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