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