting.needs_trailing_separator();
 274     let mut result = String::with_capacity(128);
 275     let cloned_items = items.clone();
 276     let mut iter = items.into_iter().enumerate().peekable();
 277     let mut item_max_width: Option<usize> = None;
 278     let sep_place =
 279         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 280     let mut prev_item_had_post_comment = false;
 281     let mut prev_item_is_nested_import = false;
 282
 283     let mut line_len = 0;
 284     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 285     while let Some((i, item)) = iter.next() {
 286         let item = item.as_ref();
 287         let inner_item = item.item.as_ref()?;
 288         let first = i == 0;
 289         let last = iter.peek().is_none();
 290         let mut separate = match sep_place {
 291             SeparatorPlace::Front => !first,
 292             SeparatorPlace::Back => !last || trailing_separator,
 293         };
 294         let item_sep_len = if separate { sep_len } else { 0 };
 295
 296         // Item string may be multi-line. Its length (used for block comment alignment)
 297         // should be only the length of the last line.
 298         let item_last_line = if item.is_multiline() {
 299             inner_item.lines().last().unwrap_or("")
 300         } else {
 301             inner_item.as_ref()
 302         };
 303         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 304         if item_last_line.starts_with(&**indent_str) {
 305             item_last_line_width -= indent_str.len();
 306         }
 307
 308         if !item.is_substantial() {
 309             continue;
 310         }
 311
 312         match tactic {
 313             DefinitiveListTactic::Horizontal if !first => {
 314                 result.push(' ');
 315             }
 316             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 317                 if i == 0 {
 318                     // Nothing
 319                 } else if i < num_args_before {
 320                     result.push(' ');
 321                 } else if i <= num_args_before + 1 {
 322                     result.push('\n');
 323                     result.push_str(indent_str);
 324                 } else {
 325                     result.push(' ');
 326                 }
 327             }
 328             DefinitiveListTactic::Vertical
 329                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 330             {
 331                 result.push('\n');
 332                 result.push_str(indent_str);
 333             }
 334             DefinitiveListTactic::Mixed => {
 335                 let total_width = total_item_width(item) + item_sep_len;
 336
 337                 // 1 is space between separator and item.
 338                 if (line_len > 0 && line_len + 1 + total_width > formatting.shape.width)
 339                     || prev_item_had_post_comment
 340                     || (formatting.nested
 341                         && (prev_item_is_nested_import || (!first && inner_item.contains("::"))))
 342                 {
 343                     result.push('\n');
 344                     result.push_str(indent_str);
 345                     line_len = 0;
 346                     if formatting.ends_with_newline {
 347                         trailing_separator = true;
 348                     }
 349                 } else if line_len > 0 {
 350                     result.push(' ');
 351                     line_len += 1;
 352                 }
 353
 354                 if last && formatting.ends_with_newline {
 355                     separate = formatting.trailing_separator != SeparatorTactic::Never;
 356                 }
 357
 358                 line_len += total_width;
 359             }
 360             _ => {}
 361         }
 362
 363         // Pre-comments
 364         if let Some(ref comment) = item.pre_comment {
 365             // Block style in non-vertical mode.
 366             let block_mode = tactic == DefinitiveListTactic::Horizontal;
 367             // Width restriction is only relevant in vertical mode.
 368             let comment =
 369                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 370             result.push_str(&comment);
 371
 372             if !inner_item.is_empty() {
 373                 if tactic == DefinitiveListTactic::Vertical || tactic == DefinitiveListTactic::Mixed
 374                 {
 375                     // We cannot keep pre-comments on the same line if the comment if normalized.
 376                     let keep_comment = if formatting.config.normalize_comments()
 377                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 378                     {
 379                         false
 380                     } else {
 381                         // We will try to keep the comment on the same line with the item here.
 382                         // 1 = ` `
 383                         let total_width = total_item_width(item) + item_sep_len + 1;
 384                         total_width <= formatting.shape.width
 385                     };
 386                     if keep_comment {
 387                         result.push(' ');
 388                     } else {
 389                         result.push('\n');
 390                         result.push_str(indent_str);
 391                         // This is the width of the item (without comments).
 392                         line_len = item.item.as_ref().map_or(0, |str| str.len());
 393                     }
 394                 } else {
 395                     result.push(' ');
 396                 }
 397             }
 398             item_max_width = None;
 399         }
 400
 401         if separate && sep_place.is_front() && !first {
 402             result.push_str(formatting.separator.trim());
 403             result.push(' ');
 404         }
 405         result.push_str(inner_item);
 406
 407         // Post-comments
 408         if tactic == DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 409             let comment = item.post_comment.as_ref().unwrap();
 410             let formatted_comment = rewrite_comment(
 411                 comment,
 412                 true,
 413                 Shape::legacy(formatting.shape.width, Indent::empty()),
 414                 formatting.config,
 415             )?;
 416
 417             result.push(' ');
 418             result.push_str(&formatted_comment);
 419         }
 420
 421         if separate && sep_place.is_back() {
 422             result.push_str(formatting.separator);
 423         }
 424
 425         if tactic != DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 426             let comment = item.post_comment.as_ref().unwrap();
 427             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 428
 429             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 430                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 431                     *item_max_width = Some(max_width_of_item_with_post_comment(
 432                         &cloned_items,
 433                         i,
 434                         overhead,
 435                         formatting.config.max_width(),
 436                     ));
 437                 }
 438                 let overhead = if starts_with_newline(comment) {
 439                     0
 440                 } else if let Some(max_width) = *item_max_width {
 441                     max_width + 2
 442                 } else {
 443                     // 1 = space between item and comment.
 444                     item_last_line_width + 1
 445                 };
 446                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 447                 let offset = formatting.shape.indent + overhead;
 448                 let comment_shape = Shape::legacy(width, offset);
 449
 450                 // Use block-style only for the last item or multiline comments.
 451                 let block_style = !formatting.ends_with_newline && last
 452                     || comment.trim().contains('\n')
 453                     || comment.trim().len() > width;
 454
 455                 rewrite_comment(
 456                     comment.trim_left(),
 457                     block_style,
 458                     comment_shape,
 459                     formatting.config,
 460                 )
 461             };
 462
 463             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 464
 465             if !starts_with_newline(comment) {
 466                 let mut comment_alignment =
 467                     post_comment_alignment(item_max_width, inner_item.len());
 468                 if first_line_width(&formatted_comment)
 469                     + last_line_width(&result)
 470                     + comment_alignment
 471                     + 1
 472                     > formatting.config.max_width()
 473                 {
 474                     item_max_width = None;
 475                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 476                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 477                 }
 478                 for _ in 0..=comment_alignment {
 479                     result.push(' ');
 480                 }
 481                 // An additional space for the missing trailing separator.
 482                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 483                 {
 484                     result.push(' ');
 485                 }
 486             } else {
 487                 result.push('\n');
 488                 result.push_str(indent_str);
 489             }
 490             if formatted_comment.contains('\n') {
 491                 item_max_width = None;
 492             }
 493             result.push_str(&formatted_comment);
 494         } else {
 495             item_max_width = None;
 496         }
 497
 498         if formatting.preserve_newline
 499             && !last
 500             && tactic == DefinitiveListTactic::Vertical
 501             && item.new_lines
 502         {
 503             item_max_width = None;
 504             result.push('\n');
 505         }
 506
 507         prev_item_had_post_comment = item.post_comment.is_some();
 508         prev_item_is_nested_import = inner_item.contains("::");
 509     }
 510
 511     Some(result)
 512 }
 513
 514 fn max_width_of_item_with_post_comment<I, T>(
 515     items: &I,
 516     i: usize,
 517     overhead: usize,
 518     max_budget: usize,
 519 ) -> usize
 520 where
 521     I: IntoIterator<Item = T> + Clone,
 522     T: AsRef<ListItem>,
 523 {
 524     let mut max_width = 0;
 525     let mut first = true;
 526     for item in items.clone().into_iter().skip(i) {
 527         let item = item.as_ref();
 528         let inner_item_width = item.inner_as_ref().len();
 529         if !first
 530             && (item.is_different_group()
 531                 || item.post_comment.is_none()
 532                 || inner_item_width + overhead > max_budget)
 533         {
 534             return max_width;
 535         }
 536         if max_width < inner_item_width {
 537             max_width = inner_item_width;
 538         }
 539         if item.new_lines {
 540             return max_width;
 541         }
 542         first = false;
 543     }
 544     max_width
 545 }
 546
 547 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 548     item_max_width.unwrap_or(0).saturating_sub(inner_item_len)
 549 }
 550
 551 pub struct ListItems<'a, I, F1, F2, F3>
 552 where
 553     I: Iterator,
 554 {
 555     snippet_provider: &'a SnippetProvider<'a>,
 556     inner: Peekable<I>,
 557     get_lo: F1,
 558     get_hi: F2,
 559     get_item_string: F3,
 560     prev_span_end: BytePos,
 561     next_span_start: BytePos,
 562     terminator: &'a str,
 563     separator: &'a str,
 564     leave_last: bool,
 565 }
 566
 567 pub fn extract_pre_comment(pre_snippet: &str) -> (Option<String>, ListItemCommentStyle) {
 568     let trimmed_pre_snippet = pre_snippet.trim();
 569     let has_block_comment = trimmed_pre_snippet.ends_with("*/");
 570     let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 571     if has_block_comment {
 572         let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 573         if pre_snippet
 574             .chars()
 575             .rev()
 576             .take(comment_end + 1)
 577             .any(|c| c == '\n')
 578         {
 579             (
 580                 Some(trimmed_pre_snippet.to_owned()),
 581                 ListItemCommentStyle::DifferentLine,
 582             )
 583         } else {
 584             (
 585                 Some(trimmed_pre_snippet.to_owned()),
 586                 ListItemCommentStyle::SameLine,
 587             )
 588         }
 589     } else if has_single_line_comment {
 590         (
 591             Some(trimmed_pre_snippet.to_owned()),
 592             ListItemCommentStyle::DifferentLine,
 593         )
 594     } else {
 595         (None, ListItemCommentStyle::None)
 596     }
 597 }
 598
 599 pub fn extract_post_comment(
 600     post_snippet: &str,
 601     comment_end: usize,
 602     separator: &str,
 603 ) -> Option<String> {
 604     let white_space: &[_] = &[' ', '\t'];
 605
 606     // Cleanup post-comment: strip separators and whitespace.
 607     let post_snippet = post_snippet[..comment_end].trim();
 608     let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 609         post_snippet[1..].trim_matches(white_space)
 610     } else if post_snippet.starts_with(separator) {
 611         post_snippet[separator.len()..].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     if !post_snippet_trimmed.is_empty() {
 619         Some(post_snippet_trimmed.to_owned())
 620     } else {
 621         None
 622     }
 623 }
 624
 625 pub fn get_comment_end(
 626     post_snippet: &str,
 627     separator: &str,
 628     terminator: &str,
 629     is_last: bool,
 630 ) -> usize {
 631     if is_last {
 632         return post_snippet
 633             .find_uncommented(terminator)
 634             .unwrap_or_else(|| post_snippet.len());
 635     }
 636
 637     let mut block_open_index = post_snippet.find("/*");
 638     // check if it really is a block comment (and not `//*` or a nested comment)
 639     if let Some(i) = block_open_index {
 640         match post_snippet.find('/') {
 641             Some(j) if j < i => block_open_index = None,
 642             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 643             _ => (),
 644         }
 645     }
 646     let newline_index = post_snippet.find('\n');
 647     if let Some(separator_index) = post_snippet.find_uncommented(separator) {
 648         match (block_open_index, newline_index) {
 649             // Separator before comment, with the next item on same line.
 650             // Comment belongs to next item.
 651             (Some(i), None) if i > separator_index => separator_index + 1,
 652             // Block-style post-comment before the separator.
 653             (Some(i), None) => cmp::max(
 654                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 655                 separator_index + 1,
 656             ),
 657             // Block-style post-comment. Either before or after the separator.
 658             (Some(i), Some(j)) if i < j => cmp::max(
 659                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 660                 separator_index + 1,
 661             ),
 662             // Potential *single* line comment.
 663             (_, Some(j)) if j > separator_index => j + 1,
 664             _ => post_snippet.len(),
 665         }
 666     } else if let Some(newline_index) = newline_index {
 667         // Match arms may not have trailing comma. In any case, for match arms,
 668         // we will assume that the post comment belongs to the next arm if they
 669         // do not end with trailing comma.
 670         newline_index + 1
 671     } else {
 672         0
 673     }
 674 }
 675
 676 // Account for extra whitespace between items. This is fiddly
 677 // because of the way we divide pre- and post- comments.
 678 fn has_extra_newline(post_snippet: &str, comment_end: usize) -> bool {
 679     if post_snippet.is_empty() || comment_end == 0 {
 680         return false;
 681     }
 682
 683     // Everything from the separator to the next item.
 684     let test_snippet = &post_snippet[comment_end - 1..];
 685     let first_newline = test_snippet
 686         .find('\n')
 687         .unwrap_or_else(|| test_snippet.len());
 688     // From the end of the first line of comments.
 689     let test_snippet = &test_snippet[first_newline..];
 690     let first = test_snippet
 691         .find(|c: char| !c.is_whitespace())
 692         .unwrap_or_else(|| test_snippet.len());
 693     // From the end of the first line of comments to the next non-whitespace char.
 694     let test_snippet = &test_snippet[..first];
 695
 696     // There were multiple line breaks which got trimmed to nothing.
 697     count_newlines(test_snippet) > 1
 698 }
 699
 700 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 701 where
 702     I: Iterator<Item = T>,
 703     F1: Fn(&T) -> BytePos,
 704     F2: Fn(&T) -> BytePos,
 705     F3: Fn(&T) -> Option<String>,
 706 {
 707     type Item = ListItem;
 708
 709     fn next(&mut self) -> Option<Self::Item> {
 710         self.inner.next().map(|item| {
 711             // Pre-comment
 712             let pre_snippet = self
 713                 .snippet_provider
 714                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 715                 .unwrap_or("");
 716             let (pre_comment, pre_comment_style) = extract_pre_comment(pre_snippet);
 717
 718             // Post-comment
 719             let next_start = match self.inner.peek() {
 720                 Some(next_item) => (self.get_lo)(next_item),
 721                 None => self.next_span_start,
 722             };
 723             let post_snippet = self
 724                 .snippet_provider
 725                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 726                 .unwrap_or("");
 727             let comment_end = get_comment_end(
 728                 post_snippet,
 729                 self.separator,
 730                 self.terminator,
 731                 self.inner.peek().is_none(),
 732             );
 733             let new_lines = has_extra_newline(post_snippet, comment_end);
 734             let post_comment = extract_post_comment(post_snippet, comment_end, self.separator);
 735
 736             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 737
 738             ListItem {
 739                 pre_comment,
 740                 pre_comment_style,
 741                 item: if self.inner.peek().is_none() && self.leave_last {
 742                     None
 743                 } else {
 744                     (self.get_item_string)(&item)
 745                 },
 746                 post_comment,
 747                 new_lines,
 748             }
 749         })
 750     }
 751 }
 752
 753 #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 754 // Creates an iterator over a list's items with associated comments.
 755 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 756     snippet_provider: &'a SnippetProvider,
 757     inner: I,
 758     terminator: &'a str,
 759     separator: &'a str,
 760     get_lo: F1,
 761     get_hi: F2,
 762     get_item_string: F3,
 763     prev_span_end: BytePos,
 764     next_span_start: BytePos,
 765     leave_last: bool,
 766 ) -> ListItems<'a, I, F1, F2, F3>
 767 where
 768     I: Iterator<Item = T>,
 769     F1: Fn(&T) -> BytePos,
 770     F2: Fn(&T) -> BytePos,
 771     F3: Fn(&T) -> Option<String>,
 772 {
 773     ListItems {
 774         snippet_provider,
 775         inner: inner.peekable(),
 776         get_lo,
 777         get_hi,
 778         get_item_string,
 779         prev_span_end,
 780         next_span_start,
 781         terminator,
 782         separator,
 783         leave_last,
 784     }
 785 }
 786
 787 /// Returns the count and total width of the list items.
 788 fn calculate_width<I, T>(items: I) -> (usize, usize)
 789 where
 790     I: IntoIterator<Item = T>,
 791     T: AsRef<ListItem>,
 792 {
 793     items
 794         .into_iter()
 795         .map(|item| total_item_width(item.as_ref()))
 796         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 797 }
 798
 799 pub fn total_item_width(item: &ListItem) -> usize {
 800     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 801         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 802         + item.item.as_ref().map_or(0, |str| str.len())
 803 }
 804
 805 fn comment_len(comment: Option<&str>) -> usize {
 806     match comment {
 807         Some(s) => {
 808             let text_len = s.trim().len();
 809             if text_len > 0 {
 810                 // We'll put " /*" before and " */" after inline comments.
 811                 text_len + 6
 812             } else {
 813                 text_len
 814             }
 815         }
 816         None => 0,
 817     }
 818 }
 819
 820 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 821 pub fn struct_lit_shape(
 822     shape: Shape,
 823     context: &RewriteContext,
 824     prefix_width: usize,
 825     suffix_width: usize,
 826 ) -> Option<(Option<Shape>, Shape)> {
 827     let v_shape = match context.config.indent_style() {
 828         IndentStyle::Visual => shape
 829             .visual_indent(0)
 830             .shrink_left(prefix_width)?
 831             .sub_width(suffix_width)?,
 832         IndentStyle::Block => {
 833             let shape = shape.block_indent(context.config.tab_spaces());
 834             Shape {
 835                 width: context.budget(shape.indent.width()),
 836                 ..shape
 837             }
 838         }
 839     };
 840     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 841     if let Some(w) = shape_width {
 842         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 843         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 844     } else {
 845         Some((None, v_shape))
 846     }
 847 }
 848
 849 // Compute the tactic for the internals of a struct-lit-like thing.
 850 pub fn struct_lit_tactic(
 851     h_shape: Option<Shape>,
 852     context: &RewriteContext,
 853     items: &[ListItem],
 854 ) -> DefinitiveListTactic {
 855     if let Some(h_shape) = h_shape {
 856         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 857             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 858             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 859             _ => ListTactic::Vertical,
 860         };
 861         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 862     } else {
 863         DefinitiveListTactic::Vertical
 864     }
 865 }
 866
 867 // Given a tactic and possible shapes for horizontal and vertical layout,
 868 // come up with the actual shape to use.
 869 pub fn shape_for_tactic(
 870     tactic: DefinitiveListTactic,
 871     h_shape: Option<Shape>,
 872     v_shape: Shape,
 873 ) -> Shape {
 874     match tactic {
 875         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 876         _ => v_shape,
 877     }
 878 }
 879
 880 // Create a ListFormatting object for formatting the internals of a
 881 // struct-lit-like thing, that is a series of fields.
 882 pub fn struct_lit_formatting<'a>(
 883     shape: Shape,
 884     tactic: DefinitiveListTactic,
 885     context: &'a RewriteContext,
 886     force_no_trailing_comma: bool,
 887 ) -> ListFormatting<'a> {
 888     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 889         && tactic == DefinitiveListTactic::Vertical;
 890     ListFormatting {
 891         tactic,
 892         separator: ",",
 893         trailing_separator: if force_no_trailing_comma {
 894             SeparatorTactic::Never
 895         } else {
 896             context.config.trailing_comma()
 897         },
 898         separator_place: SeparatorPlace::Back,
 899         shape,
 900         ends_with_newline,
 901         preserve_newline: true,
 902         nested: false,
 903         config: context.config,
 904     }
 905 }