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::{self, 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
  21 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  22 /// Formatting tactic for lists. This will be cast down to a
  23 /// DefinitiveListTactic depending on the number and length of the items and
  24 /// their comments.
  25 pub enum ListTactic {
  26     // One item per row.
  27     Vertical,
  28     // All items on one row.
  29     Horizontal,
  30     // Try Horizontal layout, if that fails then vertical.
  31     HorizontalVertical,
  32     // HorizontalVertical with a soft limit of n characters.
  33     LimitedHorizontalVertical(usize),
  34     // Pack as many items as possible per row over (possibly) many rows.
  35     Mixed,
  36 }
  37
  38 impl_enum_decodable!(ListTactic, Vertical, Horizontal, HorizontalVertical, Mixed);
  39
  40 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  41 pub enum SeparatorTactic {
  42     Always,
  43     Never,
  44     Vertical,
  45 }
  46
  47 impl_enum_decodable!(SeparatorTactic, Always, Never, Vertical);
  48
  49 impl SeparatorTactic {
  50     pub fn from_bool(b: bool) -> SeparatorTactic {
  51         if b {
  52             SeparatorTactic::Always
  53         } else {
  54             SeparatorTactic::Never
  55         }
  56     }
  57 }
  58
  59 pub struct ListFormatting<'a> {
  60     pub tactic: DefinitiveListTactic,
  61     pub separator: &'a str,
  62     pub trailing_separator: SeparatorTactic,
  63     pub shape: Shape,
  64     // Non-expressions, e.g. items, will have a new line at the end of the list.
  65     // Important for comment styles.
  66     pub ends_with_newline: bool,
  67     pub config: &'a Config,
  68 }
  69
  70 pub fn format_fn_args<I>(items: I, shape: Shape, config: &Config) -> Option<String>
  71     where I: Iterator<Item = ListItem>
  72 {
  73     list_helper(items,
  74                 shape,
  75                 config,
  76                 ListTactic::LimitedHorizontalVertical(config.fn_call_width))
  77 }
  78
  79 pub fn format_item_list<I>(items: I, shape: Shape, config: &Config) -> Option<String>
  80     where I: Iterator<Item = ListItem>
  81 {
  82     list_helper(items, shape, config, ListTactic::HorizontalVertical)
  83 }
  84
  85 pub fn list_helper<I>(items: I, shape: Shape, config: &Config, tactic: ListTactic) -> Option<String>
  86     where I: Iterator<Item = ListItem>
  87 {
  88     let item_vec: Vec<_> = items.collect();
  89     let tactic = definitive_tactic(&item_vec, tactic, shape.width);
  90     let fmt = ListFormatting {
  91         tactic: tactic,
  92         separator: ",",
  93         trailing_separator: SeparatorTactic::Never,
  94         shape: shape,
  95         ends_with_newline: false,
  96         config: config,
  97     };
  98
  99     write_list(&item_vec, &fmt)
 100 }
 101
 102 impl AsRef<ListItem> for ListItem {
 103     fn as_ref(&self) -> &ListItem {
 104         self
 105     }
 106 }
 107
 108 pub struct ListItem {
 109     // None for comments mean that they are not present.
 110     pub pre_comment: Option<String>,
 111     // Item should include attributes and doc comments. None indicates a failed
 112     // rewrite.
 113     pub item: Option<String>,
 114     pub post_comment: Option<String>,
 115     // Whether there is extra whitespace before this item.
 116     pub new_lines: bool,
 117 }
 118
 119 impl ListItem {
 120     pub fn is_multiline(&self) -> bool {
 121         self.item.as_ref().map_or(false, |s| s.contains('\n')) || self.pre_comment.is_some() ||
 122         self.post_comment
 123             .as_ref()
 124             .map_or(false, |s| s.contains('\n'))
 125     }
 126
 127     pub fn has_line_pre_comment(&self) -> bool {
 128         self.pre_comment
 129             .as_ref()
 130             .map_or(false, |comment| comment.starts_with("//"))
 131     }
 132
 133     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
 134         ListItem {
 135             pre_comment: None,
 136             item: Some(s.into()),
 137             post_comment: None,
 138             new_lines: false,
 139         }
 140     }
 141 }
 142
 143 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
 144 /// The definitive formatting tactic for lists.
 145 pub enum DefinitiveListTactic {
 146     Vertical,
 147     Horizontal,
 148     Mixed,
 149 }
 150
 151 pub fn definitive_tactic<I, T>(items: I, tactic: ListTactic, width: usize) -> DefinitiveListTactic
 152     where I: IntoIterator<Item = T> + Clone,
 153           T: AsRef<ListItem>
 154 {
 155     let pre_line_comments = items
 156         .clone()
 157         .into_iter()
 158         .any(|item| item.as_ref().has_line_pre_comment());
 159
 160     let limit = match tactic {
 161         _ if pre_line_comments => return DefinitiveListTactic::Vertical,
 162         ListTactic::Mixed => return DefinitiveListTactic::Mixed,
 163         ListTactic::Horizontal => return DefinitiveListTactic::Horizontal,
 164         ListTactic::Vertical => return DefinitiveListTactic::Vertical,
 165         ListTactic::LimitedHorizontalVertical(limit) => ::std::cmp::min(width, limit),
 166         ListTactic::HorizontalVertical => width,
 167     };
 168
 169     let (sep_count, total_width) = calculate_width(items.clone());
 170     let sep_len = ", ".len(); // FIXME: make more generic?
 171     let total_sep_len = sep_len * sep_count.checked_sub(1).unwrap_or(0);
 172     let real_total = total_width + total_sep_len;
 173
 174     if real_total <= limit && !pre_line_comments &&
 175        !items
 176             .into_iter()
 177             .any(|item| item.as_ref().is_multiline()) {
 178         DefinitiveListTactic::Horizontal
 179     } else {
 180         DefinitiveListTactic::Vertical
 181     }
 182 }
 183
 184 // Format a list of commented items into a string.
 185 // TODO: add unit tests
 186 pub fn write_list<I, T>(items: I, formatting: &ListFormatting) -> Option<String>
 187     where I: IntoIterator<Item = T>,
 188           T: AsRef<ListItem>
 189 {
 190     let tactic = formatting.tactic;
 191     let sep_len = formatting.separator.len();
 192
 193     // Now that we know how we will layout, we can decide for sure if there
 194     // will be a trailing separator.
 195     let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
 196     let mut result = String::new();
 197     let mut iter = items.into_iter().enumerate().peekable();
 198
 199     let mut line_len = 0;
 200     let indent_str = &formatting.shape.indent.to_string(formatting.config);
 201     while let Some((i, item)) = iter.next() {
 202         let item = item.as_ref();
 203         let inner_item = try_opt!(item.item.as_ref());
 204         let first = i == 0;
 205         let last = iter.peek().is_none();
 206         let separate = !last || trailing_separator;
 207         let item_sep_len = if separate { sep_len } else { 0 };
 208
 209         // Item string may be multi-line. Its length (used for block comment alignment)
 210         // should be only the length of the last line.
 211         let item_last_line = if item.is_multiline() {
 212             inner_item.lines().last().unwrap_or("")
 213         } else {
 214             inner_item.as_ref()
 215         };
 216         let mut item_last_line_width = item_last_line.len() + item_sep_len;
 217         if item_last_line.starts_with(indent_str) {
 218             item_last_line_width -= indent_str.len();
 219         }
 220
 221         match tactic {
 222             DefinitiveListTactic::Horizontal if !first => {
 223                 result.push(' ');
 224             }
 225             DefinitiveListTactic::Vertical if !first => {
 226                 result.push('\n');
 227                 result.push_str(indent_str);
 228             }
 229             DefinitiveListTactic::Mixed => {
 230                 let total_width = total_item_width(item) + item_sep_len;
 231
 232                 // 1 is space between separator and item.
 233                 if line_len > 0 && line_len + 1 + total_width > formatting.shape.width {
 234                     result.push('\n');
 235                     result.push_str(indent_str);
 236                     line_len = 0;
 237                 }
 238
 239                 if line_len > 0 {
 240                     result.push(' ');
 241                     line_len += 1;
 242                 }
 243
 244                 line_len += total_width;
 245             }
 246             _ => {}
 247         }
 248
 249         // Pre-comments
 250         if let Some(ref comment) = item.pre_comment {
 251             // Block style in non-vertical mode.
 252             let block_mode = tactic != DefinitiveListTactic::Vertical;
 253             // Width restriction is only relevant in vertical mode.
 254             let comment =
 255                 try_opt!(rewrite_comment(comment, block_mode, formatting.shape, formatting.config));
 256             result.push_str(&comment);
 257
 258             if tactic == DefinitiveListTactic::Vertical {
 259                 result.push('\n');
 260                 result.push_str(indent_str);
 261             } else {
 262                 result.push(' ');
 263             }
 264         }
 265
 266         result.push_str(&inner_item[..]);
 267
 268         // Post-comments
 269         if tactic != DefinitiveListTactic::Vertical && item.post_comment.is_some() {
 270             let comment = item.post_comment.as_ref().unwrap();
 271             let formatted_comment = 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
 345             .next()
 346             .map(|item| {
 347                 let mut new_lines = false;
 348                 // Pre-comment
 349                 let pre_snippet = self.codemap
 350                     .span_to_snippet(codemap::mk_sp(self.prev_span_end, (self.get_lo)(&item)))
 351                     .unwrap();
 352                 let trimmed_pre_snippet = pre_snippet.trim();
 353                 let has_pre_comment = trimmed_pre_snippet.contains("//") ||
 354                                       trimmed_pre_snippet.contains("/*");
 355                 let pre_comment = if has_pre_comment {
 356                     Some(trimmed_pre_snippet.to_owned())
 357                 } else {
 358                     None
 359                 };
 360
 361                 // Post-comment
 362                 let next_start = match self.inner.peek() {
 363                     Some(next_item) => (self.get_lo)(next_item),
 364                     None => self.next_span_start,
 365                 };
 366                 let post_snippet = self.codemap
 367                     .span_to_snippet(codemap::mk_sp((self.get_hi)(&item), next_start))
 368                     .unwrap();
 369
 370                 let comment_end = match self.inner.peek() {
 371                     Some(..) => {
 372                         let mut block_open_index = post_snippet.find("/*");
 373                         // check if it realy is a block comment (and not //*)
 374                         if let Some(i) = block_open_index {
 375                             if i > 0 && &post_snippet[i - 1..i] == "/" {
 376                                 block_open_index = None;
 377                             }
 378                         }
 379                         let newline_index = post_snippet.find('\n');
 380                         let separator_index = post_snippet.find_uncommented(",").unwrap();
 381
 382                         match (block_open_index, newline_index) {
 383                             // Separator before comment, with the next item on same line.
 384                             // Comment belongs to next item.
 385                             (Some(i), None) if i > separator_index => separator_index + 1,
 386                             // Block-style post-comment before the separator.
 387                             (Some(i), None) => {
 388                                 cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 389                                          separator_index + 1)
 390                             }
 391                             // Block-style post-comment. Either before or after the separator.
 392                             (Some(i), Some(j)) if i < j => {
 393                                 cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 394                                          separator_index + 1)
 395                             }
 396                             // Potential *single* line comment.
 397                             (_, Some(j)) if j > separator_index => j + 1,
 398                             _ => post_snippet.len(),
 399                         }
 400                     }
 401                     None => {
 402                         post_snippet
 403                             .find_uncommented(self.terminator)
 404                             .unwrap_or(post_snippet.len())
 405                     }
 406                 };
 407
 408                 if !post_snippet.is_empty() && comment_end > 0 {
 409                     // Account for extra whitespace between items. This is fiddly
 410                     // because of the way we divide pre- and post- comments.
 411
 412                     // Everything from the separator to the next item.
 413                     let test_snippet = &post_snippet[comment_end - 1..];
 414                     let first_newline = test_snippet.find('\n').unwrap_or(test_snippet.len());
 415                     // From the end of the first line of comments.
 416                     let test_snippet = &test_snippet[first_newline..];
 417                     let first = test_snippet
 418                         .find(|c: char| !c.is_whitespace())
 419                         .unwrap_or(test_snippet.len());
 420                     // From the end of the first line of comments to the next non-whitespace char.
 421                     let test_snippet = &test_snippet[..first];
 422
 423                     if test_snippet.chars().filter(|c| c == &'\n').count() > 1 {
 424                         // There were multiple line breaks which got trimmed to nothing.
 425                         new_lines = true;
 426                     }
 427                 }
 428
 429                 // Cleanup post-comment: strip separators and whitespace.
 430                 self.prev_span_end = (self.get_hi)(&item) + BytePos(comment_end as u32);
 431                 let post_snippet = post_snippet[..comment_end].trim();
 432
 433                 let post_snippet_trimmed = if post_snippet.starts_with(',') {
 434                     post_snippet[1..].trim_matches(white_space)
 435                 } else if post_snippet.ends_with(',') {
 436                     post_snippet[..(post_snippet.len() - 1)].trim_matches(white_space)
 437                 } else {
 438                     post_snippet
 439                 };
 440
 441                 let post_comment = if !post_snippet_trimmed.is_empty() {
 442                     Some(post_snippet_trimmed.to_owned())
 443                 } else {
 444                     None
 445                 };
 446
 447                 ListItem {
 448                     pre_comment: pre_comment,
 449                     item: (self.get_item_string)(&item),
 450                     post_comment: post_comment,
 451                     new_lines: new_lines,
 452                 }
 453             })
 454     }
 455 }
 456
 457 // Creates an iterator over a list's items with associated comments.
 458 pub fn itemize_list<'a, T, I, F1, F2, F3>(codemap: &'a CodeMap,
 459                                           inner: I,
 460                                           terminator: &'a str,
 461                                           get_lo: F1,
 462                                           get_hi: F2,
 463                                           get_item_string: F3,
 464                                           prev_span_end: BytePos,
 465                                           next_span_start: BytePos)
 466                                           -> ListItems<'a, I, F1, F2, F3>
 467     where I: Iterator<Item = T>,
 468           F1: Fn(&T) -> BytePos,
 469           F2: Fn(&T) -> BytePos,
 470           F3: Fn(&T) -> Option<String>
 471 {
 472     ListItems {
 473         codemap: codemap,
 474         inner: inner.peekable(),
 475         get_lo: get_lo,
 476         get_hi: get_hi,
 477         get_item_string: get_item_string,
 478         prev_span_end: prev_span_end,
 479         next_span_start: next_span_start,
 480         terminator: terminator,
 481     }
 482 }
 483
 484 fn needs_trailing_separator(separator_tactic: SeparatorTactic,
 485                             list_tactic: DefinitiveListTactic)
 486                             -> bool {
 487     match separator_tactic {
 488         SeparatorTactic::Always => true,
 489         SeparatorTactic::Vertical => list_tactic == DefinitiveListTactic::Vertical,
 490         SeparatorTactic::Never => false,
 491     }
 492 }
 493
 494 /// Returns the count and total width of the list items.
 495 fn calculate_width<I, T>(items: I) -> (usize, usize)
 496     where I: IntoIterator<Item = T>,
 497           T: AsRef<ListItem>
 498 {
 499     items
 500         .into_iter()
 501         .map(|item| total_item_width(item.as_ref()))
 502         .fold((0, 0), |acc, l| (acc.0 + 1, acc.1 + l))
 503 }
 504
 505 fn total_item_width(item: &ListItem) -> usize {
 506     comment_len(item.pre_comment.as_ref().map(|x| &(*x)[..])) +
 507     comment_len(item.post_comment.as_ref().map(|x| &(*x)[..])) +
 508     item.item.as_ref().map_or(0, |str| str.len())
 509 }
 510
 511 fn comment_len(comment: Option<&str>) -> usize {
 512     match comment {
 513         Some(s) => {
 514             let text_len = s.trim().len();
 515             if text_len > 0 {
 516                 // We'll put " /*" before and " */" after inline comments.
 517                 text_len + 6
 518             } else {
 519                 text_len
 520             }
 521         }
 522         None => 0,
 523     }
 524 }
 525
 526 // Compute horizontal and vertical shapes for a struct-lit-like thing.
 527 pub fn struct_lit_shape(shape: Shape,
 528                         context: &RewriteContext,
 529                         prefix_width: usize,
 530                         suffix_width: usize)
 531                         -> Option<(Option<Shape>, Shape)> {
 532     let v_shape = match context.config.struct_lit_style {
 533         IndentStyle::Visual => {
 534             try_opt!(try_opt!(shape.shrink_left(prefix_width)).sub_width(suffix_width))
 535         }
 536         IndentStyle::Block => {
 537             let shape = shape.block_indent(context.config.tab_spaces);
 538             Shape {
 539                 width: try_opt!(context
 540                                     .config
 541                                     .max_width
 542                                     .checked_sub(shape.indent.width())),
 543                 ..shape
 544             }
 545         }
 546     };
 547     let h_shape = shape.sub_width(prefix_width + suffix_width);
 548     Some((h_shape, v_shape))
 549 }
 550
 551 // Compute the tactic for the internals of a struct-lit-like thing.
 552 pub fn struct_lit_tactic(h_shape: Option<Shape>,
 553                          context: &RewriteContext,
 554                          items: &[ListItem])
 555                          -> DefinitiveListTactic {
 556     if let Some(h_shape) = h_shape {
 557         let mut prelim_tactic = match (context.config.struct_lit_style, items.len()) {
 558             (IndentStyle::Visual, 1) => ListTactic::HorizontalVertical,
 559             _ => {
 560                 context
 561                     .config
 562                     .struct_lit_multiline_style
 563                     .to_list_tactic()
 564             }
 565         };
 566
 567         if prelim_tactic == ListTactic::HorizontalVertical && items.len() > 1 {
 568             prelim_tactic = ListTactic::LimitedHorizontalVertical(context.config.struct_lit_width);
 569         }
 570
 571         definitive_tactic(items, prelim_tactic, h_shape.width)
 572     } else {
 573         DefinitiveListTactic::Vertical
 574     }
 575 }
 576
 577 // Given a tactic and possible shapes for horizontal and vertical layout,
 578 // come up with the actual shape to use.
 579 pub fn shape_for_tactic(tactic: DefinitiveListTactic,
 580                         h_shape: Option<Shape>,
 581                         v_shape: Shape)
 582                         -> Shape {
 583     match tactic {
 584         DefinitiveListTactic::Horizontal => h_shape.unwrap(),
 585         _ => v_shape,
 586     }
 587 }
 588
 589 // Create a ListFormatting object for formatting the internals of a
 590 // struct-lit-like thing, that is a series of fields.
 591 pub fn struct_lit_formatting<'a>(shape: Shape,
 592                                  tactic: DefinitiveListTactic,
 593                                  context: &'a RewriteContext,
 594                                  force_no_trailing_comma: bool)
 595                                  -> ListFormatting<'a> {
 596     let ends_with_newline = context.config.struct_lit_style != IndentStyle::Visual &&
 597                             tactic == DefinitiveListTactic::Vertical;
 598     ListFormatting {
 599         tactic: tactic,
 600         separator: ",",
 601         trailing_separator: if force_no_trailing_comma {
 602             SeparatorTactic::Never
 603         } else {
 604             context.config.trailing_comma
 605         },
 606         shape: shape,
 607         ends_with_newline: ends_with_newline,
 608         config: context.config,
 609     }
 610 }