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