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
  18 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  19 pub enum ListTactic {
  20     // One item per row.
  21     Vertical,
  22     // All items on one row.
  23     Horizontal,
  24     // Try Horizontal layout, if that fails then vertical
  25     HorizontalVertical,
  26     // Pack as many items as possible per row over (possibly) many rows.
  27     Mixed,
  28 }
  29
  30 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
  31 pub enum SeparatorTactic {
  32     Always,
  33     Never,
  34     Vertical,
  35 }
  36
  37 impl_enum_decodable!(SeparatorTactic, Always, Never, Vertical);
  38
  39 // TODO having some helpful ctors for ListFormatting would be nice.
  40 pub struct ListFormatting<'a> {
  41     pub tactic: ListTactic,
  42     pub separator: &'a str,
  43     pub trailing_separator: SeparatorTactic,
  44     pub indent: usize,
  45     // Available width if we layout horizontally.
  46     pub h_width: usize,
  47     // Available width if we layout vertically
  48     pub v_width: usize,
  49     // Non-expressions, e.g. items, will have a new line at the end of the list.
  50     // Important for comment styles.
  51     pub ends_with_newline: bool,
  52 }
  53
  54 pub struct ListItem {
  55     pub pre_comment: Option<String>,
  56     // Item should include attributes and doc comments
  57     pub item: String,
  58     pub post_comment: Option<String>,
  59 }
  60
  61 impl ListItem {
  62     pub fn is_multiline(&self) -> bool {
  63         self.item.contains('\n') || self.pre_comment.is_some() ||
  64         self.post_comment.as_ref().map(|s| s.contains('\n')).unwrap_or(false)
  65     }
  66
  67     pub fn has_line_pre_comment(&self) -> bool {
  68         self.pre_comment.as_ref().map_or(false, |comment| comment.starts_with("//"))
  69     }
  70
  71     pub fn from_str<S: Into<String>>(s: S) -> ListItem {
  72         ListItem { pre_comment: None, item: s.into(), post_comment: None }
  73     }
  74 }
  75
  76 // Format a list of commented items into a string.
  77 // FIXME: this has grown into a monstrosity
  78 // TODO: add unit tests
  79 pub fn write_list<'b>(items: &[ListItem], formatting: &ListFormatting<'b>) -> String {
  80     if items.len() == 0 {
  81         return String::new();
  82     }
  83
  84     let mut tactic = formatting.tactic;
  85
  86     // Conservatively overestimates because of the changing separator tactic.
  87     let sep_count = if formatting.trailing_separator != SeparatorTactic::Never {
  88         items.len()
  89     } else {
  90         items.len() - 1
  91     };
  92     let sep_len = formatting.separator.len();
  93     let total_sep_len = (sep_len + 1) * sep_count;
  94     let total_width = calculate_width(items);
  95     let fits_single = total_width + total_sep_len <= formatting.h_width;
  96
  97     // Check if we need to fallback from horizontal listing, if possible.
  98     if tactic == ListTactic::HorizontalVertical {
  99         debug!("write_list: total_width: {}, total_sep_len: {}, h_width: {}",
 100                total_width, total_sep_len, formatting.h_width);
 101         tactic = if fits_single &&
 102                     !items.iter().any(ListItem::is_multiline) {
 103             ListTactic::Horizontal
 104         } else {
 105             ListTactic::Vertical
 106         };
 107     }
 108
 109     // Check if we can fit everything on a single line in mixed mode.
 110     // The horizontal tactic does not break after v_width columns.
 111     if tactic == ListTactic::Mixed && fits_single {
 112         tactic = ListTactic::Horizontal;
 113     }
 114
 115     // Switch to vertical mode if we find non-block comments.
 116     if items.iter().any(ListItem::has_line_pre_comment) {
 117         tactic = ListTactic::Vertical;
 118     }
 119
 120     // Now that we know how we will layout, we can decide for sure if there
 121     // will be a trailing separator.
 122     let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
 123
 124     // Create a buffer for the result.
 125     // TODO could use a StringBuffer or rope for this
 126     let alloc_width = if tactic == ListTactic::Horizontal {
 127         total_width + total_sep_len
 128     } else {
 129         total_width + items.len() * (formatting.indent + 1)
 130     };
 131     let mut result = String::with_capacity(round_up_to_power_of_two(alloc_width));
 132
 133     let mut line_len = 0;
 134     let indent_str = &make_indent(formatting.indent);
 135     for (i, item) in items.iter().enumerate() {
 136         let first = i == 0;
 137         let last = i == items.len() - 1;
 138         let separate = !last || trailing_separator;
 139         let item_sep_len = if separate { sep_len } else { 0 };
 140         let item_width = item.item.len() + item_sep_len;
 141
 142         match tactic {
 143             ListTactic::Horizontal if !first => {
 144                 result.push(' ');
 145             }
 146             ListTactic::Vertical if !first => {
 147                 result.push('\n');
 148                 result.push_str(indent_str);
 149             }
 150             ListTactic::Mixed => {
 151                 let total_width = total_item_width(item) + item_sep_len;
 152
 153                 if line_len > 0 && line_len + total_width > formatting.v_width {
 154                     result.push('\n');
 155                     result.push_str(indent_str);
 156                     line_len = 0;
 157                 }
 158
 159                 if line_len > 0 {
 160                     result.push(' ');
 161                     line_len += 1;
 162                 }
 163
 164                 line_len += total_width;
 165             }
 166             _ => {}
 167         }
 168
 169         // Pre-comments
 170         if let Some(ref comment) = item.pre_comment {
 171             result.push_str(&rewrite_comment(comment,
 172                                              // Block style in non-vertical mode
 173                                              tactic != ListTactic::Vertical,
 174                                              // Width restriction is only
 175                                              // relevant in vertical mode.
 176                                              formatting.v_width,
 177                                              formatting.indent));
 178
 179             if tactic == ListTactic::Vertical {
 180                 result.push('\n');
 181                 result.push_str(indent_str);
 182             } else {
 183                 result.push(' ');
 184             }
 185         }
 186
 187         result.push_str(&item.item);
 188
 189         // Post-comments
 190         if tactic != ListTactic::Vertical && item.post_comment.is_some() {
 191             let formatted_comment = rewrite_comment(item.post_comment.as_ref().unwrap(),
 192                                                     true,
 193                                                     formatting.v_width,
 194                                                     0);
 195
 196             result.push(' ');
 197             result.push_str(&formatted_comment);
 198         }
 199
 200         if separate {
 201             result.push_str(formatting.separator);
 202         }
 203
 204         if tactic == ListTactic::Vertical && item.post_comment.is_some() {
 205             // 1 = space between item and comment.
 206             let width = formatting.v_width.checked_sub(item_width + 1).unwrap_or(1);
 207             let offset = formatting.indent + item_width + 1;
 208             let comment = item.post_comment.as_ref().unwrap();
 209             // Use block-style only for the last item or multiline comments.
 210             let block_style = formatting.ends_with_newline && last ||
 211                               comment.trim().contains('\n') ||
 212                               comment.trim().len() > width;
 213
 214             let formatted_comment = rewrite_comment(comment, block_style, width, offset);
 215
 216             result.push(' ');
 217             result.push_str(&formatted_comment);
 218         }
 219     }
 220
 221     result
 222 }
 223
 224 // Turns a list into a vector of items with associated comments.
 225 // TODO: we probably do not want to take a terminator any more. Instead, we
 226 // should demand a proper span end.
 227 pub fn itemize_list<T, I, F1, F2, F3>(codemap: &CodeMap,
 228                                       prefix: Vec<ListItem>,
 229                                       it: I,
 230                                       separator: &str,
 231                                       terminator: &str,
 232                                       get_lo: F1,
 233                                       get_hi: F2,
 234                                       get_item_string: F3,
 235                                       mut prev_span_end: BytePos,
 236                                       next_span_start: BytePos)
 237                                       -> Vec<ListItem>
 238     where I: Iterator<Item = T>,
 239           F1: Fn(&T) -> BytePos,
 240           F2: Fn(&T) -> BytePos,
 241           F3: Fn(&T) -> String
 242 {
 243     let mut result = prefix;
 244     result.reserve(it.size_hint().0);
 245
 246     let mut new_it = it.peekable();
 247     let white_space: &[_] = &[' ', '\t'];
 248
 249     while let Some(item) = new_it.next() {
 250         // Pre-comment
 251         let pre_snippet = codemap.span_to_snippet(codemap::mk_sp(prev_span_end,
 252                                                                 get_lo(&item)))
 253                                  .unwrap();
 254         let pre_snippet = pre_snippet.trim();
 255         let pre_comment = if pre_snippet.len() > 0 {
 256             Some(pre_snippet.to_owned())
 257         } else {
 258             None
 259         };
 260
 261         // Post-comment
 262         let next_start = match new_it.peek() {
 263             Some(ref next_item) => get_lo(next_item),
 264             None => next_span_start
 265         };
 266         let post_snippet = codemap.span_to_snippet(codemap::mk_sp(get_hi(&item),
 267                                                                   next_start))
 268                                   .unwrap();
 269
 270         let comment_end = match new_it.peek() {
 271             Some(..) => {
 272                 let block_open_index = post_snippet.find("/*");
 273                 let newline_index = post_snippet.find('\n');
 274                 let separator_index = post_snippet.find_uncommented(separator).unwrap();
 275
 276                 match (block_open_index, newline_index) {
 277                     // Separator before comment, with the next item on same line.
 278                     // Comment belongs to next item.
 279                     (Some(i), None) if i > separator_index => { separator_index + separator.len() }
 280                     // Block-style post-comment before the separator.
 281                     (Some(i), None) => {
 282                         cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 283                                  separator_index + separator.len())
 284                     }
 285                     // Block-style post-comment. Either before or after the separator.
 286                     (Some(i), Some(j)) if i < j => {
 287                         cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
 288                                  separator_index + separator.len())
 289                     }
 290                     // Potential *single* line comment.
 291                     (_, Some(j)) => { j + 1 }
 292                     _ => post_snippet.len()
 293                 }
 294             },
 295             None => {
 296                 post_snippet.find_uncommented(terminator)
 297                             .unwrap_or(post_snippet.len())
 298             }
 299         };
 300
 301         // Cleanup post-comment: strip separators and whitespace.
 302         prev_span_end = get_hi(&item) + BytePos(comment_end as u32);
 303         let mut post_snippet = post_snippet[..comment_end].trim();
 304
 305         if post_snippet.starts_with(separator) {
 306             post_snippet = post_snippet[separator.len()..]
 307                 .trim_matches(white_space);
 308         } else if post_snippet.ends_with(separator) {
 309             post_snippet = post_snippet[..post_snippet.len()-separator.len()]
 310                 .trim_matches(white_space);
 311         }
 312
 313         result.push(ListItem {
 314             pre_comment: pre_comment,
 315             item: get_item_string(&item),
 316             post_comment: if post_snippet.len() > 0 {
 317                 Some(post_snippet.to_owned())
 318             } else {
 319                 None
 320             }
 321         });
 322     }
 323
 324     result
 325 }
 326
 327 fn needs_trailing_separator(separator_tactic: SeparatorTactic, list_tactic: ListTactic) -> bool {
 328     match separator_tactic {
 329         SeparatorTactic::Always => true,
 330         SeparatorTactic::Vertical => list_tactic == ListTactic::Vertical,
 331         SeparatorTactic::Never => false,
 332     }
 333 }
 334
 335 fn calculate_width(items: &[ListItem]) -> usize {
 336     items.iter().map(total_item_width).fold(0, |a, l| a + l)
 337 }
 338
 339 fn total_item_width(item: &ListItem) -> usize {
 340     comment_len(&item.pre_comment) + comment_len(&item.post_comment) + item.item.len()
 341 }
 342
 343 fn comment_len(comment: &Option<String>) -> usize {
 344     match comment {
 345         &Some(ref s) => {
 346             let text_len = s.trim().len();
 347             if text_len > 0 {
 348                 // We'll put " /*" before and " */" after inline comments.
 349                 text_len + 6
 350             } else {
 351                 text_len
 352             }
 353         },
 354         &None => 0
 355     }
 356 }