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