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