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