src/missed_spans.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 config::WriteMode;
  12 use visitor::FmtVisitor;
  13 use syntax::codemap::{self, BytePos, Span, Pos};
  14 use comment::{CodeCharKind, CommentCodeSlices, rewrite_comment};
  15
  16 impl<'a> FmtVisitor<'a> {
  17     fn output_at_start(&self) -> bool {
  18         self.buffer.len == 0
  19     }
  20
  21     // TODO these format_missing methods are ugly. Refactor and add unit tests
  22     // for the central whitespace stripping loop.
  23     pub fn format_missing(&mut self, end: BytePos) {
  24         self.format_missing_inner(end,
  25                                   |this, last_snippet, _| this.buffer.push_str(last_snippet))
  26     }
  27
  28     pub fn format_missing_with_indent(&mut self, end: BytePos) {
  29         let config = self.config;
  30         self.format_missing_inner(end, |this, last_snippet, snippet| {
  31             this.buffer.push_str(last_snippet.trim_right());
  32             if last_snippet == snippet && !this.output_at_start() {
  33                 // No new lines in the snippet.
  34                 this.buffer.push_str("\n");
  35             }
  36             let indent = this.block_indent.to_string(config);
  37             this.buffer.push_str(&indent);
  38         })
  39     }
  40
  41     fn format_missing_inner<F: Fn(&mut FmtVisitor, &str, &str)>(&mut self,
  42                                                                 end: BytePos,
  43                                                                 process_last_snippet: F) {
  44         let start = self.last_pos;
  45
  46         if start == end {
  47             // Do nothing if this is the beginning of the file.
  48             if !self.output_at_start() {
  49                 process_last_snippet(self, "", "");
  50             }
  51             return;
  52         }
  53
  54         assert!(start < end,
  55                 "Request to format inverted span: {:?} to {:?}",
  56                 self.codemap.lookup_char_pos(start),
  57                 self.codemap.lookup_char_pos(end));
  58
  59         self.last_pos = end;
  60         let span = codemap::mk_sp(start, end);
  61
  62         self.write_snippet(span, &process_last_snippet);
  63     }
  64
  65     fn write_snippet<F>(&mut self, span: Span, process_last_snippet: F)
  66         where F: Fn(&mut FmtVisitor, &str, &str)
  67     {
  68         // Get a snippet from the file start to the span's hi without allocating.
  69         // We need it to determine what precedes the current comment. If the comment
  70         // follows code on the same line, we won't touch it.
  71         let big_span_lo = self.codemap.lookup_char_pos(span.lo).file.start_pos;
  72         let local_begin = self.codemap.lookup_byte_offset(big_span_lo);
  73         let local_end = self.codemap.lookup_byte_offset(span.hi);
  74         let start_index = local_begin.pos.to_usize();
  75         let end_index = local_end.pos.to_usize();
  76         let big_snippet = &local_begin.fm.src.as_ref().unwrap()[start_index..end_index];
  77
  78         let big_diff = (span.lo - big_span_lo).to_usize();
  79         let snippet = self.snippet(span);
  80
  81         self.write_snippet_inner(big_snippet, big_diff, &snippet, process_last_snippet);
  82     }
  83
  84     fn write_snippet_inner<F>(&mut self,
  85                               big_snippet: &str,
  86                               big_diff: usize,
  87                               old_snippet: &str,
  88                               process_last_snippet: F)
  89         where F: Fn(&mut FmtVisitor, &str, &str)
  90     {
  91         // Trim whitespace from the right hand side of each line.
  92         // Annoyingly, the library functions for splitting by lines etc. are not
  93         // quite right, so we must do it ourselves.
  94         let mut line_start = 0;
  95         let mut last_wspace = None;
  96         let mut rewrite_next_comment = true;
  97
  98         fn replace_chars(string: &str) -> String {
  99             string.chars()
 100                 .map(|ch| { if ch.is_whitespace() { ch } else { 'X' } })
 101                 .collect()
 102         }
 103
 104         let replaced = match self.config.write_mode {
 105             WriteMode::Coverage => replace_chars(old_snippet),
 106             _ => old_snippet.to_owned(),
 107         };
 108         let snippet = &*replaced;
 109
 110         for (kind, offset, subslice) in CommentCodeSlices::new(snippet) {
 111             if let CodeCharKind::Comment = kind {
 112                 let last_char = big_snippet[..(offset + big_diff)]
 113                     .chars()
 114                     .rev()
 115                     .skip_while(|rev_c| [' ', '\t'].contains(&rev_c))
 116                     .next();
 117
 118                 let fix_indent = last_char.map_or(true, |rev_c| ['{', '\n'].contains(&rev_c));
 119
 120                 if rewrite_next_comment && fix_indent {
 121                     if let Some('{') = last_char {
 122                         self.buffer.push_str("\n");
 123                     }
 124
 125                     let comment_width = ::std::cmp::min(self.config.ideal_width,
 126                                                         self.config.max_width -
 127                                                         self.block_indent.width());
 128
 129                     self.buffer.push_str(&self.block_indent.to_string(self.config));
 130                     self.buffer.push_str(&rewrite_comment(subslice,
 131                                                           false,
 132                                                           comment_width,
 133                                                           self.block_indent,
 134                                                           self.config)
 135                         .unwrap());
 136
 137                     last_wspace = None;
 138                     line_start = offset + subslice.len();
 139
 140                     if let Some('/') = subslice.chars().skip(1).next() {
 141                         // Add a newline after line comments
 142                         self.buffer.push_str("\n");
 143                     } else if line_start <= snippet.len() {
 144                         // For other comments add a newline if there isn't one at the end already
 145                         match snippet[line_start..].chars().next() {
 146                             Some('\n') | Some('\r') => (),
 147                             _ => self.buffer.push_str("\n"),
 148                         }
 149                     }
 150
 151                     continue;
 152                 } else {
 153                     rewrite_next_comment = false;
 154                 }
 155             }
 156
 157             for (mut i, c) in subslice.char_indices() {
 158                 i += offset;
 159
 160                 if c == '\n' {
 161                     if let Some(lw) = last_wspace {
 162                         self.buffer.push_str(&snippet[line_start..lw]);
 163                         self.buffer.push_str("\n");
 164                     } else {
 165                         self.buffer.push_str(&snippet[line_start..i + 1]);
 166                     }
 167
 168                     line_start = i + 1;
 169                     last_wspace = None;
 170                     rewrite_next_comment = rewrite_next_comment || kind == CodeCharKind::Normal;
 171                 } else {
 172                     if c.is_whitespace() {
 173                         if last_wspace.is_none() {
 174                             last_wspace = Some(i);
 175                         }
 176                     } else {
 177                         rewrite_next_comment = rewrite_next_comment || kind == CodeCharKind::Normal;
 178                         last_wspace = None;
 179                     }
 180                 }
 181             }
 182         }
 183
 184         process_last_snippet(self, &snippet[line_start..], &snippet);
 185     }
 186 }