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 is_expression: 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                                              1000,
 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             // We'll assume it'll fit on one line at this point
 192             let formatted_comment = rewrite_comment(item.post_comment.as_ref().unwrap(),
 193                                                     true,
 194                                                     1000,
 195                                                     0);
 196
 197             result.push(' ');
 198             result.push_str(&formatted_comment);
 199         }
 200
 201         if separate {
 202             result.push_str(formatting.separator);
 203         }
 204
 205         if tactic == ListTactic::Vertical && item.post_comment.is_some() {
 206             let width = formatting.v_width - item_width - 1; // Space between item and comment
 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.is_expression && last ||
 211                               comment.trim().contains('\n') ||
 212                               comment.trim().len() > width;
 213
 214             let formatted_comment = rewrite_comment(comment,
 215                                                     block_style,
 216                                                     width,
 217                                                     offset);
 218
 219             result.push(' ');
 220             result.push_str(&formatted_comment);
 221         }
 222     }
 223
 224     result
 225 }
 226
 227 fn has_line_pre_comment(item: &ListItem) -> bool {
 228     match item.pre_comment {
 229         Some(ref comment) => comment.starts_with("//"),
 230         None => false
 231     }
 232 }
 233
 234 // Turns a list into a vector of items with associated comments.
 235 // TODO: we probably do not want to take a terminator any more. Instead, we
 236 // should demand a proper span end.
 237 pub fn itemize_list<T, I, F1, F2, F3>(codemap: &CodeMap,
 238                                       prefix: Vec<ListItem>,
 239                                       it: I,
 240                                       separator: &str,
 241                                       terminator: &str,
 242                                       get_lo: F1,
 243                                       get_hi: F2,
 244                                       get_item: F3,
 245                                       mut prev_span_end: BytePos,
 246                                       next_span_start: BytePos)
 247     -> Vec<ListItem>
 248     where I: Iterator<Item=T>,
 249           F1: Fn(&T) -> BytePos,
 250           F2: Fn(&T) -> BytePos,
 251           F3: Fn(&T) -> String
 252 {
 253     let mut result = prefix;
 254     let mut new_it = it.peekable();
 255     let white_space: &[_] = &[' ', '\t'];
 256
 257     while let Some(item) = new_it.next() {
 258         // Pre-comment
 259         let pre_snippet = codemap.span_to_snippet(codemap::mk_sp(prev_span_end,
 260                                                                 get_lo(&item)))
 261                                  .unwrap();
 262         let pre_snippet = pre_snippet.trim();
 263         let pre_comment = if pre_snippet.len() > 0 {
 264             Some(pre_snippet.to_owned())
 265         } else {
 266             None
 267         };
 268
 269         // Post-comment
 270         let next_start = match new_it.peek() {
 271             Some(ref next_item) => get_lo(next_item),
 272             None => next_span_start
 273         };
 274         let post_snippet = codemap.span_to_snippet(codemap::mk_sp(get_hi(&item),
 275                                                                   next_start))
 276                                   .unwrap();
 277
 278         let comment_end = match new_it.peek() {
 279             Some(..) => {
 280                 if let Some(start) = before(&post_snippet, "/*", "\n") {
 281                     // Block-style post-comment. Either before or after the separator.
 282                     cmp::max(find_comment_end(&post_snippet[start..]).unwrap() + start,
 283                              post_snippet.find_uncommented(separator).unwrap() + separator.len())
 284                 } else if let Some(idx) = post_snippet.find('\n') {
 285                     idx + 1
 286                 } else {
 287                     post_snippet.len()
 288                 }
 289             },
 290             None => {
 291                 post_snippet.find_uncommented(terminator)
 292                             .unwrap_or(post_snippet.len())
 293             }
 294         };
 295
 296         prev_span_end = get_hi(&item) + BytePos(comment_end as u32);
 297         let mut post_snippet = post_snippet[..comment_end].trim();
 298
 299         if post_snippet.starts_with(separator) {
 300             post_snippet = post_snippet[separator.len()..]
 301                 .trim_matches(white_space);
 302         } else if post_snippet.ends_with(separator) {
 303             post_snippet = post_snippet[..post_snippet.len()-separator.len()]
 304                 .trim_matches(white_space);
 305         }
 306
 307         result.push(ListItem {
 308             pre_comment: pre_comment,
 309             item: get_item(&item),
 310             post_comment: if post_snippet.len() > 0 {
 311                 Some(post_snippet.to_owned())
 312             } else {
 313                 None
 314             }
 315         });
 316     }
 317
 318     result
 319 }
 320
 321 fn needs_trailing_separator(separator_tactic: SeparatorTactic, list_tactic: ListTactic) -> bool {
 322     match separator_tactic {
 323         SeparatorTactic::Always => true,
 324         SeparatorTactic::Vertical => list_tactic == ListTactic::Vertical,
 325         SeparatorTactic::Never => false,
 326     }
 327 }
 328
 329 fn calculate_width(items: &[ListItem]) -> usize {
 330     items.iter().map(total_item_width).fold(0, |a, l| a + l)
 331 }
 332
 333 fn total_item_width(item: &ListItem) -> usize {
 334     comment_len(&item.pre_comment) + comment_len(&item.post_comment) + item.item.len()
 335 }
 336
 337 fn comment_len(comment: &Option<String>) -> usize {
 338     match comment {
 339         &Some(ref s) => {
 340             let text_len = s.trim().len();
 341             if text_len > 0 {
 342                 // We'll put " /*" before and " */" after inline comments.
 343                 text_len + 6
 344             } else {
 345                 text_len
 346             }
 347         },
 348         &None => 0
 349     }
 350 }