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     // Whether comments should be visually aligned.
  40     align_comments: bool,
  41     config: &'a Config,
  42 }
  43
  44 impl<'a> ListFormatting<'a> {
  45     pub fn new(shape: Shape, config: &'a Config) -> Self {
  46         ListFormatting {
  47             tactic: DefinitiveListTactic::Vertical,
  48             separator: ",",
  49             trailing_separator: SeparatorTactic::Never,
  50             separator_place: SeparatorPlace::Back,
  51             shape,
  52             ends_with_newline: true,
  53             preserve_newline: false,
  54             nested: false,
  55             align_comments: true,
  56             config,
  57         }
  58     }
  59
  60     pub fn tactic(mut self, tactic: DefinitiveListTactic) -> Self {
  61         self.tactic = tactic;
  62         self
  63     }
  64
  65     pub fn separator(mut self, separator: &'a str) -> Self {
  66         self.separator = separator;
  67         self
  68     }
  69
  70     pub fn trailing_separator(mut self, trailing_separator: SeparatorTactic) -> Self {
  71         self.trailing_separator = trailing_separator;
  72         self
  73     }
  74
  75     pub fn separator_place(mut self, separator_place: SeparatorPlace) -> Self {
  76         self.separator_place = separator_place;
  77         self
  78     }
  79
  80     pub fn ends_with_newline(mut self, ends_with_newline: bool) -> Self {
  81         self.ends_with_newline = ends_with_newline;
  82         self
  83     }
  84
  85     pub fn preserve_newline(mut self, preserve_newline: bool) -> Self {
  86         self.preserve_newline = preserve_newline;
  87         self
  88     }
  89
  90     pub fn nested(mut self, nested: bool) -> Self {
  91         self.nested = nested;
  92         self
  93     }
  94
  95     pub fn align_comments(mut self, align_comments: bool) -> Self {
  96         self.align_comments = align_comments;
  97         self
  98     }
  99
 100     pub fn needs_trailing_separator(&self) -> bool {
 101         match self.trailing_separator {
 102             // We always put separator in front.
 103             SeparatorTactic::Always => true,
 104             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
 105             SeparatorTactic::Never => {
 106                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
 107             }
 108         }
 109     }
 110 }
 111
 112 impl AsRef<ListItem> for ListItem {
 113     fn as_ref(&self) -> &ListItem {
 114         self
 115     }
 116 }
 117
 118 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
 119 pub enum ListItemCommentStyle {
 120     // Try to keep the comment on the same line with the item.
 121     SameLine,
 122     // Put the comment on the previous or the next line of the item.
 123     DifferentLine,
 124     // No comment available.
 125     None,
 126 }
 127
 128 #[derive(Debug, Clone)]
 129 pub struct ListItem {
 130     // None for comments mean that they are not present.
 131     pub pre_comment: Option<String>,
 132     pub pre_comment_style: ListItemCommentStyle,
 133     // Item should include attributes and doc comments. None indicates a failed
 134     // rewrite.
 135     pub item: Option<String>,
 136     pub post_comment: Option<String>,
 137     // Whether there is extra whitespace before this item.
 138     pub new_lines: bool,
 139 }
 140
 141 impl ListItem {
 142     pub fn empty() -> ListItem {
 143         ListItem {
 144             pre_comment: None,
 145             pre_comment_style: ListItemCommentStyle::None,
 146             item: None,
 147             post_comment: None,
 148             new_lines: false,
 149         }
 150     }
 151
 152     pub fn inner_as_ref(&self) -> &str {
 153         self.item.as_ref().map_or("", |s| s)
 154     }
 155
 156     pub fn is_different_group(&self) -> bool {
 157         self.inner_as_ref().contains('\n')
 158             || self.pre_comment.is_some()
 159             || self
 160                 .post_comment
 161                 .as_ref()
 162                 .map_or(false, |s| s.contains('\n'))
 163     }
 164
 165     pub fn is_multiline(&self) -> bool {
 166         self.inner_as_ref().contains('\n')
 167             || self
 168                 .pre_comment
 169                 .as_ref()
 170                 .map_or(false, |s| s.contains('\n'))
 171             || self
 172                 .post_comment
 173                 .as_ref()
 174                 .map_or(false, |s| s.contains('\n'))
 175     }
 176
 177     pub fn has_single_line_comment(&self) -> bool {
 178         self.pre_comment
 179             .as_ref()
 180             .map_or(false, |comment| comment.trim_start().starts_with("//"))
 181             || self
 182                 .post_comment
 183                 .as_ref()
 184                 .map_or(false, |comment| comment.trim_start().starts_with("//"))
 185     }
 186
 187     pub fn has_comment(&self) -> bool {
 188         self.pre_comment.is_some() || self.post_comment.is_some()
 189     }
 190
 191     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 192         ListItem {
 193             pre_comment: None,
 194             pre_comment_style: ListItemCommentStyle::None,
 195             item: Some(s.into()),
 196             post_comment: None,
 197             new_lines: false,
 198         }
 199     }
 200
 201     // true if the item causes something to be written.
 202     fn is_substantial(&self) -> bool {
 203         fn empty(s: &Option<String>) -> bool {
 204             match *s {
 205                 Some(ref s) if !s.is_empty() => false,
 206                 _ => true,
 207             }
 208         }
 209
 210         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 211     }
 212 }
 213
 214 /// The type of separator for lists.
 215 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 216 pub enum Separator {
 217     Comma,
 218     VerticalBar,
 219 }
 220
 221 impl Separator {
 222     pub fn len(self) -> usize {
 223         match self {
 224             // 2 = `, `
 225             Separator::Comma => 2,
 226             // 3 = ` | `
 227             Separator::VerticalBar => 3,
 228         }
 229     }
 230 }
 231
 232 pub fn definitive_tactic<I, T>(
 233     items: I,
 234     tactic: ListTactic,
 235     sep: Separator,
 236     width: usize,
 237 ) -> DefinitiveListTactic
 238 where
 239     I: IntoIterator<Item = T> + Clone,
 240     T: AsRef<ListItem>,
 241 {
 242     let pre_line_comments = items
 243         .clone()
 244         .into_iter()
 245         .any(|item| item.as_ref().has_single_line_comment());
 246
 247     let limit = match tactic {
 248         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 249         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 250         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 251         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 252         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 253     };
 254
 255     let (sep_count, total_width) = calculate_width(items.clone());
 256     let total_sep_len = sep.len() * sep_count.saturating_sub(1);
 257     let real_total = total_width + total_sep_len;
 258
 259     if real_total <= limit
 260         && !pre_line_comments
 261         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 262     {
 263         DefinitiveListTactic::Horizontal
 264     } else {
 265         match tactic {
 266             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 267             _ => DefinitiveListTactic::Vertical,
 268         }
 269     }
 270 }
 271
 272 // Format a list of commented items into a string.
 273 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 274 where
 275     I: IntoIterator<Item = T> + Clone,
 276     T: AsRef<ListItem>,
 277 {
 278     let tactic = formatting.tactic;
 279     let sep_len = formatting.separator.len();
 280
 281     // Now that we know how we will layout, we can decide for sure if there
 282     // will be a trailing separator.
 283     let mut trailing_separator = formatting.needs_trailing_separator();
 284     let mut result = String::with_capacity(128);
 285     let cloned_items = items.clone();
 286     let mut iter = items.into_iter().enumerate().peekable();
 287     let mut item_max_width: Option<usize> = None;
 288     let sep_place =
 289         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 290     let mut prev_item_had_post_comment = false;
 291     let mut prev_item_is_nested_import = false;
 292
 293     let mut line_len = 0;
 294     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 295     while let Some((i, item)) = iter.next() {
 296         let item = item.as_ref();
 297         let inner_item = item.item.as_ref()?;
 298         let first = i == 0;
 299         let last = iter.peek().is_none();
 300         let mut separate = match sep_place {
 301             SeparatorPlace::Front => !first,
 302             SeparatorPlace::Back => !last || trailing_separator,
 303         };
 304         let item_sep_len = if separate { sep_len } else { 0 };
 305
 306         // Item string may be multi-line. Its length (used for block comment alignment)
 307         // should be only the length of the last line.
 308         let item_last_line = if item.is_multiline() {
 309             inner_item.lines().last().unwrap_or("")
 310         } else {
 311             inner_item.as_ref()
 312         };
 313         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 314         if item_last_line.starts_with(&**indent_str) {
 315             item_last_line_width -= indent_str.len();
 316         }
 317
 318         if !item.is_substantial() {
 319             continue;
 320         }
 321
 322         match tactic {
 323             DefinitiveListTactic::Horizontal if !first => {
 324                 result.push(' ');
 325             }
 326             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 327                 if i == 0 {
 328                     // Nothing
 329                 } else if i < num_args_before {
 330                     result.push(' ');
 331                 } else if i <= num_args_before + 1 {
 332                     result.push('\n');
 333                     result.push_str(indent_str);
 334                 } else {
 335                     result.push(' ');
 336                 }
 337             }
 338             DefinitiveListTactic::Vertical
 339                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 340             {
 341                 result.push('\n');
 342                 result.push_str(indent_str);
 343             }
 344             DefinitiveListTactic::Mixed => {
 345                 let total_width = total_item_width(item) + item_sep_len;
 346
 347                 // 1 is space between separator and item.
 348                 if (line_len > 0 && line_len + 1 + total_width > formatting.shape.width)
 349                     || prev_item_had_post_comment
 350                     || (formatting.nested
 351                         && (prev_item_is_nested_import || (!first && inner_item.contains("::"))))
 352                 {
 353                     result.push('\n');
 354                     result.push_str(indent_str);
 355                     line_len = 0;
 356                     if formatting.ends_with_newline {
 357                         trailing_separator = true;
 358                     }
 359                 } else if line_len > 0 {
 360                     result.push(' ');
 361                     line_len += 1;
 362                 }
 363
 364                 if last && formatting.ends_with_newline {
 365                     separate = formatting.trailing_separator != SeparatorTactic::Never;
 366                 }
 367
 368                 line_len += total_width;
 369             }
 370             _ => {}
 371         }
 372
 373         // Pre-comments
 374         if let Some(ref comment) = item.pre_comment {
 375             // Block style in non-vertical mode.
 376             let block_mode = tactic == DefinitiveListTactic::Horizontal;
 377             // Width restriction is only relevant in vertical mode.
 378             let comment =
 379                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 380             result.push_str(&comment);
 381
 382             if !inner_item.is_empty() {
 383                 if tactic == DefinitiveListTactic::Vertical || tactic == DefinitiveListTactic::Mixed
 384                 {
 385                     // We cannot keep pre-comments on the same line if the comment if normalized.
 386                     let keep_comment = if formatting.config.normalize_comments()
 387                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 388                     {
 389                         false
 390                     } else {
 391                         // We will try to keep the comment on the same line with the item here.
 392                         // 1 = ` `
 393                         let total_width = total_item_width(item) + item_sep_len + 1;
 394                         total_width <= formatting.shape.width
 395                     };
 396                     if keep_comment {
 397                         result.push(' ');
 398                     } else {
 399                         result.push('\n');
 400                         result.push_str(indent_str);
 401                         // This is the width of the item (without comments).
 402                         line_len = item.item.as_ref().map_or(0, |str| str.len());
 403                     }
 404                 } else {
 405                     result.push(' ');
 406                 }
 407             }
 408             item_max_width = None;
 409         }
 410
 411         if separate && sep_place.is_front() && !first {
 412             result.push_str(formatting.separator.trim());
 413             result.push(' ');
 414         }
 415         result.push_str(inner_item);
 416
 417         // Post-comments
 418         if tactic == DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 419             let comment = item.post_comment.as_ref().unwrap();
 420             let formatted_comment = rewrite_comment(
 421                 comment,
 422                 true,
 423                 Shape::legacy(formatting.shape.width, Indent::empty()),
 424                 formatting.config,
 425             )?;
 426
 427             result.push(' ');
 428             result.push_str(&formatted_comment);
 429         }
 430
 431         if separate && sep_place.is_back() {
 432             result.push_str(formatting.separator);
 433         }
 434
 435         if tactic != DefinitiveListTactic::Horizontal && item.post_comment.is_some() {
 436             let comment = item.post_comment.as_ref().unwrap();
 437             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 438
 439             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 440                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 441                     *item_max_width = Some(max_width_of_item_with_post_comment(
 442                         &cloned_items,
 443                         i,
 444                         overhead,
 445                         formatting.config.max_width(),
 446                     ));
 447                 }
 448                 let overhead = if starts_with_newline(comment) {
 449                     0
 450                 } else if let Some(max_width) = *item_max_width {
 451                     max_width + 2
 452                 } else {
 453                     // 1 = space between item and comment.
 454                     item_last_line_width + 1
 455                 };
 456                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 457                 let offset = formatting.shape.indent + overhead;
 458                 let comment_shape = Shape::legacy(width, offset);
 459
 460                 // Use block-style only for the last item or multiline comments.
 461                 let block_style = !formatting.ends_with_newline && last
 462                     || comment.trim().contains('\n')
 463                     || comment.trim().len() > width;
 464
 465                 rewrite_comment(
 466                     comment.trim_start(),
 467                     block_style,
 468                     comment_shape,
 469                     formatting.config,
 470                 )
 471             };
 472
 473             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 474
 475             if !starts_with_newline(comment) {
 476                 if formatting.align_comments {
 477                     let mut comment_alignment =
 478                         post_comment_alignment(item_max_width, inner_item.len());
 479                     if first_line_width(&formatted_comment)
 480                         + last_line_width(&result)
 481                         + comment_alignment
 482                         + 1
 483                         > formatting.config.max_width()
 484                     {
 485                         item_max_width = None;
 486                         formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 487                         comment_alignment =
 488                             post_comment_alignment(item_max_width, inner_item.len());
 489                     }
 490                     for _ in 0..=comment_alignment {
 491                         result.push(' ');
 492                     }
 493                 }
 494                 // An additional space for the missing trailing separator (or
 495                 // if we skipped alignment above).
 496                 if !formatting.align_comments
 497                     || (last
 498                         && item_max_width.is_some()
 499                         && !separate
 500                         && !formatting.separator.is_empty())
 501                 {
 502                     result.push(' ');
 503                 }
 504             } else {
 505                 result.push('\n');
 506                 result.push_str(indent_str);
 507             }
 508             if formatted_comment.contains('\n') {
 509                 item_max_width = None;
 510             }
 511             result.push_str(&formatted_comment);
 512         } else {
 513             item_max_width = None;
 514         }
 515
 516         if formatting.preserve_newline
 517             && !last
 518             && tactic == DefinitiveListTactic::Vertical
 519             && item.new_lines
 520         {
 521             item_max_width = None;
 522             result.push('\n');
 523         }
 524
 525         prev_item_had_post_comment = item.post_comment.is_some();
 526         prev_item_is_nested_import = inner_item.contains("::");
 527     }
 528
 529     Some(result)
 530 }
 531
 532 fn max_width_of_item_with_post_comment<I, T>(
 533     items: &I,
 534     i: usize,
 535     overhead: usize,
 536     max_budget: usize,
 537 ) -> usize
 538 where
 539     I: IntoIterator<Item = T> + Clone,
 540     T: AsRef<ListItem>,
 541 {
 542     let mut max_width = 0;
 543     let mut first = true;
 544     for item in items.clone().into_iter().skip(i) {
 545         let item = item.as_ref();
 546         let inner_item_width = item.inner_as_ref().len();
 547         if !first
 548             && (item.is_different_group()
 549                 || item.post_comment.is_none()
 550                 || inner_item_width + overhead > max_budget)
 551         {
 552             return max_width;
 553         }
 554         if max_width < inner_item_width {
 555             max_width = inner_item_width;
 556         }
 557         if item.new_lines {
 558             return max_width;
 559         }
 560         first = false;
 561     }
 562     max_width
 563 }
 564
 565 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 566     item_max_width.unwrap_or(0).saturating_sub(inner_item_len)
 567 }
 568
 569 pub struct ListItems<'a, I, F1, F2, F3>
 570 where
 571     I: Iterator,
 572 {
 573     snippet_provider: &'a SnippetProvider<'a>,
 574     inner: Peekable<I>,
 575     get_lo: F1,
 576     get_hi: F2,
 577     get_item_string: F3,
 578     prev_span_end: BytePos,
 579     next_span_start: BytePos,
 580     terminator: &'a str,
 581     separator: &'a str,
 582     leave_last: bool,
 583 }
 584
 585 pub fn extract_pre_comment(pre_snippet: &str) -> (Option<String>, ListItemCommentStyle) {
 586     let trimmed_pre_snippet = pre_snippet.trim();
 587     let has_block_comment = trimmed_pre_snippet.ends_with("*/");
 588     let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 589     if has_block_comment {
 590         let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 591         if pre_snippet
 592             .chars()
 593             .rev()
 594             .take(comment_end + 1)
 595             .any(|c| c == '\n')
 596         {
 597             (
 598                 Some(trimmed_pre_snippet.to_owned()),
 599                 ListItemCommentStyle::DifferentLine,
 600             )
 601         } else {
 602             (
 603                 Some(trimmed_pre_snippet.to_owned()),
 604                 ListItemCommentStyle::SameLine,
 605             )
 606         }
 607     } else if has_single_line_comment {
 608         (
 609             Some(trimmed_pre_snippet.to_owned()),
 610             ListItemCommentStyle::DifferentLine,
 611         )
 612     } else {
 613         (None, ListItemCommentStyle::None)
 614     }
 615 }
 616
 617 pub fn extract_post_comment(
 618     post_snippet: &str,
 619     comment_end: usize,
 620     separator: &str,
 621 ) -> Option<String> {
 622     let white_space: &[_] = &[' ', '\t'];
 623
 624     // Cleanup post-comment: strip separators and whitespace.
 625     let post_snippet = post_snippet[..comment_end].trim();
 626     let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 627         post_snippet[1..].trim_matches(white_space)
 628     } else if post_snippet.starts_with(separator) {
 629         post_snippet[separator.len()..].trim_matches(white_space)
 630     } else if post_snippet.ends_with(',') {
 631         post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 632     } else {
 633         post_snippet
 634     };
 635
 636     if !post_snippet_trimmed.is_empty() {
 637         Some(post_snippet_trimmed.to_owned())
 638     } else {
 639         None
 640     }
 641 }
 642
 643 pub fn get_comment_end(
 644     post_snippet: &str,
 645     separator: &str,
 646     terminator: &str,
 647     is_last: bool,
 648 ) -> usize {
 649     if is_last {
 650         return post_snippet
 651             .find_uncommented(terminator)
 652             .unwrap_or_else(|| post_snippet.len());
 653     }
 654
 655     let mut block_open_index = post_snippet.find("/*");
 656     // check if it really is a block comment (and not `//*` or a nested comment)
 657     if let Some(i) = block_open_index {
 658         match post_snippet.find('/') {
 659             Some(j) if j < i => block_open_index = None,
 660             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 661             _ => (),
 662         }
 663     }
 664     let newline_index = post_snippet.find('\n');
 665     if let Some(separator_index) = post_snippet.find_uncommented(separator) {
 666         match (block_open_index, newline_index) {
 667             // Separator before comment, with the next item on same line.
 668             // Comment belongs to next item.
 669             (Some(i), None) if i > separator_index => separator_index + 1,
 670             // Block-style post-comment before the separator.
 671             (Some(i), None) => cmp::max(
 672                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 673                 separator_index + 1,
 674             ),
 675             // Block-style post-comment. Either before or after the separator.
 676             (Some(i), Some(j)) if i < j => cmp::max(
 677                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 678                 separator_index + 1,
 679             ),
 680             // Potential *single* line comment.
 681             (_, Some(j)) if j > separator_index => j + 1,
 682             _ => post_snippet.len(),
 683         }
 684     } else if let Some(newline_index) = newline_index {
 685         // Match arms may not have trailing comma. In any case, for match arms,
 686         // we will assume that the post comment belongs to the next arm if they
 687         // do not end with trailing comma.
 688         newline_index + 1
 689     } else {
 690         0
 691     }
 692 }
 693
 694 // Account for extra whitespace between items. This is fiddly
 695 // because of the way we divide pre- and post- comments.
 696 fn has_extra_newline(post_snippet: &str, comment_end: usize) -> bool {
 697     if post_snippet.is_empty() || comment_end == 0 {
 698         return false;
 699     }
 700
 701     // Everything from the separator to the next item.
 702     let test_snippet = &post_snippet[comment_end - 1..];
 703     let first_newline = test_snippet
 704         .find('\n')
 705         .unwrap_or_else(|| test_snippet.len());
 706     // From the end of the first line of comments.
 707     let test_snippet = &test_snippet[first_newline..];
 708     let first = test_snippet
 709         .find(|c: char| !c.is_whitespace())
 710         .unwrap_or_else(|| test_snippet.len());
 711     // From the end of the first line of comments to the next non-whitespace char.
 712     let test_snippet = &test_snippet[..first];
 713
 714     // There were multiple line breaks which got trimmed to nothing.
 715     count_newlines(test_snippet) > 1
 716 }
 717
 718 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 719 where
 720     I: Iterator<Item = T>,
 721     F1: Fn(&T) -> BytePos,
 722     F2: Fn(&T) -> BytePos,
 723     F3: Fn(&T) -> Option<String>,
 724 {
 725     type Item = ListItem;
 726
 727     fn next(&mut self) -> Option<Self::Item> {
 728         self.inner.next().map(|item| {
 729             // Pre-comment
 730             let pre_snippet = self
 731                 .snippet_provider
 732                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 733                 .unwrap_or("");
 734             let (pre_comment, pre_comment_style) = extract_pre_comment(pre_snippet);
 735
 736             // Post-comment
 737             let next_start = match self.inner.peek() {
 738                 Some(next_item) => (self.get_lo)(next_item),
 739                 None => self.next_span_start,
 740             };
 741             let post_snippet = self
 742                 .snippet_provider
 743                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 744                 .unwrap_or("");
 745             let comment_end = get_comment_end(
 746                 post_snippet,
 747                 self.separator,
 748                 self.terminator,
 749                 self.inner.peek().is_none(),
 750             );
 751             let new_lines = has_extra_newline(post_snippet, comment_end);
 752             let post_comment = extract_post_comment(post_snippet, comment_end, self.separator);
 753
 754             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 755
 756             ListItem {
 757                 pre_comment,
 758                 pre_comment_style,
 759                 item: if self.inner.peek().is_none() && self.leave_last {
 760                     None
 761                 } else {
 762                     (self.get_item_string)(&item)
 763                 },
 764                 post_comment,
 765                 new_lines,
 766             }
 767         })
 768     }
 769 }
 770
 771 #[allow(clippy::too_many_arguments)]
 772 // Creates an iterator over a list's items with associated comments.
 773 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 774     snippet_provider: &'a SnippetProvider,
 775     inner: I,
 776     terminator: &'a str,
 777     separator: &'a str,
 778     get_lo: F1,
 779     get_hi: F2,
 780     get_item_string: F3,
 781     prev_span_end: BytePos,
 782     next_span_start: BytePos,
 783     leave_last: bool,
 784 ) -> ListItems<'a, I, F1, F2, F3>
 785 where
 786     I: Iterator<Item = T>,
 787     F1: Fn(&T) -> BytePos,
 788     F2: Fn(&T) -> BytePos,
 789     F3: Fn(&T) -> Option<String>,
 790 {
 791     ListItems {
 792         snippet_provider,
 793         inner: inner.peekable(),
 794         get_lo,
 795         get_hi,
 796         get_item_string,
 797         prev_span_end,
 798         next_span_start,
 799         terminator,
 800         separator,
 801         leave_last,
 802     }
 803 }
 804
 805 /// Returns the count and total width of the list items.
 806 fn calculate_width<I, T>(items: I) -> (usize, usize)
 807 where
 808     I: IntoIterator<Item = T>,
 809     T: AsRef<ListItem>,
 810 {
 811     items
 812         .into_iter()
 813         .map(|item| total_item_width(item.as_ref()))
 814         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 815 }
 816
 817 pub fn total_item_width(item: &ListItem) -> usize {
 818     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 819         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 820         + item.item.as_ref().map_or(0, |str| str.len())
 821 }
 822
 823 fn comment_len(comment: Option<&str>) -> usize {
 824     match comment {
 825         Some(s) => {
 826             let text_len = s.trim().len();
 827             if text_len > 0 {
 828                 // We'll put " /*" before and " */" after inline comments.
 829                 text_len + 6
 830             } else {
 831                 text_len
 832             }
 833         }
 834         None => 0,
 835     }
 836 }
 837
 838 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 839 pub fn struct_lit_shape(
 840     shape: Shape,
 841     context: &RewriteContext,
 842     prefix_width: usize,
 843     suffix_width: usize,
 844 ) -> Option<(Option<Shape>, Shape)> {
 845     let v_shape = match context.config.indent_style() {
 846         IndentStyle::Visual => shape
 847             .visual_indent(0)
 848             .shrink_left(prefix_width)?
 849             .sub_width(suffix_width)?,
 850         IndentStyle::Block => {
 851             let shape = shape.block_indent(context.config.tab_spaces());
 852             Shape {
 853                 width: context.budget(shape.indent.width()),
 854                 ..shape
 855             }
 856         }
 857     };
 858     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 859     if let Some(w) = shape_width {
 860         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 861         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 862     } else {
 863         Some((None, v_shape))
 864     }
 865 }
 866
 867 // Compute the tactic for the internals of a struct-lit-like thing.
 868 pub fn struct_lit_tactic(
 869     h_shape: Option<Shape>,
 870     context: &RewriteContext,
 871     items: &[ListItem],
 872 ) -> DefinitiveListTactic {
 873     if let Some(h_shape) = h_shape {
 874         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 875             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 876             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 877             _ => ListTactic::Vertical,
 878         };
 879         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 880     } else {
 881         DefinitiveListTactic::Vertical
 882     }
 883 }
 884
 885 // Given a tactic and possible shapes for horizontal and vertical layout,
 886 // come up with the actual shape to use.
 887 pub fn shape_for_tactic(
 888     tactic: DefinitiveListTactic,
 889     h_shape: Option<Shape>,
 890     v_shape: Shape,
 891 ) -> Shape {
 892     match tactic {
 893         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 894         _ => v_shape,
 895     }
 896 }
 897
 898 // Create a ListFormatting object for formatting the internals of a
 899 // struct-lit-like thing, that is a series of fields.
 900 pub fn struct_lit_formatting<'a>(
 901     shape: Shape,
 902     tactic: DefinitiveListTactic,
 903     context: &'a RewriteContext,
 904     force_no_trailing_comma: bool,
 905 ) -> ListFormatting<'a> {
 906     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 907         && tactic == DefinitiveListTactic::Vertical;
 908     ListFormatting {
 909         tactic,
 910         separator: ",",
 911         trailing_separator: if force_no_trailing_comma {
 912             SeparatorTactic::Never
 913         } else {
 914             context.config.trailing_comma()
 915         },
 916         separator_place: SeparatorPlace::Back,
 917         shape,
 918         ends_with_newline,
 919         preserve_newline: true,
 920         nested: false,
 921         align_comments: true,
 922         config: context.config,
 923     }
 924 }