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
  13 use syntax::codemap::{self, CodeMap, BytePos};
  14
  15 use utils::{round_up_to_power_of_two, make_indent};
  16 use comment::{FindUncommented, rewrite_comment, find_comment_end};
  17 use string::before;
  18
  19 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  20 pub enum ListTactic {
  21     // One item per row.
  22     Vertical,
  23     // All items on one row.
  24     Horizontal,
  25     // Try Horizontal layout, if that fails then vertical
  26     HorizontalVertical,
  27     // Pack as many items as possible per row over (possibly) many rows.
  28     Mixed,
  29 }
  30
  31 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  32 pub enum SeparatorTactic {
  33     Always,
  34     Never,
  35     Vertical,
  36 }
  37
  38 impl_enum_decodable!(SeparatorTactic, Always, Never, Vertical);
  39
  40 // TODO having some helpful ctors for ListFormatting would be nice.
  41 pub struct ListFormatting<'a> {
  42     pub tactic: ListTactic,
  43     pub separator: &'a str,
  44     pub trailing_separator: SeparatorTactic,
  45     pub indent: usize,
  46     // Available width if we layout horizontally.
  47     pub h_width: usize,
  48     // Available width if we layout vertically
  49     pub v_width: usize,
  50     // Non-expressions, e.g. items, will have a new line at the end of the list.
  51     // Important for comment styles.
  52     pub ends_with_newline: bool
  53 }
  54
  55 pub struct ListItem {
  56     pub pre_comment: Option<String>,
  57     // Item should include attributes and doc comments
  58     pub item: String,
  59     pub post_comment: Option<String>
  60 }
  61
  62 impl ListItem {
  63     pub fn is_multiline(&self) -> bool {
  64         self.item.contains('\n') ||
  65         self.pre_comment.is_some() ||
  66         self.post_comment.as_ref().map(|s| s.contains('\n')).unwrap_or(false)
  67     }
  68
  69     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
  70         ListItem {
  71             pre_comment: None,
  72             item: s.into(),
  73             post_comment: None
  74         }
  75     }
  76 }
  77
  78 // Format a list of commented items into a string.
  79 // FIXME: this has grown into a monstrosity
  80 // TODO: add unit tests
  81 pub fn write_list<'b>(items: &[ListItem], formatting: &ListFormatting<'b>) -> String {
  82     if items.len() == 0 {
  83         return String::new();
  84     }
  85
  86     let mut tactic = formatting.tactic;
  87
  88     // Conservatively overestimates because of the changing separator tactic.
  89     let sep_count = if formatting.trailing_separator != SeparatorTactic::Never {
  90         items.len()
  91     } else {
  92         items.len() - 1
  93     };
  94     let sep_len = formatting.separator.len();
  95     let total_sep_len = (sep_len + 1) * sep_count;
  96     let total_width = calculate_width(items);
  97     let fits_single = total_width + total_sep_len <= formatting.h_width;
  98
  99     // Check if we need to fallback from horizontal listing, if possible.
 100     if tactic == ListTactic::HorizontalVertical {
 101         debug!("write_list: total_width: {}, total_sep_len: {}, h_width: {}",
 102                total_width, total_sep_len, formatting.h_width);
 103         tactic = if fits_single &&
 104                     !items.iter().any(ListItem::is_multiline) {
 105             ListTactic::Horizontal
 106         } else {
 107             ListTactic::Vertical
 108         };
 109     }
 110
 111     // Check if we can fit everything on a single line in mixed mode.
 112     // The horizontal tactic does not break after v_width columns.
 113     if tactic == ListTactic::Mixed && fits_single {
 114         tactic = ListTactic::Horizontal;
 115     }
 116
 117     // Switch to vertical mode if we find non-block comments.
 118     if items.iter().any(has_line_pre_comment) {
 119         tactic = ListTactic::Vertical;
 120     }
 121
 122     // Now that we know how we will layout, we can decide for sure if there
 123     // will be a trailing separator.
 124     let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
 125
 126     // Create a buffer for the result.
 127     // TODO could use a StringBuffer or rope for this
 128     let alloc_width = if tactic == ListTactic::Horizontal {
 129         total_width + total_sep_len
 130     } else {
 131         total_width + items.len() * (formatting.indent + 1)
 132     };
 133     let mut result = String::with_capacity(round_up_to_power_of_two(alloc_width));
 134
 135     let mut line_len = 0;
 136     let indent_str = &make_indent(formatting.indent);
 137     for (i, item) in items.iter().enumerate() {
 138         let first = i == 0;
 139         let last = i == items.len() - 1;
 140         let separate = !last || trailing_separator;
 141         let item_sep_len = if separate { sep_len } else { 0 };
 142         let item_width = item.item.len() + item_sep_len;
 143
 144         match tactic {
 145             ListTactic::Horizontal if !first => {
 146                 result.push(' ');
 147             }
 148             ListTactic::Vertical if !first => {
 149                 result.push('\n');
 150                 result.push_str(indent_str);
 151             }
 152             ListTactic::Mixed => {
 153                 let total_width = total_item_width(item) + item_sep_len;
 154
 155                 if line_len > 0 && line_len + total_width > formatting.v_width {
 156                     result.push('\n');
 157                     result.push_str(indent_str);
 158                     line_len = 0;
 159                 }
 160
 161                 if line_len > 0 {
 162                     result.push(' ');
 163                     line_len += 1;
 164                 }
 165
 166                 line_len += total_width;
 167             }
 168             _ => {}
 169         }
 170
 171         // Pre-comments
 172         if let Some(ref comment) = item.pre_comment {
 173             result.push_str(&rewrite_comment(comment,
 174                                              // Block style in non-vertical mode
 175                                              tactic != ListTactic::Vertical,
 176                                              // Width restriction is only
 177                                              // relevant in vertical mode.
 178                                              formatting.v_width,
 179                                              formatting.indent));
 180
 181             if tactic == ListTactic::Vertical {
 182                 result.push('\n');
 183                 result.push_str(indent_str);
 184             } else {
 185                 result.push(' ');
 186             }
 187         }
 188
 189         result.push_str(&item.item);
 190
 191         // Post-comments
 192         if tactic != ListTactic::Vertical && item.post_comment.is_some() {
 193             let formatted_comment = rewrite_comment(item.post_comment.as_ref().unwrap(),
 194                                                     true,
 195                                                     formatting.v_width,
 196                                                     0);
 197
 198             result.push(' ');
 199             result.push_str(&formatted_comment);
 200         }
 201
 202         if separate {
 203             result.push_str(formatting.separator);
 204         }
 205
 206         if tactic == ListTactic::Vertical && item.post_comment.is_some() {
 207             // 1 = space between item and comment.
 208             let width = formatting.v_width.checked_sub(item_width + 1).unwrap_or(1);
 209             let offset = formatting.indent + item_width + 1;
 210             let comment = item.post_comment.as_ref().unwrap();
 211             // Use block-style only for the last item or multiline comments.
 212             let block_style = formatting.ends_with_newline && last ||
 213                               comment.trim().contains('\n') ||
 214                               comment.trim().len() > width;
 215
 216             let formatted_comment = rewrite_comment(comment, block_style, width, offset);
 217
 218             result.push(' ');
 219             result.push_str(&formatted_comment);
 220         }
 221     }
 222
 223     result
 224 }
 225
 226 fn has_line_pre_comment(item: &ListItem) -> bool {
 227     match item.pre_comment {
 228         Some(ref comment) => comment.starts_with("//"),
 229         None => false
 230     }
 231 }
 232
 233 // Turns a list into a vector of items with associated comments.
 234 // TODO: we probably do not want to take a terminator any more. Instead, we
 235 // should demand a proper span end.
 236 pub fn itemize_list<T, I, F1, F2, F3>(codemap: &CodeMap,
 237                                       prefix: Vec<ListItem>,
 238                                       it: I,
 239                                       separator: &str,
 240                                       terminator: &str,
 241                                       get_lo: F1,
 242                                       get_hi: F2,
 243                                       get_item_string: F3,
 244                                       mut prev_span_end: BytePos,
 245                                       next_span_start: BytePos)
 246     -> Vec<ListItem>
 247     where I: Iterator<Item=T>,
 248           F1: Fn(&T) -> BytePos,
 249           F2: Fn(&T) -> BytePos,
 250           F3: Fn(&T) -> String
 251 {
 252     let mut result = prefix;
 253     let mut new_it = it.peekable();
 254     let white_space: &[_] = &[' ', '\t'];
 255
 256     while let Some(item) = new_it.next() {
 257         // Pre-comment
 258         let pre_snippet = codemap.span_to_snippet(codemap::mk_sp(prev_span_end,
 259                                                                 get_lo(&item)))
 260                                  .unwrap();
 261         let pre_snippet = pre_snippet.trim();
 262         let pre_comment = if pre_snippet.len() > 0 {
 263             Some(pre_snippet.to_owned())
 264         } else {
 265             None
 266         };
 267
 268         // Post-comment
 269         let next_start = match new_it.peek() {
 270             Some(ref next_item) => get_lo(next_item),
 271             None => next_span_start
 272         };
 273         let post_snippet = codemap.span_to_snippet(codemap::mk_sp(get_hi(&item),
 274                                                                   next_start))
 275                                   .unwrap();
 276
 277         let comment_end = match new_it.peek() {
 278             Some(..) => {
 279                 if let Some(start) = before(&post_snippet, "/*", "\n") {
 280                     // Block-style post-comment. Either before or after the separator.
 281                     cmp::max(find_comment_end(&post_snippet[start..]).unwrap() + start,
 282                              post_snippet.find_uncommented(separator).unwrap() + separator.len())
 283                 } else if let Some(idx) = post_snippet.find('\n') {
 284                     idx + 1
 285                 } else {
 286                     post_snippet.len()
 287                 }
 288             },
 289             None => {
 290                 post_snippet.find_uncommented(terminator)
 291                             .unwrap_or(post_snippet.len())
 292             }
 293         };
 294
 295         prev_span_end = get_hi(&item) + BytePos(comment_end as u32);
 296         let mut post_snippet = post_snippet[..comment_end].trim();
 297
 298         if post_snippet.starts_with(separator) {
 299             post_snippet = post_snippet[separator.len()..]
 300                 .trim_matches(white_space);
 301         } else if post_snippet.ends_with(separator) {
 302             post_snippet = post_snippet[..post_snippet.len()-separator.len()]
 303                 .trim_matches(white_space);
 304         }
 305
 306         result.push(ListItem {
 307             pre_comment: pre_comment,
 308             item: get_item_string(&item),
 309             post_comment: if post_snippet.len() > 0 {
 310                 Some(post_snippet.to_owned())
 311             } else {
 312                 None
 313             }
 314         });
 315     }
 316
 317     result
 318 }
 319
 320 fn needs_trailing_separator(separator_tactic: SeparatorTactic, list_tactic: ListTactic) -> bool {
 321     match separator_tactic {
 322         SeparatorTactic::Always => true,
 323         SeparatorTactic::Vertical => list_tactic == ListTactic::Vertical,
 324         SeparatorTactic::Never => false,
 325     }
 326 }
 327
 328 fn calculate_width(items: &[ListItem]) -> usize {
 329     items.iter().map(total_item_width).fold(0, |a, l| a + l)
 330 }
 331
 332 fn total_item_width(item: &ListItem) -> usize {
 333     comment_len(&item.pre_comment) + comment_len(&item.post_comment) + item.item.len()
 334 }
 335
 336 fn comment_len(comment: &Option<String>) -> usize {
 337     match comment {
 338         &Some(ref s) => {
 339             let text_len = s.trim().len();
 340             if text_len > 0 {
 341                 // We'll put " /*" before and " */" after inline comments.
 342                 text_len + 6
 343             } else {
 344                 text_len
 345             }
 346         },
 347         &None => 0
 348     }
 349 }