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