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 {Indent, Shape};
  17 use comment::{find_comment_end, rewrite_comment, FindUncommented};
  18 use config::{Config, IndentStyle};
  19 use rewrite::RewriteContext;
  20 use utils::{first_line_width, last_line_width, mk_sp};
  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 = try_opt!(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 = try_opt!(rewrite_comment(
 340                 comment,
 341                 block_mode,
 342                 formatting.shape,
 343                 formatting.config,
 344             ));
 345             result.push_str(&comment);
 346
 347             if tactic == DefinitiveListTactic::Vertical {
 348                 // We cannot keep pre-comments on the same line if the comment if normalized.
 349                 let keep_comment = if formatting.config.normalize_comments() ||
 350                     item.pre_comment_style == ListItemCommentStyle::DifferentLine
 351                 {
 352                     false
 353                 } else {
 354                     // We will try to keep the comment on the same line with the item here.
 355                     // 1 = ` `
 356                     let total_width = total_item_width(item) + item_sep_len + 1;
 357                     total_width <= formatting.shape.width
 358                 };
 359                 if keep_comment {
 360                     result.push(' ');
 361                 } else {
 362                     result.push('\n');
 363                     result.push_str(indent_str);
 364                 }
 365             } else {
 366                 result.push(' ');
 367             }
 368             item_max_width = None;
 369         }
 370
 371         if separate && sep_place.is_front() && !first {
 372             result.push_str(formatting.separator.trim());
 373             result.push(' ');
 374         }
 375         result.push_str(&inner_item[..]);
 376
 377         // Post-comments
 378         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 379             let comment = item.post_comment.as_ref().unwrap();
 380             let formatted_comment = try_opt!(rewrite_comment(
 381                 comment,
 382                 true,
 383                 Shape::legacy(formatting.shape.width, Indent::empty()),
 384                 formatting.config,
 385             ));
 386
 387             result.push(' ');
 388             result.push_str(&formatted_comment);
 389         }
 390
 391         if separate && sep_place.is_back() {
 392             result.push_str(formatting.separator);
 393         }
 394
 395         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 396             let comment = item.post_comment.as_ref().unwrap();
 397             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 398
 399             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 400                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 401                     *item_max_width = Some(max_width_of_item_with_post_comment(
 402                         &cloned_items,
 403                         i,
 404                         overhead,
 405                         formatting.config.max_width(),
 406                     ));
 407                 }
 408                 let overhead = if let Some(max_width) = *item_max_width {
 409                     max_width + 2
 410                 } else {
 411                     // 1 = space between item and comment.
 412                     item_last_line_width + 1
 413                 };
 414                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 415                 let offset = formatting.shape.indent + overhead;
 416                 let comment_shape = Shape::legacy(width, offset);
 417
 418                 // Use block-style only for the last item or multiline comments.
 419                 let block_style = !formatting.ends_with_newline && last ||
 420                     comment.trim().contains('\n') ||
 421                     comment.trim().len() > width;
 422
 423                 rewrite_comment(comment, block_style, comment_shape, formatting.config)
 424             };
 425
 426             let mut formatted_comment = try_opt!(rewrite_post_comment(&mut item_max_width));
 427
 428             if !formatted_comment.starts_with('\n') {
 429                 let mut comment_alignment =
 430                     post_comment_alignment(item_max_width, inner_item.len());
 431                 if first_line_width(&formatted_comment) + last_line_width(&result) +
 432                     comment_alignment + 1 > formatting.config.max_width()
 433                 {
 434                     item_max_width = None;
 435                     formatted_comment = try_opt!(rewrite_post_comment(&mut item_max_width));
 436                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 437                 }
 438                 for _ in 0..(comment_alignment + 1) {
 439                     result.push(' ');
 440                 }
 441                 // An additional space for the missing trailing separator.
 442                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 443                 {
 444                     result.push(' ');
 445                 }
 446             }
 447             if formatted_comment.contains('\n') {
 448                 item_max_width = None;
 449             }
 450             result.push_str(&formatted_comment);
 451         } else {
 452             item_max_width = None;
 453         }
 454
 455         if formatting.preserve_newline && !last && tactic == DefinitiveListTactic::Vertical &&
 456             item.new_lines
 457         {
 458             item_max_width = None;
 459             result.push('\n');
 460         }
 461     }
 462
 463     Some(result)
 464 }
 465
 466 fn max_width_of_item_with_post_comment<I, T>(
 467     items: &I,
 468     i: usize,
 469     overhead: usize,
 470     max_budget: usize,
 471 ) -> usize
 472 where
 473     I: IntoIterator<Item = T> + Clone,
 474     T: AsRef<ListItem>,
 475 {
 476     let mut max_width = 0;
 477     let mut first = true;
 478     for item in items.clone().into_iter().skip(i) {
 479         let item = item.as_ref();
 480         let inner_item_width = item.inner_as_ref().len();
 481         if !first &&
 482             (item.is_different_group() || !item.post_comment.is_some() ||
 483                 inner_item_width + overhead > max_budget)
 484         {
 485             return max_width;
 486         }
 487         if max_width < inner_item_width {
 488             max_width = inner_item_width;
 489         }
 490         if item.new_lines {
 491             return max_width;
 492         }
 493         first = false;
 494     }
 495     max_width
 496 }
 497
 498 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 499     item_max_width
 500         .and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
 501         .unwrap_or(0)
 502 }
 503
 504 pub struct ListItems<'a, I, F1, F2, F3>
 505 where
 506     I: Iterator,
 507 {
 508     codemap: &'a CodeMap,
 509     inner: Peekable<I>,
 510     get_lo: F1,
 511     get_hi: F2,
 512     get_item_string: F3,
 513     prev_span_end: BytePos,
 514     next_span_start: BytePos,
 515     terminator: &'a str,
 516     leave_last: bool,
 517 }
 518
 519 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 520 where
 521     I: Iterator<Item = T>,
 522     F1: Fn(&T) -> BytePos,
 523     F2: Fn(&T) -> BytePos,
 524     F3: Fn(&T) -> Option<String>,
 525 {
 526     type Item = ListItem;
 527
 528     fn next(&mut self) -> Option<Self::Item> {
 529         let white_space: &[_] = &[' ', '\t'];
 530
 531         self.inner.next().map(|item| {
 532             let mut new_lines = false;
 533             // Pre-comment
 534             let pre_snippet = self.codemap
 535                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 536                 .unwrap();
 537             let trimmed_pre_snippet = pre_snippet.trim();
 538             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 539             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 540             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 541                 (
 542                     Some(trimmed_pre_snippet.to_owned()),
 543                     ListItemCommentStyle::DifferentLine,
 544                 )
 545             } else if has_block_comment {
 546                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 547                 if pre_snippet
 548                     .chars()
 549                     .rev()
 550                     .take(comment_end + 1)
 551                     .any(|c| c == '\n')
 552                 {
 553                     (
 554                         Some(trimmed_pre_snippet.to_owned()),
 555                         ListItemCommentStyle::DifferentLine,
 556                     )
 557                 } else {
 558                     (
 559                         Some(trimmed_pre_snippet.to_owned()),
 560                         ListItemCommentStyle::SameLine,
 561                     )
 562                 }
 563             } else {
 564                 (None, ListItemCommentStyle::None)
 565             };
 566
 567             // Post-comment
 568             let next_start = match self.inner.peek() {
 569                 Some(next_item) => (self.get_lo)(next_item),
 570                 None => self.next_span_start,
 571             };
 572             let post_snippet = self.codemap
 573                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 574                 .unwrap();
 575
 576             let comment_end = match self.inner.peek() {
 577                 Some(..) => {
 578                     let mut block_open_index = post_snippet.find("/*");
 579                     // check if it realy is a block comment (and not //*)
 580                     if let Some(i) = block_open_index {
 581                         if i > 0 && &post_snippet[i - 1..i] == "/" {
 582                             block_open_index = None;
 583                         }
 584                     }
 585                     let newline_index = post_snippet.find('\n');
 586                     if let Some(separator_index) = post_snippet.find_uncommented(",") {
 587                         match (block_open_index, newline_index) {
 588                             // Separator before comment, with the next item on same line.
 589                             // Comment belongs to next item.
 590                             (Some(i), None) if i > separator_index => separator_index + 1,
 591                             // Block-style post-comment before the separator.
 592                             (Some(i), None) => cmp::max(
 593                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 594                                 separator_index + 1,
 595                             ),
 596                             // Block-style post-comment. Either before or after the separator.
 597                             (Some(i), Some(j)) if i < j => cmp::max(
 598                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 599                                 separator_index + 1,
 600                             ),
 601                             // Potential *single* line comment.
 602                             (_, Some(j)) if j > separator_index => j + 1,
 603                             _ => post_snippet.len(),
 604                         }
 605                     } else {
 606                         // Match arms may not have trailing comma. In any case, for match arms,
 607                         // we will assume that the post comment belongs to the next arm if they
 608                         // do not end with trailing comma.
 609                         1
 610                     }
 611                 }
 612                 None => post_snippet
 613                     .find_uncommented(self.terminator)
 614                     .unwrap_or_else(|| post_snippet.len()),
 615             };
 616
 617             if !post_snippet.is_empty() && comment_end > 0 {
 618                 // Account for extra whitespace between items. This is fiddly
 619                 // because of the way we divide pre- and post- comments.
 620
 621                 // Everything from the separator to the next item.
 622                 let test_snippet = &post_snippet[comment_end - 1..];
 623                 let first_newline = test_snippet
 624                     .find('\n')
 625                     .unwrap_or_else(|| test_snippet.len());
 626                 // From the end of the first line of comments.
 627                 let test_snippet = &test_snippet[first_newline..];
 628                 let first = test_snippet
 629                     .find(|c: char| !c.is_whitespace())
 630                     .unwrap_or_else(|| test_snippet.len());
 631                 // From the end of the first line of comments to the next non-whitespace char.
 632                 let test_snippet = &test_snippet[..first];
 633
 634                 if test_snippet.chars().filter(|c| c == &'\n').count() > 1 {
 635                     // There were multiple line breaks which got trimmed to nothing.
 636                     new_lines = true;
 637                 }
 638             }
 639
 640             // Cleanup post-comment: strip separators and whitespace.
 641             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 642             let post_snippet = post_snippet[..comment_end].trim();
 643
 644             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 645                 post_snippet[1..].trim_matches(white_space)
 646             } else if post_snippet.ends_with(',') {
 647                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 648             } else {
 649                 post_snippet
 650             };
 651
 652             let post_comment = if !post_snippet_trimmed.is_empty() {
 653                 Some(post_snippet_trimmed.to_owned())
 654             } else {
 655                 None
 656             };
 657
 658             ListItem {
 659                 pre_comment: pre_comment,
 660                 pre_comment_style: pre_comment_style,
 661                 item: if self.inner.peek().is_none() && self.leave_last {
 662                     None
 663                 } else {
 664                     (self.get_item_string)(&item)
 665                 },
 666                 post_comment: post_comment,
 667                 new_lines: new_lines,
 668             }
 669         })
 670     }
 671 }
 672
 673 // Creates an iterator over a list's items with associated comments.
 674 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 675     codemap: &'a CodeMap,
 676     inner: I,
 677     terminator: &'a str,
 678     get_lo: F1,
 679     get_hi: F2,
 680     get_item_string: F3,
 681     prev_span_end: BytePos,
 682     next_span_start: BytePos,
 683     leave_last: bool,
 684 ) -> ListItems<'a, I, F1, F2, F3>
 685 where
 686     I: Iterator<Item = T>,
 687     F1: Fn(&T) -> BytePos,
 688     F2: Fn(&T) -> BytePos,
 689     F3: Fn(&T) -> Option<String>,
 690 {
 691     ListItems {
 692         codemap: codemap,
 693         inner: inner.peekable(),
 694         get_lo: get_lo,
 695         get_hi: get_hi,
 696         get_item_string: get_item_string,
 697         prev_span_end: prev_span_end,
 698         next_span_start: next_span_start,
 699         terminator: terminator,
 700         leave_last: leave_last,
 701     }
 702 }
 703
 704 /// Returns the count and total width of the list items.
 705 fn calculate_width<I, T>(items: I) -> (usize, usize)
 706 where
 707     I: IntoIterator<Item = T>,
 708     T: AsRef<ListItem>,
 709 {
 710     items
 711         .into_iter()
 712         .map(|item| total_item_width(item.as_ref()))
 713         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 714 }
 715
 716 fn total_item_width(item: &ListItem) -> usize {
 717     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..])) +
 718         comment_len(item.post_comment.as_ref().map(|x| &(*x)[..])) +
 719         item.item.as_ref().map_or(0, |str| str.len())
 720 }
 721
 722 fn comment_len(comment: Option<&str>) -> usize {
 723     match comment {
 724         Some(s) => {
 725             let text_len = s.trim().len();
 726             if text_len > 0 {
 727                 // We'll put " /*" before and " */" after inline comments.
 728                 text_len + 6
 729             } else {
 730                 text_len
 731             }
 732         }
 733         None => 0,
 734     }
 735 }
 736
 737 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 738 pub fn struct_lit_shape(
 739     shape: Shape,
 740     context: &RewriteContext,
 741     prefix_width: usize,
 742     suffix_width: usize,
 743 ) -> Option<(Option<Shape>, Shape)> {
 744     let v_shape = match context.config.struct_lit_style() {
 745         IndentStyle::Visual => try_opt!(
 746             try_opt!(shape.visual_indent(0).shrink_left(prefix_width)).sub_width(suffix_width)
 747         ),
 748         IndentStyle::Block => {
 749             let shape = shape.block_indent(context.config.tab_spaces());
 750             Shape {
 751                 width: context.budget(shape.indent.width()),
 752                 ..shape
 753             }
 754         }
 755     };
 756     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 757     if let Some(w) = shape_width {
 758         let shape_width = cmp::min(w, context.config.struct_lit_width());
 759         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 760     } else {
 761         Some((None, v_shape))
 762     }
 763 }
 764
 765 // Compute the tactic for the internals of a struct-lit-like thing.
 766 pub fn struct_lit_tactic(
 767     h_shape: Option<Shape>,
 768     context: &RewriteContext,
 769     items: &[ListItem],
 770 ) -> DefinitiveListTactic {
 771     if let Some(h_shape) = h_shape {
 772         let prelim_tactic = match (context.config.struct_lit_style(), items.len()) {
 773             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 774             _ => context.config.struct_lit_multiline_style().to_list_tactic(),
 775         };
 776         definitive_tactic(items, prelim_tactic, Separator::Comma, h_shape.width)
 777     } else {
 778         DefinitiveListTactic::Vertical
 779     }
 780 }
 781
 782 // Given a tactic and possible shapes for horizontal and vertical layout,
 783 // come up with the actual shape to use.
 784 pub fn shape_for_tactic(
 785     tactic: DefinitiveListTactic,
 786     h_shape: Option<Shape>,
 787     v_shape: Shape,
 788 ) -> Shape {
 789     match tactic {
 790         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 791         _ => v_shape,
 792     }
 793 }
 794
 795 // Create a ListFormatting object for formatting the internals of a
 796 // struct-lit-like thing, that is a series of fields.
 797 pub fn struct_lit_formatting<'a>(
 798     shape: Shape,
 799     tactic: DefinitiveListTactic,
 800     context: &'a RewriteContext,
 801     force_no_trailing_comma: bool,
 802 ) -> ListFormatting<'a> {
 803     let ends_with_newline = context.config.struct_lit_style() != IndentStyle::Visual &&
 804         tactic == DefinitiveListTactic::Vertical;
 805     ListFormatting {
 806         tactic: tactic,
 807         separator: ",",
 808         trailing_separator: if force_no_trailing_comma {
 809             SeparatorTactic::Never
 810         } else {
 811             context.config.trailing_comma()
 812         },
 813         separator_place: SeparatorPlace::Back,
 814         shape: shape,
 815         ends_with_newline: ends_with_newline,
 816         preserve_newline: true,
 817         config: context.config,
 818     }
 819 }