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