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