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 use std::cmp;
  12 use std::iter::Peekable;
  13
  14 use syntax::codemap::{BytePos, CodeMap};
  15
  16 use comment::{find_comment_end, rewrite_comment, FindUncommented};
  17 use config::{Config, IndentStyle};
  18 use rewrite::RewriteContext;
  19 use shape::{Indent, Shape};
  20 use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
  21
  22 /// Formatting tactic for lists. This will be cast down to a
  23 /// `DefinitiveListTactic` depending on the number and length of the items and
  24 /// their comments.
  25 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  26 pub enum ListTactic {
  27     // One item per row.
  28     Vertical,
  29     // All items on one row.
  30     Horizontal,
  31     // Try Horizontal layout, if that fails then vertical.
  32     HorizontalVertical,
  33     // HorizontalVertical with a soft limit of n characters.
  34     LimitedHorizontalVertical(usize),
  35     // Pack as many items as possible per row over (possibly) many rows.
  36     Mixed,
  37 }
  38
  39 impl_enum_serialize_and_deserialize!(ListTactic, Vertical, Horizontal, HorizontalVertical, Mixed);
  40
  41 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  42 pub enum SeparatorTactic {
  43     Always,
  44     Never,
  45     Vertical,
  46 }
  47
  48 impl_enum_serialize_and_deserialize!(SeparatorTactic, Always, Never, Vertical);
  49
  50 impl SeparatorTactic {
  51     pub fn from_bool(b: bool) -> SeparatorTactic {
  52         if b {
  53             SeparatorTactic::Always
  54         } else {
  55             SeparatorTactic::Never
  56         }
  57     }
  58 }
  59
  60 pub struct ListFormatting<'a> {
  61     pub tactic: DefinitiveListTactic,
  62     pub separator: &'a str,
  63     pub trailing_separator: SeparatorTactic,
  64     pub separator_place: SeparatorPlace,
  65     pub shape: Shape,
  66     // Non-expressions, e.g. items, will have a new line at the end of the list.
  67     // Important for comment styles.
  68     pub ends_with_newline: bool,
  69     // Remove newlines between list elements for expressions.
  70     pub preserve_newline: bool,
  71     pub config: &'a Config,
  72 }
  73
  74 impl<'a> ListFormatting<'a> {
  75     pub fn needs_trailing_separator(&self) -> bool {
  76         match self.trailing_separator {
  77             // We always put separator in front.
  78             SeparatorTactic::Always => true,
  79             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
  80             SeparatorTactic::Never => {
  81                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
  82             }
  83         }
  84     }
  85 }
  86
  87 impl AsRef<ListItem> for ListItem {
  88     fn as_ref(&self) -> &ListItem {
  89         self
  90     }
  91 }
  92
  93 #[derive(PartialEq, Eq)]
  94 pub enum ListItemCommentStyle {
  95     // Try to keep the comment on the same line with the item.
  96     SameLine,
  97     // Put the comment on the previous or the next line of the item.
  98     DifferentLine,
  99     // No comment available.
 100     None,
 101 }
 102
 103 pub struct ListItem {
 104     // None for comments mean that they are not present.
 105     pub pre_comment: Option<String>,
 106     pub pre_comment_style: ListItemCommentStyle,
 107     // Item should include attributes and doc comments. None indicates a failed
 108     // rewrite.
 109     pub item: Option<String>,
 110     pub post_comment: Option<String>,
 111     // Whether there is extra whitespace before this item.
 112     pub new_lines: bool,
 113 }
 114
 115 impl ListItem {
 116     pub fn inner_as_ref(&self) -> &str {
 117         self.item.as_ref().map_or("", |s| s)
 118     }
 119
 120     pub fn is_different_group(&self) -> bool {
 121         self.inner_as_ref().contains('\n') || self.pre_comment.is_some()
 122             || self.post_comment
 123                 .as_ref()
 124                 .map_or(false, |s| s.contains('\n'))
 125     }
 126
 127     pub fn is_multiline(&self) -> bool {
 128         self.inner_as_ref().contains('\n')
 129             || self.pre_comment
 130                 .as_ref()
 131                 .map_or(false, |s| s.contains('\n'))
 132             || self.post_comment
 133                 .as_ref()
 134                 .map_or(false, |s| s.contains('\n'))
 135     }
 136
 137     pub fn has_comment(&self) -> bool {
 138         self.pre_comment
 139             .as_ref()
 140             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 141             || self.post_comment
 142                 .as_ref()
 143                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 144     }
 145
 146     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 147         ListItem {
 148             pre_comment: None,
 149             pre_comment_style: ListItemCommentStyle::None,
 150             item: Some(s.into()),
 151             post_comment: None,
 152             new_lines: false,
 153         }
 154     }
 155 }
 156
 157 /// The definitive formatting tactic for lists.
 158 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 159 pub enum DefinitiveListTactic {
 160     Vertical,
 161     Horizontal,
 162     Mixed,
 163     /// Special case tactic for `format!()`, `write!()` style macros.
 164     SpecialMacro(usize),
 165 }
 166
 167 impl DefinitiveListTactic {
 168     pub fn ends_with_newline(&self, indent_style: IndentStyle) -> bool {
 169         match indent_style {
 170             IndentStyle::Block => *self != DefinitiveListTactic::Horizontal,
 171             IndentStyle::Visual => false,
 172         }
 173     }
 174 }
 175
 176 /// The type of separator for lists.
 177 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 178 pub enum Separator {
 179     Comma,
 180     VerticalBar,
 181 }
 182
 183 impl Separator {
 184     pub fn len(&self) -> usize {
 185         match *self {
 186             // 2 = `, `
 187             Separator::Comma => 2,
 188             // 3 = ` | `
 189             Separator::VerticalBar => 3,
 190         }
 191     }
 192 }
 193
 194 /// Where to put separator.
 195 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 196 pub enum SeparatorPlace {
 197     Front,
 198     Back,
 199 }
 200
 201 impl_enum_serialize_and_deserialize!(SeparatorPlace, Front, Back);
 202
 203 impl SeparatorPlace {
 204     pub fn is_front(&self) -> bool {
 205         *self == SeparatorPlace::Front
 206     }
 207
 208     pub fn is_back(&self) -> bool {
 209         *self == SeparatorPlace::Back
 210     }
 211
 212     pub fn from_tactic(
 213         default: SeparatorPlace,
 214         tactic: DefinitiveListTactic,
 215         sep: &str,
 216     ) -> SeparatorPlace {
 217         match tactic {
 218             DefinitiveListTactic::Vertical => default,
 219             _ => if sep == "," {
 220                 SeparatorPlace::Back
 221             } else {
 222                 default
 223             },
 224         }
 225     }
 226 }
 227
 228 pub fn definitive_tactic<I, T>(
 229     items: I,
 230     tactic: ListTactic,
 231     sep: Separator,
 232     width: usize,
 233 ) -> DefinitiveListTactic
 234 where
 235     I: IntoIterator<Item = T> + Clone,
 236     T: AsRef<ListItem>,
 237 {
 238     let pre_line_comments = items
 239         .clone()
 240         .into_iter()
 241         .any(|item| item.as_ref().has_comment());
 242
 243     let limit = match tactic {
 244         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 245         ListTactic::Mixed => return DefinitiveListTactic::Mixed,
 246         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 247         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 248         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 249         ListTactic::HorizontalVertical => width,
 250     };
 251
 252     let (sep_count, total_width) = calculate_width(items.clone());
 253     let total_sep_len = sep.len() * sep_count.checked_sub(1).unwrap_or(0);
 254     let real_total = total_width + total_sep_len;
 255
 256     if real_total <= limit && !pre_line_comments
 257         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 258     {
 259         DefinitiveListTactic::Horizontal
 260     } else {
 261         DefinitiveListTactic::Vertical
 262     }
 263 }
 264
 265 // Format a list of commented items into a string.
 266 // TODO: add unit tests
 267 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 268 where
 269     I: IntoIterator<Item = T> + Clone,
 270     T: AsRef<ListItem>,
 271 {
 272     let tactic = formatting.tactic;
 273     let sep_len = formatting.separator.len();
 274
 275     // Now that we know how we will layout, we can decide for sure if there
 276     // will be a trailing separator.
 277     let mut trailing_separator = formatting.needs_trailing_separator();
 278     let mut result = String::with_capacity(128);
 279     let cloned_items = items.clone();
 280     let mut iter = items.into_iter().enumerate().peekable();
 281     let mut item_max_width: Option<usize> = None;
 282     let sep_place =
 283         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 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         match tactic {
 311             DefinitiveListTactic::Horizontal if !first => {
 312                 result.push(' ');
 313             }
 314             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 315                 if i == 0 {
 316                     // Nothing
 317                 } else if i < num_args_before {
 318                     result.push(' ');
 319                 } else if i <= num_args_before + 1 {
 320                     result.push('\n');
 321                     result.push_str(indent_str);
 322                 } else {
 323                     result.push(' ');
 324                 }
 325             }
 326             DefinitiveListTactic::Vertical if !first => {
 327                 result.push('\n');
 328                 result.push_str(indent_str);
 329             }
 330             DefinitiveListTactic::Mixed => {
 331                 let total_width = total_item_width(item) + item_sep_len;
 332
 333                 // 1 is space between separator and item.
 334                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 335                     result.push('\n');
 336                     result.push_str(indent_str);
 337                     line_len = 0;
 338                     if formatting.ends_with_newline {
 339                         if last {
 340                             separate = true;
 341                         } else {
 342                             trailing_separator = true;
 343                         }
 344                     }
 345                 }
 346
 347                 if line_len > 0 {
 348                     result.push(' ');
 349                     line_len += 1;
 350                 }
 351
 352                 line_len += total_width;
 353             }
 354             _ => {}
 355         }
 356
 357         // Pre-comments
 358         if let Some(ref comment) = item.pre_comment {
 359             // Block style in non-vertical mode.
 360             let block_mode = tactic != DefinitiveListTactic::Vertical;
 361             // Width restriction is only relevant in vertical mode.
 362             let comment =
 363                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 364             result.push_str(&comment);
 365
 366             if tactic == DefinitiveListTactic::Vertical {
 367                 // We cannot keep pre-comments on the same line if the comment if normalized.
 368                 let keep_comment = if formatting.config.normalize_comments()
 369                     || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 370                 {
 371                     false
 372                 } else {
 373                     // We will try to keep the comment on the same line with the item here.
 374                     // 1 = ` `
 375                     let total_width = total_item_width(item) + item_sep_len + 1;
 376                     total_width <= formatting.shape.width
 377                 };
 378                 if keep_comment {
 379                     result.push(' ');
 380                 } else {
 381                     result.push('\n');
 382                     result.push_str(indent_str);
 383                 }
 384             } else {
 385                 result.push(' ');
 386             }
 387             item_max_width = None;
 388         }
 389
 390         if separate && sep_place.is_front() && !first {
 391             result.push_str(formatting.separator.trim());
 392             result.push(' ');
 393         }
 394         result.push_str(&inner_item[..]);
 395
 396         // Post-comments
 397         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 398             let comment = item.post_comment.as_ref().unwrap();
 399             let formatted_comment = rewrite_comment(
 400                 comment,
 401                 true,
 402                 Shape::legacy(formatting.shape.width, Indent::empty()),
 403                 formatting.config,
 404             )?;
 405
 406             result.push(' ');
 407             result.push_str(&formatted_comment);
 408         }
 409
 410         if separate && sep_place.is_back() {
 411             result.push_str(formatting.separator);
 412         }
 413
 414         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 415             let comment = item.post_comment.as_ref().unwrap();
 416             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 417
 418             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 419                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 420                     *item_max_width = Some(max_width_of_item_with_post_comment(
 421                         &cloned_items,
 422                         i,
 423                         overhead,
 424                         formatting.config.max_width(),
 425                     ));
 426                 }
 427                 let overhead = if starts_with_newline(comment) {
 428                     0
 429                 } else if let Some(max_width) = *item_max_width {
 430                     max_width + 2
 431                 } else {
 432                     // 1 = space between item and comment.
 433                     item_last_line_width + 1
 434                 };
 435                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 436                 let offset = formatting.shape.indent + overhead;
 437                 let comment_shape = Shape::legacy(width, offset);
 438
 439                 // Use block-style only for the last item or multiline comments.
 440                 let block_style = !formatting.ends_with_newline && last
 441                     || comment.trim().contains('\n')
 442                     || comment.trim().len() > width;
 443
 444                 rewrite_comment(
 445                     comment.trim_left(),
 446                     block_style,
 447                     comment_shape,
 448                     formatting.config,
 449                 )
 450             };
 451
 452             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 453
 454             if !starts_with_newline(comment) {
 455                 let mut comment_alignment =
 456                     post_comment_alignment(item_max_width, inner_item.len());
 457                 if first_line_width(&formatted_comment) + last_line_width(&result)
 458                     + comment_alignment + 1 > formatting.config.max_width()
 459                 {
 460                     item_max_width = None;
 461                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 462                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 463                 }
 464                 for _ in 0..(comment_alignment + 1) {
 465                     result.push(' ');
 466                 }
 467                 // An additional space for the missing trailing separator.
 468                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 469                 {
 470                     result.push(' ');
 471                 }
 472             } else {
 473                 result.push('\n');
 474                 result.push_str(indent_str);
 475             }
 476             if formatted_comment.contains('\n') {
 477                 item_max_width = None;
 478             }
 479             result.push_str(&formatted_comment);
 480         } else {
 481             item_max_width = None;
 482         }
 483
 484         if formatting.preserve_newline && !last && tactic == DefinitiveListTactic::Vertical
 485             && item.new_lines
 486         {
 487             item_max_width = None;
 488             result.push('\n');
 489         }
 490     }
 491
 492     Some(result)
 493 }
 494
 495 fn max_width_of_item_with_post_comment<I, T>(
 496     items: &I,
 497     i: usize,
 498     overhead: usize,
 499     max_budget: usize,
 500 ) -> usize
 501 where
 502     I: IntoIterator<Item = T> + Clone,
 503     T: AsRef<ListItem>,
 504 {
 505     let mut max_width = 0;
 506     let mut first = true;
 507     for item in items.clone().into_iter().skip(i) {
 508         let item = item.as_ref();
 509         let inner_item_width = item.inner_as_ref().len();
 510         if !first
 511             && (item.is_different_group() || !item.post_comment.is_some()
 512                 || inner_item_width + overhead > max_budget)
 513         {
 514             return max_width;
 515         }
 516         if max_width < inner_item_width {
 517             max_width = inner_item_width;
 518         }
 519         if item.new_lines {
 520             return max_width;
 521         }
 522         first = false;
 523     }
 524     max_width
 525 }
 526
 527 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 528     item_max_width
 529         .and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
 530         .unwrap_or(0)
 531 }
 532
 533 pub struct ListItems<'a, I, F1, F2, F3>
 534 where
 535     I: Iterator,
 536 {
 537     codemap: &'a CodeMap,
 538     inner: Peekable<I>,
 539     get_lo: F1,
 540     get_hi: F2,
 541     get_item_string: F3,
 542     prev_span_end: BytePos,
 543     next_span_start: BytePos,
 544     terminator: &'a str,
 545     separator: &'a str,
 546     leave_last: bool,
 547 }
 548
 549 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 550 where
 551     I: Iterator<Item = T>,
 552     F1: Fn(&T) -> BytePos,
 553     F2: Fn(&T) -> BytePos,
 554     F3: Fn(&T) -> Option<String>,
 555 {
 556     type Item = ListItem;
 557
 558     fn next(&mut self) -> Option<Self::Item> {
 559         let white_space: &[_] = &[' ', '\t'];
 560
 561         self.inner.next().map(|item| {
 562             let mut new_lines = false;
 563             // Pre-comment
 564             let pre_snippet = self.codemap
 565                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 566                 .unwrap();
 567             let trimmed_pre_snippet = pre_snippet.trim();
 568             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 569             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 570             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 571                 (
 572                     Some(trimmed_pre_snippet.to_owned()),
 573                     ListItemCommentStyle::DifferentLine,
 574                 )
 575             } else if has_block_comment {
 576                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 577                 if pre_snippet
 578                     .chars()
 579                     .rev()
 580                     .take(comment_end + 1)
 581                     .any(|c| c == '\n')
 582                 {
 583                     (
 584                         Some(trimmed_pre_snippet.to_owned()),
 585                         ListItemCommentStyle::DifferentLine,
 586                     )
 587                 } else {
 588                     (
 589                         Some(trimmed_pre_snippet.to_owned()),
 590                         ListItemCommentStyle::SameLine,
 591                     )
 592                 }
 593             } else {
 594                 (None, ListItemCommentStyle::None)
 595             };
 596
 597             // Post-comment
 598             let next_start = match self.inner.peek() {
 599                 Some(next_item) => (self.get_lo)(next_item),
 600                 None => self.next_span_start,
 601             };
 602             let post_snippet = self.codemap
 603                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 604                 .unwrap();
 605
 606             let comment_end = match self.inner.peek() {
 607                 Some(..) => {
 608                     let mut block_open_index = post_snippet.find("/*");
 609                     // check if it really is a block comment (and not `//*` or a nested comment)
 610                     if let Some(i) = block_open_index {
 611                         match post_snippet.find('/') {
 612                             Some(j) if j < i => block_open_index = None,
 613                             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 614                             _ => (),
 615                         }
 616                     }
 617                     let newline_index = post_snippet.find('\n');
 618                     if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
 619                         match (block_open_index, newline_index) {
 620                             // Separator before comment, with the next item on same line.
 621                             // Comment belongs to next item.
 622                             (Some(i), None) if i > separator_index => separator_index + 1,
 623                             // Block-style post-comment before the separator.
 624                             (Some(i), None) => cmp::max(
 625                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 626                                 separator_index + 1,
 627                             ),
 628                             // Block-style post-comment. Either before or after the separator.
 629                             (Some(i), Some(j)) if i < j => cmp::max(
 630                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 631                                 separator_index + 1,
 632                             ),
 633                             // Potential *single* line comment.
 634                             (_, Some(j)) if j > separator_index => j + 1,
 635                             _ => post_snippet.len(),
 636                         }
 637                     } else if let Some(newline_index) = newline_index {
 638                         // Match arms may not have trailing comma. In any case, for match arms,
 639                         // we will assume that the post comment belongs to the next arm if they
 640                         // do not end with trailing comma.
 641                         newline_index + 1
 642                     } else {
 643                         0
 644                     }
 645                 }
 646                 None => post_snippet
 647                     .find_uncommented(self.terminator)
 648                     .unwrap_or_else(|| post_snippet.len()),
 649             };
 650
 651             if !post_snippet.is_empty() && comment_end > 0 {
 652                 // Account for extra whitespace between items. This is fiddly
 653                 // because of the way we divide pre- and post- comments.
 654
 655                 // Everything from the separator to the next item.
 656                 let test_snippet = &post_snippet[comment_end - 1..];
 657                 let first_newline = test_snippet
 658                     .find('\n')
 659                     .unwrap_or_else(|| test_snippet.len());
 660                 // From the end of the first line of comments.
 661                 let test_snippet = &test_snippet[first_newline..];
 662                 let first = test_snippet
 663                     .find(|c: char| !c.is_whitespace())
 664                     .unwrap_or_else(|| test_snippet.len());
 665                 // From the end of the first line of comments to the next non-whitespace char.
 666                 let test_snippet = &test_snippet[..first];
 667
 668                 if count_newlines(test_snippet) > 1 {
 669                     // There were multiple line breaks which got trimmed to nothing.
 670                     new_lines = true;
 671                 }
 672             }
 673
 674             // Cleanup post-comment: strip separators and whitespace.
 675             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 676             let post_snippet = post_snippet[..comment_end].trim();
 677
 678             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 679                 post_snippet[1..].trim_matches(white_space)
 680             } else if post_snippet.ends_with(',') {
 681                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 682             } else {
 683                 post_snippet
 684             };
 685
 686             let post_comment = if !post_snippet_trimmed.is_empty() {
 687                 Some(post_snippet_trimmed.to_owned())
 688             } else {
 689                 None
 690             };
 691
 692             ListItem {
 693                 pre_comment: pre_comment,
 694                 pre_comment_style: pre_comment_style,
 695                 item: if self.inner.peek().is_none() && self.leave_last {
 696                     None
 697                 } else {
 698                     (self.get_item_string)(&item)
 699                 },
 700                 post_comment: post_comment,
 701                 new_lines: new_lines,
 702             }
 703         })
 704     }
 705 }
 706
 707 // Creates an iterator over a list's items with associated comments.
 708 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 709     codemap: &'a CodeMap,
 710     inner: I,
 711     terminator: &'a str,
 712     separator: &'a str,
 713     get_lo: F1,
 714     get_hi: F2,
 715     get_item_string: F3,
 716     prev_span_end: BytePos,
 717     next_span_start: BytePos,
 718     leave_last: bool,
 719 ) -> ListItems<'a, I, F1, F2, F3>
 720 where
 721     I: Iterator<Item = T>,
 722     F1: Fn(&T) -> BytePos,
 723     F2: Fn(&T) -> BytePos,
 724     F3: Fn(&T) -> Option<String>,
 725 {
 726     ListItems {
 727         codemap: codemap,
 728         inner: inner.peekable(),
 729         get_lo: get_lo,
 730         get_hi: get_hi,
 731         get_item_string: get_item_string,
 732         prev_span_end: prev_span_end,
 733         next_span_start: next_span_start,
 734         terminator: terminator,
 735         separator: separator,
 736         leave_last: leave_last,
 737     }
 738 }
 739
 740 /// Returns the count and total width of the list items.
 741 fn calculate_width<I, T>(items: I) -> (usize, usize)
 742 where
 743     I: IntoIterator<Item = T>,
 744     T: AsRef<ListItem>,
 745 {
 746     items
 747         .into_iter()
 748         .map(|item| total_item_width(item.as_ref()))
 749         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 750 }
 751
 752 pub fn total_item_width(item: &ListItem) -> usize {
 753     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 754         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 755         + item.item.as_ref().map_or(0, |str| str.len())
 756 }
 757
 758 fn comment_len(comment: Option<&str>) -> usize {
 759     match comment {
 760         Some(s) => {
 761             let text_len = s.trim().len();
 762             if text_len > 0 {
 763                 // We'll put " /*" before and " */" after inline comments.
 764                 text_len + 6
 765             } else {
 766                 text_len
 767             }
 768         }
 769         None => 0,
 770     }
 771 }
 772
 773 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 774 pub fn struct_lit_shape(
 775     shape: Shape,
 776     context: &RewriteContext,
 777     prefix_width: usize,
 778     suffix_width: usize,
 779 ) -> Option<(Option<Shape>, Shape)> {
 780     let v_shape = match context.config.indent_style() {
 781         IndentStyle::Visual => shape
 782             .visual_indent(0)
 783             .shrink_left(prefix_width)?
 784             .sub_width(suffix_width)?,
 785         IndentStyle::Block => {
 786             let shape = shape.block_indent(context.config.tab_spaces());
 787             Shape {
 788                 width: context.budget(shape.indent.width()),
 789                 ..shape
 790             }
 791         }
 792     };
 793     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 794     if let Some(w) = shape_width {
 795         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 796         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 797     } else {
 798         Some((None, v_shape))
 799     }
 800 }
 801
 802 // Compute the tactic for the internals of a struct-lit-like thing.
 803 pub fn struct_lit_tactic(
 804     h_shape: Option<Shape>,
 805     context: &RewriteContext,
 806     items: &[ListItem],
 807 ) -> DefinitiveListTactic {
 808     if let Some(h_shape) = h_shape {
 809         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 810             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 811             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 812             _ => ListTactic::Vertical,
 813         };
 814         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 815     } else {
 816         DefinitiveListTactic::Vertical
 817     }
 818 }
 819
 820 // Given a tactic and possible shapes for horizontal and vertical layout,
 821 // come up with the actual shape to use.
 822 pub fn shape_for_tactic(
 823     tactic: DefinitiveListTactic,
 824     h_shape: Option<Shape>,
 825     v_shape: Shape,
 826 ) -> Shape {
 827     match tactic {
 828         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 829         _ => v_shape,
 830     }
 831 }
 832
 833 // Create a ListFormatting object for formatting the internals of a
 834 // struct-lit-like thing, that is a series of fields.
 835 pub fn struct_lit_formatting<'a>(
 836     shape: Shape,
 837     tactic: DefinitiveListTactic,
 838     context: &'a RewriteContext,
 839     force_no_trailing_comma: bool,
 840 ) -> ListFormatting<'a> {
 841     let ends_with_newline = context.config.indent_style() != IndentStyle::Visual
 842         && tactic == DefinitiveListTactic::Vertical;
 843     ListFormatting {
 844         tactic: tactic,
 845         separator: ",",
 846         trailing_separator: if force_no_trailing_comma {
 847             SeparatorTactic::Never
 848         } else {
 849             context.config.trailing_comma()
 850         },
 851         separator_place: SeparatorPlace::Back,
 852         shape: shape,
 853         ends_with_newline: ends_with_newline,
 854         preserve_newline: true,
 855         config: context.config,
 856     }
 857 }