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