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