src/vertical.rs

   1 // Copyright 2017 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 // Format with vertical alignment.
  12
  13 use std::cmp;
  14
  15 use config::lists::*;
  16 use syntax::ast;
  17 use syntax::codemap::{BytePos, Span};
  18
  19 use codemap::SpanUtils;
  20 use comment::{combine_strs_with_missing_comments, contains_comment};
  21 use expr::rewrite_field;
  22 use items::{rewrite_struct_field, rewrite_struct_field_prefix};
  23 use lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  24 use rewrite::{Rewrite, RewriteContext};
  25 use shape::{Indent, Shape};
  26 use spanned::Spanned;
  27 use utils::{contains_skip, is_attributes_extendable, mk_sp, rewrite_ident};
  28
  29 pub trait AlignedItem {
  30     fn skip(&self) -> bool;
  31     fn get_span(&self) -> Span;
  32     fn rewrite_prefix(&self, context: &RewriteContext, shape: Shape) -> Option<String>;
  33     fn rewrite_aligned_item(
  34         &self,
  35         context: &RewriteContext,
  36         shape: Shape,
  37         prefix_max_width: usize,
  38     ) -> Option<String>;
  39 }
  40
  41 impl AlignedItem for ast::StructField {
  42     fn skip(&self) -> bool {
  43         contains_skip(&self.attrs)
  44     }
  45
  46     fn get_span(&self) -> Span {
  47         self.span()
  48     }
  49
  50     fn rewrite_prefix(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  51         let attrs_str = self.attrs.rewrite(context, shape)?;
  52         let missing_span = if self.attrs.is_empty() {
  53             mk_sp(self.span.lo(), self.span.lo())
  54         } else {
  55             mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
  56         };
  57         let attrs_extendable = self.ident.is_none() && is_attributes_extendable(&attrs_str);
  58         rewrite_struct_field_prefix(context, self).and_then(|field_str| {
  59             combine_strs_with_missing_comments(
  60                 context,
  61                 &attrs_str,
  62                 &field_str,
  63                 missing_span,
  64                 shape,
  65                 attrs_extendable,
  66             )
  67         })
  68     }
  69
  70     fn rewrite_aligned_item(
  71         &self,
  72         context: &RewriteContext,
  73         shape: Shape,
  74         prefix_max_width: usize,
  75     ) -> Option<String> {
  76         rewrite_struct_field(context, self, shape, prefix_max_width)
  77     }
  78 }
  79
  80 impl AlignedItem for ast::Field {
  81     fn skip(&self) -> bool {
  82         contains_skip(&self.attrs)
  83     }
  84
  85     fn get_span(&self) -> Span {
  86         self.span()
  87     }
  88
  89     fn rewrite_prefix(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  90         let attrs_str = self.attrs.rewrite(context, shape)?;
  91         let name = rewrite_ident(context, self.ident);
  92         let missing_span = if self.attrs.is_empty() {
  93             mk_sp(self.span.lo(), self.span.lo())
  94         } else {
  95             mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
  96         };
  97         combine_strs_with_missing_comments(
  98             context,
  99             &attrs_str,
 100             name,
 101             missing_span,
 102             shape,
 103             is_attributes_extendable(&attrs_str),
 104         )
 105     }
 106
 107     fn rewrite_aligned_item(
 108         &self,
 109         context: &RewriteContext,
 110         shape: Shape,
 111         prefix_max_width: usize,
 112     ) -> Option<String> {
 113         rewrite_field(context, self, shape, prefix_max_width)
 114     }
 115 }
 116
 117 pub fn rewrite_with_alignment<T: AlignedItem>(
 118     fields: &[T],
 119     context: &RewriteContext,
 120     shape: Shape,
 121     span: Span,
 122     one_line_width: usize,
 123 ) -> Option<String> {
 124     let (spaces, group_index) = if context.config.struct_field_align_threshold() > 0 {
 125         group_aligned_items(context, fields)
 126     } else {
 127         ("", fields.len() - 1)
 128     };
 129     let init = &fields[0..group_index + 1];
 130     let rest = &fields[group_index + 1..];
 131     let init_last_pos = if rest.is_empty() {
 132         span.hi()
 133     } else {
 134         // Decide whether the missing comments should stick to init or rest.
 135         let init_hi = init[init.len() - 1].get_span().hi();
 136         let rest_lo = rest[0].get_span().lo();
 137         let missing_span = mk_sp(init_hi, rest_lo);
 138         let missing_span = mk_sp(
 139             context.snippet_provider.span_after(missing_span, ","),
 140             missing_span.hi(),
 141         );
 142
 143         let snippet = context.snippet(missing_span);
 144         if snippet.trim_left().starts_with("//") {
 145             let offset = snippet.lines().next().map_or(0, |l| l.len());
 146             // 2 = "," + "\n"
 147             init_hi + BytePos(offset as u32 + 2)
 148         } else if snippet.trim_left().starts_with("/*") {
 149             let comment_lines = snippet
 150                 .lines()
 151                 .position(|line| line.trim_right().ends_with("*/"))
 152                 .unwrap_or(0);
 153
 154             let offset = snippet
 155                 .lines()
 156                 .take(comment_lines + 1)
 157                 .collect::<Vec<_>>()
 158                 .join("\n")
 159                 .len();
 160
 161             init_hi + BytePos(offset as u32 + 2)
 162         } else {
 163             missing_span.lo()
 164         }
 165     };
 166     let init_span = mk_sp(span.lo(), init_last_pos);
 167     let one_line_width = if rest.is_empty() { one_line_width } else { 0 };
 168     let result =
 169         rewrite_aligned_items_inner(context, init, init_span, shape.indent, one_line_width)?;
 170     if rest.is_empty() {
 171         Some(result + spaces)
 172     } else {
 173         let rest_span = mk_sp(init_last_pos, span.hi());
 174         let rest_str = rewrite_with_alignment(rest, context, shape, rest_span, one_line_width)?;
 175         Some(
 176             result
 177                 + spaces
 178                 + "\n"
 179                 + &shape
 180                     .indent
 181                     .block_indent(context.config)
 182                     .to_string(context.config)
 183                 + &rest_str,
 184         )
 185     }
 186 }
 187
 188 fn struct_field_prefix_max_min_width<T: AlignedItem>(
 189     context: &RewriteContext,
 190     fields: &[T],
 191     shape: Shape,
 192 ) -> (usize, usize) {
 193     fields
 194         .iter()
 195         .map(|field| {
 196             field.rewrite_prefix(context, shape).and_then(|field_str| {
 197                 if field_str.contains('\n') {
 198                     None
 199                 } else {
 200                     Some(field_str.len())
 201                 }
 202             })
 203         }).fold(Some((0, ::std::usize::MAX)), |acc, len| match (acc, len) {
 204             (Some((max_len, min_len)), Some(len)) => {
 205                 Some((cmp::max(max_len, len), cmp::min(min_len, len)))
 206             }
 207             _ => None,
 208         }).unwrap_or((0, 0))
 209 }
 210
 211 fn rewrite_aligned_items_inner<T: AlignedItem>(
 212     context: &RewriteContext,
 213     fields: &[T],
 214     span: Span,
 215     offset: Indent,
 216     one_line_width: usize,
 217 ) -> Option<String> {
 218     let item_indent = offset.block_indent(context.config);
 219     // 1 = ","
 220     let item_shape = Shape::indented(item_indent, context.config).sub_width(1)?;
 221     let (mut field_prefix_max_width, field_prefix_min_width) =
 222         struct_field_prefix_max_min_width(context, fields, item_shape);
 223     let max_diff = field_prefix_max_width.saturating_sub(field_prefix_min_width);
 224     if max_diff > context.config.struct_field_align_threshold() {
 225         field_prefix_max_width = 0;
 226     }
 227
 228     let items = itemize_list(
 229         context.snippet_provider,
 230         fields.iter(),
 231         "}",
 232         ",",
 233         |field| field.get_span().lo(),
 234         |field| field.get_span().hi(),
 235         |field| field.rewrite_aligned_item(context, item_shape, field_prefix_max_width),
 236         span.lo(),
 237         span.hi(),
 238         false,
 239     ).collect::<Vec<_>>();
 240
 241     let tactic = definitive_tactic(
 242         &items,
 243         ListTactic::HorizontalVertical,
 244         Separator::Comma,
 245         one_line_width,
 246     );
 247
 248     let fmt = ListFormatting::new(item_shape, context.config)
 249         .tactic(tactic)
 250         .trailing_separator(context.config.trailing_comma())
 251         .preserve_newline(true);
 252     write_list(&items, &fmt)
 253 }
 254
 255 fn group_aligned_items<T: AlignedItem>(
 256     context: &RewriteContext,
 257     fields: &[T],
 258 ) -> (&'static str, usize) {
 259     let mut index = 0;
 260     for i in 0..fields.len() - 1 {
 261         if fields[i].skip() {
 262             return ("", index);
 263         }
 264         // See if there are comments or empty lines between fields.
 265         let span = mk_sp(fields[i].get_span().hi(), fields[i + 1].get_span().lo());
 266         let snippet = context
 267             .snippet(span)
 268             .lines()
 269             .skip(1)
 270             .collect::<Vec<_>>()
 271             .join("\n");
 272         let spacings = if snippet.lines().rev().skip(1).any(|l| l.trim().is_empty()) {
 273             "\n"
 274         } else {
 275             ""
 276         };
 277         if contains_comment(&snippet) || snippet.lines().count() > 1 {
 278             return (spacings, index);
 279         }
 280         index += 1;
 281     }
 282     ("", index)
 283 }