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 //! Format list-like expressions and items.
  12
  13 use std::cmp;
  14 use std::iter::Peekable;
  15
  16 use config::lists::*;
  17 use syntax::codemap::BytePos;
  18
  19 use comment::{find_comment_end, rewrite_comment, FindUncommented};
  20 use config::{Config, IndentStyle};
  21 use rewrite::RewriteContext;
  22 use shape::{Indent, Shape};
  23 use utils::{count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline};
  24 use visitor::SnippetProvider;
  25
  26 pub struct ListFormatting<'a> {
  27     pub tactic: DefinitiveListTactic,
  28     pub separator: &'a str,
  29     pub trailing_separator: SeparatorTactic,
  30     pub separator_place: SeparatorPlace,
  31     pub shape: Shape,
  32     // Non-expressions, e.g. items, will have a new line at the end of the list.
  33     // Important for comment styles.
  34     pub ends_with_newline: bool,
  35     // Remove newlines between list elements for expressions.
  36     pub preserve_newline: bool,
  37     pub config: &'a Config,
  38 }
  39
  40 impl<'a> ListFormatting<'a> {
  41     pub fn needs_trailing_separator(&self) -> bool {
  42         match self.trailing_separator {
  43             // We always put separator in front.
  44             SeparatorTactic::Always => true,
  45             SeparatorTactic::Vertical => self.tactic == DefinitiveListTactic::Vertical,
  46             SeparatorTactic::Never => {
  47                 self.tactic == DefinitiveListTactic::Vertical && self.separator_place.is_front()
  48             }
  49         }
  50     }
  51 }
  52
  53 impl AsRef<ListItem> for ListItem {
  54     fn as_ref(&self) -> &ListItem {
  55         self
  56     }
  57 }
  58
  59 #[derive(PartialEq, Eq, Debug, Copy, Clone)]
  60 pub enum ListItemCommentStyle {
  61     // Try to keep the comment on the same line with the item.
  62     SameLine,
  63     // Put the comment on the previous or the next line of the item.
  64     DifferentLine,
  65     // No comment available.
  66     None,
  67 }
  68
  69 #[derive(Debug, Clone)]
  70 pub struct ListItem {
  71     // None for comments mean that they are not present.
  72     pub pre_comment: Option<String>,
  73     pub pre_comment_style: ListItemCommentStyle,
  74     // Item should include attributes and doc comments. None indicates a failed
  75     // rewrite.
  76     pub item: Option<String>,
  77     pub post_comment: Option<String>,
  78     // Whether there is extra whitespace before this item.
  79     pub new_lines: bool,
  80 }
  81
  82 impl ListItem {
  83     pub fn empty() -> ListItem {
  84         ListItem {
  85             pre_comment: None,
  86             pre_comment_style: ListItemCommentStyle::None,
  87             item: None,
  88             post_comment: None,
  89             new_lines: false,
  90         }
  91     }
  92
  93     pub fn inner_as_ref(&self) -> &str {
  94         self.item.as_ref().map_or("", |s| s)
  95     }
  96
  97     pub fn is_different_group(&self) -> bool {
  98         self.inner_as_ref().contains('\n') || self.pre_comment.is_some()
  99             || self.post_comment
 100                 .as_ref()
 101                 .map_or(false, |s| s.contains('\n'))
 102     }
 103
 104     pub fn is_multiline(&self) -> bool {
 105         self.inner_as_ref().contains('\n')
 106             || self.pre_comment
 107                 .as_ref()
 108                 .map_or(false, |s| s.contains('\n'))
 109             || self.post_comment
 110                 .as_ref()
 111                 .map_or(false, |s| s.contains('\n'))
 112     }
 113
 114     pub fn has_single_line_comment(&self) -> bool {
 115         self.pre_comment
 116             .as_ref()
 117             .map_or(false, |comment| comment.trim_left().starts_with("//"))
 118             || self.post_comment
 119                 .as_ref()
 120                 .map_or(false, |comment| comment.trim_left().starts_with("//"))
 121     }
 122
 123     pub fn has_comment(&self) -> bool {
 124         self.pre_comment.is_some() || self.post_comment.is_some()
 125     }
 126
 127     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 128         ListItem {
 129             pre_comment: None,
 130             pre_comment_style: ListItemCommentStyle::None,
 131             item: Some(s.into()),
 132             post_comment: None,
 133             new_lines: false,
 134         }
 135     }
 136
 137     // true if the item causes something to be written.
 138     fn is_substantial(&self) -> bool {
 139         fn empty(s: &Option<String>) -> bool {
 140             match *s {
 141                 Some(ref s) if !s.is_empty() => false,
 142                 _ => true,
 143             }
 144         }
 145
 146         !(empty(&self.pre_comment) && empty(&self.item) && empty(&self.post_comment))
 147     }
 148 }
 149
 150 /// The type of separator for lists.
 151 #[derive(Copy, Clone, Eq, PartialEq, Debug)]
 152 pub enum Separator {
 153     Comma,
 154     VerticalBar,
 155 }
 156
 157 impl Separator {
 158     pub fn len(&self) -> usize {
 159         match *self {
 160             // 2 = `, `
 161             Separator::Comma => 2,
 162             // 3 = ` | `
 163             Separator::VerticalBar => 3,
 164         }
 165     }
 166 }
 167
 168 pub fn definitive_tactic<I, T>(
 169     items: I,
 170     tactic: ListTactic,
 171     sep: Separator,
 172     width: usize,
 173 ) -> DefinitiveListTactic
 174 where
 175     I: IntoIterator<Item = T> + Clone,
 176     T: AsRef<ListItem>,
 177 {
 178     let pre_line_comments = items
 179         .clone()
 180         .into_iter()
 181         .any(|item| item.as_ref().has_single_line_comment());
 182
 183     let limit = match tactic {
 184         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 185         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 186         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 187         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 188         ListTactic::Mixed | ListTactic::HorizontalVertical => width,
 189     };
 190
 191     let (sep_count, total_width) = calculate_width(items.clone());
 192     let total_sep_len = sep.len() * sep_count.checked_sub(1).unwrap_or(0);
 193     let real_total = total_width + total_sep_len;
 194
 195     if real_total <= limit
 196         && !pre_line_comments
 197         && !items.into_iter().any(|item| item.as_ref().is_multiline())
 198     {
 199         DefinitiveListTactic::Horizontal
 200     } else {
 201         match tactic {
 202             ListTactic::Mixed => DefinitiveListTactic::Mixed,
 203             _ => DefinitiveListTactic::Vertical,
 204         }
 205     }
 206 }
 207
 208 // Format a list of commented items into a string.
 209 // TODO: add unit tests
 210 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 211 where
 212     I: IntoIterator<Item = T> + Clone,
 213     T: AsRef<ListItem>,
 214 {
 215     let tactic = formatting.tactic;
 216     let sep_len = formatting.separator.len();
 217
 218     // Now that we know how we will layout, we can decide for sure if there
 219     // will be a trailing separator.
 220     let mut trailing_separator = formatting.needs_trailing_separator();
 221     let mut result = String::with_capacity(128);
 222     let cloned_items = items.clone();
 223     let mut iter = items.into_iter().enumerate().peekable();
 224     let mut item_max_width: Option<usize> = None;
 225     let sep_place =
 226         SeparatorPlace::from_tactic(formatting.separator_place, tactic, formatting.separator);
 227
 228     let mut line_len = 0;
 229     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 230     while let Some((i, item)) = iter.next() {
 231         let item = item.as_ref();
 232         let inner_item = item.item.as_ref()?;
 233         let first = i == 0;
 234         let last = iter.peek().is_none();
 235         let mut separate = match sep_place {
 236             SeparatorPlace::Front => !first,
 237             SeparatorPlace::Back => !last || trailing_separator,
 238         };
 239         let item_sep_len = if separate { sep_len } else { 0 };
 240
 241         // Item string may be multi-line. Its length (used for block comment alignment)
 242         // should be only the length of the last line.
 243         let item_last_line = if item.is_multiline() {
 244             inner_item.lines().last().unwrap_or("")
 245         } else {
 246             inner_item.as_ref()
 247         };
 248         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 249         if item_last_line.starts_with(&**indent_str) {
 250             item_last_line_width -= indent_str.len();
 251         }
 252
 253         if !item.is_substantial() {
 254             continue;
 255         }
 256
 257         match tactic {
 258             DefinitiveListTactic::Horizontal if !first => {
 259                 result.push(' ');
 260             }
 261             DefinitiveListTactic::SpecialMacro(num_args_before) => {
 262                 if i == 0 {
 263                     // Nothing
 264                 } else if i < num_args_before {
 265                     result.push(' ');
 266                 } else if i <= num_args_before + 1 {
 267                     result.push('\n');
 268                     result.push_str(indent_str);
 269                 } else {
 270                     result.push(' ');
 271                 }
 272             }
 273             DefinitiveListTactic::Vertical
 274                 if !first && !inner_item.is_empty() && !result.is_empty() =>
 275             {
 276                 result.push('\n');
 277                 result.push_str(indent_str);
 278             }
 279             DefinitiveListTactic::Mixed => {
 280                 let total_width = total_item_width(item) + item_sep_len;
 281
 282                 // 1 is space between separator and item.
 283                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 284                     result.push('\n');
 285                     result.push_str(indent_str);
 286                     line_len = 0;
 287                     if formatting.ends_with_newline {
 288                         trailing_separator = true;
 289                     }
 290                 }
 291
 292                 if last && formatting.ends_with_newline {
 293                     separate = formatting.trailing_separator != SeparatorTactic::Never;
 294                 }
 295
 296                 if line_len > 0 {
 297                     result.push(' ');
 298                     line_len += 1;
 299                 }
 300
 301                 line_len += total_width;
 302             }
 303             _ => {}
 304         }
 305
 306         // Pre-comments
 307         if let Some(ref comment) = item.pre_comment {
 308             // Block style in non-vertical mode.
 309             let block_mode = tactic != DefinitiveListTactic::Vertical;
 310             // Width restriction is only relevant in vertical mode.
 311             let comment =
 312                 rewrite_comment(comment, block_mode, formatting.shape, formatting.config)?;
 313             result.push_str(&comment);
 314
 315             if !inner_item.is_empty() {
 316                 if tactic == DefinitiveListTactic::Vertical {
 317                     // We cannot keep pre-comments on the same line if the comment if normalized.
 318                     let keep_comment = if formatting.config.normalize_comments()
 319                         || item.pre_comment_style == ListItemCommentStyle::DifferentLine
 320                     {
 321                         false
 322                     } else {
 323                         // We will try to keep the comment on the same line with the item here.
 324                         // 1 = ` `
 325                         let total_width = total_item_width(item) + item_sep_len + 1;
 326                         total_width <= formatting.shape.width
 327                     };
 328                     if keep_comment {
 329                         result.push(' ');
 330                     } else {
 331                         result.push('\n');
 332                         result.push_str(indent_str);
 333                     }
 334                 } else {
 335                     result.push(' ');
 336                 }
 337             }
 338             item_max_width = None;
 339         }
 340
 341         if separate && sep_place.is_front() && !first {
 342             result.push_str(formatting.separator.trim());
 343             result.push(' ');
 344         }
 345         result.push_str(inner_item);
 346
 347         // Post-comments
 348         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 349             let comment = item.post_comment.as_ref().unwrap();
 350             let formatted_comment = rewrite_comment(
 351                 comment,
 352                 true,
 353                 Shape::legacy(formatting.shape.width, Indent::empty()),
 354                 formatting.config,
 355             )?;
 356
 357             result.push(' ');
 358             result.push_str(&formatted_comment);
 359         }
 360
 361         if separate && sep_place.is_back() {
 362             result.push_str(formatting.separator);
 363         }
 364
 365         if tactic == DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 366             let comment = item.post_comment.as_ref().unwrap();
 367             let overhead = last_line_width(&result) + first_line_width(comment.trim());
 368
 369             let rewrite_post_comment = |item_max_width: &mut Option<usize>| {
 370                 if item_max_width.is_none() && !last && !inner_item.contains('\n') {
 371                     *item_max_width = Some(max_width_of_item_with_post_comment(
 372                         &cloned_items,
 373                         i,
 374                         overhead,
 375                         formatting.config.max_width(),
 376                     ));
 377                 }
 378                 let overhead = if starts_with_newline(comment) {
 379                     0
 380                 } else if let Some(max_width) = *item_max_width {
 381                     max_width + 2
 382                 } else {
 383                     // 1 = space between item and comment.
 384                     item_last_line_width + 1
 385                 };
 386                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
 387                 let offset = formatting.shape.indent + overhead;
 388                 let comment_shape = Shape::legacy(width, offset);
 389
 390                 // Use block-style only for the last item or multiline comments.
 391                 let block_style = !formatting.ends_with_newline && last
 392                     || comment.trim().contains('\n')
 393                     || comment.trim().len() > width;
 394
 395                 rewrite_comment(
 396                     comment.trim_left(),
 397                     block_style,
 398                     comment_shape,
 399                     formatting.config,
 400                 )
 401             };
 402
 403             let mut formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 404
 405             if !starts_with_newline(comment) {
 406                 let mut comment_alignment =
 407                     post_comment_alignment(item_max_width, inner_item.len());
 408                 if first_line_width(&formatted_comment)
 409                     + last_line_width(&result)
 410                     + comment_alignment
 411                     + 1 > formatting.config.max_width()
 412                 {
 413                     item_max_width = None;
 414                     formatted_comment = rewrite_post_comment(&mut item_max_width)?;
 415                     comment_alignment = post_comment_alignment(item_max_width, inner_item.len());
 416                 }
 417                 for _ in 0..(comment_alignment + 1) {
 418                     result.push(' ');
 419                 }
 420                 // An additional space for the missing trailing separator.
 421                 if last && item_max_width.is_some() && !separate && !formatting.separator.is_empty()
 422                 {
 423                     result.push(' ');
 424                 }
 425             } else {
 426                 result.push('\n');
 427                 result.push_str(indent_str);
 428             }
 429             if formatted_comment.contains('\n') {
 430                 item_max_width = None;
 431             }
 432             result.push_str(&formatted_comment);
 433         } else {
 434             item_max_width = None;
 435         }
 436
 437         if formatting.preserve_newline
 438             && !last
 439             && tactic == DefinitiveListTactic::Vertical
 440             && item.new_lines
 441         {
 442             item_max_width = None;
 443             result.push('\n');
 444         }
 445     }
 446
 447     Some(result)
 448 }
 449
 450 fn max_width_of_item_with_post_comment<I, T>(
 451     items: &I,
 452     i: usize,
 453     overhead: usize,
 454     max_budget: usize,
 455 ) -> usize
 456 where
 457     I: IntoIterator<Item = T> + Clone,
 458     T: AsRef<ListItem>,
 459 {
 460     let mut max_width = 0;
 461     let mut first = true;
 462     for item in items.clone().into_iter().skip(i) {
 463         let item = item.as_ref();
 464         let inner_item_width = item.inner_as_ref().len();
 465         if !first
 466             && (item.is_different_group()
 467                 || item.post_comment.is_none()
 468                 || inner_item_width + overhead > max_budget)
 469         {
 470             return max_width;
 471         }
 472         if max_width < inner_item_width {
 473             max_width = inner_item_width;
 474         }
 475         if item.new_lines {
 476             return max_width;
 477         }
 478         first = false;
 479     }
 480     max_width
 481 }
 482
 483 fn post_comment_alignment(item_max_width: Option<usize>, inner_item_len: usize) -> usize {
 484     item_max_width
 485         .and_then(|max_line_width| max_line_width.checked_sub(inner_item_len))
 486         .unwrap_or(0)
 487 }
 488
 489 pub struct ListItems<'a, I, F1, F2, F3>
 490 where
 491     I: Iterator,
 492 {
 493     snippet_provider: &'a SnippetProvider<'a>,
 494     inner: Peekable<I>,
 495     get_lo: F1,
 496     get_hi: F2,
 497     get_item_string: F3,
 498     prev_span_end: BytePos,
 499     next_span_start: BytePos,
 500     terminator: &'a str,
 501     separator: &'a str,
 502     leave_last: bool,
 503 }
 504
 505 impl<'a, T, I, F1, F2, F3> Iterator for ListItems<'a, I, F1, F2, F3>
 506 where
 507     I: Iterator<Item = T>,
 508     F1: Fn(&T) -> BytePos,
 509     F2: Fn(&T) -> BytePos,
 510     F3: Fn(&T) -> Option<String>,
 511 {
 512     type Item = ListItem;
 513
 514     fn next(&mut self) -> Option<Self::Item> {
 515         let white_space: &[_] = &[' ', '\t'];
 516
 517         self.inner.next().map(|item| {
 518             let mut new_lines = false;
 519             // Pre-comment
 520             let pre_snippet = self.snippet_provider
 521                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 522                 .unwrap();
 523             let trimmed_pre_snippet = pre_snippet.trim();
 524             let has_single_line_comment = trimmed_pre_snippet.starts_with("//");
 525             let has_block_comment = trimmed_pre_snippet.starts_with("/*");
 526             let (pre_comment, pre_comment_style) = if has_single_line_comment {
 527                 (
 528                     Some(trimmed_pre_snippet.to_owned()),
 529                     ListItemCommentStyle::DifferentLine,
 530                 )
 531             } else if has_block_comment {
 532                 let comment_end = pre_snippet.chars().rev().position(|c| c == '/').unwrap();
 533                 if pre_snippet
 534                     .chars()
 535                     .rev()
 536                     .take(comment_end + 1)
 537                     .any(|c| c == '\n')
 538                 {
 539                     (
 540                         Some(trimmed_pre_snippet.to_owned()),
 541                         ListItemCommentStyle::DifferentLine,
 542                     )
 543                 } else {
 544                     (
 545                         Some(trimmed_pre_snippet.to_owned()),
 546                         ListItemCommentStyle::SameLine,
 547                     )
 548                 }
 549             } else {
 550                 (None, ListItemCommentStyle::None)
 551             };
 552
 553             // Post-comment
 554             let next_start = match self.inner.peek() {
 555                 Some(next_item) => (self.get_lo)(next_item),
 556                 None => self.next_span_start,
 557             };
 558             let post_snippet = self.snippet_provider
 559                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
 560                 .unwrap();
 561
 562             let comment_end = match self.inner.peek() {
 563                 Some(..) => {
 564                     let mut block_open_index = post_snippet.find("/*");
 565                     // check if it really is a block comment (and not `//*` or a nested comment)
 566                     if let Some(i) = block_open_index {
 567                         match post_snippet.find('/') {
 568                             Some(j) if j < i => block_open_index = None,
 569                             _ if i > 0 && &post_snippet[i - 1..i] == "/" => block_open_index = None,
 570                             _ => (),
 571                         }
 572                     }
 573                     let newline_index = post_snippet.find('\n');
 574                     if let Some(separator_index) = post_snippet.find_uncommented(self.separator) {
 575                         match (block_open_index, newline_index) {
 576                             // Separator before comment, with the next item on same line.
 577                             // Comment belongs to next item.
 578                             (Some(i), None) if i > separator_index => separator_index + 1,
 579                             // Block-style post-comment before the separator.
 580                             (Some(i), None) => cmp::max(
 581                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 582                                 separator_index + 1,
 583                             ),
 584                             // Block-style post-comment. Either before or after the separator.
 585                             (Some(i), Some(j)) if i < j => cmp::max(
 586                                 find_comment_end(&post_snippet[i..]).unwrap() + i,
 587                                 separator_index + 1,
 588                             ),
 589                             // Potential *single* line comment.
 590                             (_, Some(j)) if j > separator_index => j + 1,
 591                             _ => post_snippet.len(),
 592                         }
 593                     } else if let Some(newline_index) = newline_index {
 594                         // Match arms may not have trailing comma. In any case, for match arms,
 595                         // we will assume that the post comment belongs to the next arm if they
 596                         // do not end with trailing comma.
 597                         newline_index + 1
 598                     } else {
 599                         0
 600                     }
 601                 }
 602                 None => post_snippet
 603                     .find_uncommented(self.terminator)
 604                     .unwrap_or_else(|| post_snippet.len()),
 605             };
 606
 607             if !post_snippet.is_empty() && comment_end > 0 {
 608                 // Account for extra whitespace between items. This is fiddly
 609                 // because of the way we divide pre- and post- comments.
 610
 611                 // Everything from the separator to the next item.
 612                 let test_snippet = &post_snippet[comment_end - 1..];
 613                 let first_newline = test_snippet
 614                     .find('\n')
 615                     .unwrap_or_else(|| test_snippet.len());
 616                 // From the end of the first line of comments.
 617                 let test_snippet = &test_snippet[first_newline..];
 618                 let first = test_snippet
 619                     .find(|c: char| !c.is_whitespace())
 620                     .unwrap_or_else(|| test_snippet.len());
 621                 // From the end of the first line of comments to the next non-whitespace char.
 622                 let test_snippet = &test_snippet[..first];
 623
 624                 if count_newlines(test_snippet) > 1 {
 625                     // There were multiple line breaks which got trimmed to nothing.
 626                     new_lines = true;
 627                 }
 628             }
 629
 630             // Cleanup post-comment: strip separators and whitespace.
 631             self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 632             let post_snippet = post_snippet[..comment_end].trim();
 633
 634             let post_snippet_trimmed = if post_snippet.starts_with(|c| c == ',' || c == ':') {
 635                 post_snippet[1..].trim_matches(white_space)
 636             } else if post_snippet.starts_with(self.separator) {
 637                 post_snippet[self.separator.len()..].trim_matches(white_space)
 638             } else if post_snippet.ends_with(',') {
 639                 post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 640             } else {
 641                 post_snippet
 642             };
 643
 644             let post_comment = if !post_snippet_trimmed.is_empty() {
 645                 Some(post_snippet_trimmed.to_owned())
 646             } else {
 647                 None
 648             };
 649
 650             ListItem {
 651                 pre_comment,
 652                 pre_comment_style,
 653                 item: if self.inner.peek().is_none() && self.leave_last {
 654                     None
 655                 } else {
 656                     (self.get_item_string)(&item)
 657                 },
 658                 post_comment,
 659                 new_lines,
 660             }
 661         })
 662     }
 663 }
 664
 665 #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
 666 // Creates an iterator over a list's items with associated comments.
 667 pub fn itemize_list<'a, T, I, F1, F2, F3>(
 668     snippet_provider: &'a SnippetProvider,
 669     inner: I,
 670     terminator: &'a str,
 671     separator: &'a str,
 672     get_lo: F1,
 673     get_hi: F2,
 674     get_item_string: F3,
 675     prev_span_end: BytePos,
 676     next_span_start: BytePos,
 677     leave_last: bool,
 678 ) -> ListItems<'a, I, F1, F2, F3>
 679 where
 680     I: Iterator<Item = T>,
 681     F1: Fn(&T) -> BytePos,
 682     F2: Fn(&T) -> BytePos,
 683     F3: Fn(&T) -> Option<String>,
 684 {
 685     ListItems {
 686         snippet_provider,
 687         inner: inner.peekable(),
 688         get_lo,
 689         get_hi,
 690         get_item_string,
 691         prev_span_end,
 692         next_span_start,
 693         terminator,
 694         separator,
 695         leave_last,
 696     }
 697 }
 698
 699 /// Returns the count and total width of the list items.
 700 fn calculate_width<I, T>(items: I) -> (usize, usize)
 701 where
 702     I: IntoIterator<Item = T>,
 703     T: AsRef<ListItem>,
 704 {
 705     items
 706         .into_iter()
 707         .map(|item| total_item_width(item.as_ref()))
 708         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 709 }
 710
 711 pub fn total_item_width(item: &ListItem) -> usize {
 712     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..]))
 713         + comment_len(item.post_comment.as_ref().map(|x| &(*x)[..]))
 714         + item.item.as_ref().map_or(0, |str| str.len())
 715 }
 716
 717 fn comment_len(comment: Option<&str>) -> usize {
 718     match comment {
 719         Some(s) => {
 720             let text_len = s.trim().len();
 721             if text_len > 0 {
 722                 // We'll put " /*" before and " */" after inline comments.
 723                 text_len + 6
 724             } else {
 725                 text_len
 726             }
 727         }
 728         None => 0,
 729     }
 730 }
 731
 732 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 733 pub fn struct_lit_shape(
 734     shape: Shape,
 735     context: &RewriteContext,
 736     prefix_width: usize,
 737     suffix_width: usize,
 738 ) -> Option<(Option<Shape>, Shape)> {
 739     let v_shape = match context.config.indent_style() {
 740         IndentStyle::Visual => shape
 741             .visual_indent(0)
 742             .shrink_left(prefix_width)?
 743             .sub_width(suffix_width)?,
 744         IndentStyle::Block => {
 745             let shape = shape.block_indent(context.config.tab_spaces());
 746             Shape {
 747                 width: context.budget(shape.indent.width()),
 748                 ..shape
 749             }
 750         }
 751     };
 752     let shape_width = shape.width.checked_sub(prefix_width + suffix_width);
 753     if let Some(w) = shape_width {
 754         let shape_width = cmp::min(w, context.config.width_heuristics().struct_lit_width);
 755         Some((Some(Shape::legacy(shape_width, shape.indent)), v_shape))
 756     } else {
 757         Some((None, v_shape))
 758     }
 759 }
 760
 761 // Compute the tactic for the internals of a struct-lit-like thing.
 762 pub fn struct_lit_tactic(
 763     h_shape: Option<Shape>,
 764     context: &RewriteContext,
 765     items: &[ListItem],
 766 ) -> DefinitiveListTactic {
 767     if let Some(h_shape) = h_shape {
 768         let prelim_tactic = match (context.config.indent_style(), items.len()) {
 769             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 770             _ if context.config.struct_lit_single_line() => ListTactic::HorizontalVertical,
 771             _ => ListTactic::Vertical,
 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.indent_style() != IndentStyle::Visual
 801         && tactic == DefinitiveListTactic::Vertical;
 802     ListFormatting {
 803         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,
 812         ends_with_newline,
 813         preserve_newline: true,
 814         config: context.config,
 815     }
 816 }