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