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 syntax::ast;
  16 use syntax::codemap::{BytePos, Span};
  17
  18 use {Indent, Shape, Spanned};
  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, ListTactic, Separator,
  24             SeparatorPlace};
  25 use rewrite::{Rewrite, RewriteContext};
  26 use utils::{contains_skip, is_attributes_extendable, mk_sp};
  27
  28 pub trait AlignedItem {
  29     fn skip(&self) -> bool;
  30     fn get_span(&self) -> Span;
  31     fn rewrite_prefix(&self, context: &RewriteContext, shape: Shape) -> Option<String>;
  32     fn rewrite_aligned_item(
  33         &self,
  34         context: &RewriteContext,
  35         shape: Shape,
  36         prefix_max_width: usize,
  37     ) -> Option<String>;
  38 }
  39
  40 impl AlignedItem for ast::StructField {
  41     fn skip(&self) -> bool {
  42         contains_skip(&self.attrs)
  43     }
  44
  45     fn get_span(&self) -> Span {
  46         self.span()
  47     }
  48
  49     fn rewrite_prefix(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
  50         let attrs_str = try_opt!(self.attrs.rewrite(context, shape));
  51         let missing_span = if self.attrs.is_empty() {
  52             mk_sp(self.span.lo(), self.span.lo())
  53         } else {
  54             mk_sp(self.attrs.last().unwrap().span.hi(), self.span.lo())
  55         };
  56         let attrs_extendable = context.config.attributes_on_same_line_as_field()
  57             && 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 = try_opt!(self.attrs.rewrite(context, shape));
  91         let name = &self.ident.node.to_string();
  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.codemap.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 = try_opt!(rewrite_aligned_items_inner(
 169         context,
 170         init,
 171         init_span,
 172         shape.indent,
 173         one_line_width,
 174     ));
 175     if rest.is_empty() {
 176         Some(result + spaces)
 177     } else {
 178         let rest_span = mk_sp(init_last_pos, span.hi());
 179         let rest_str = try_opt!(rewrite_with_alignment(
 180             rest,
 181             context,
 182             shape,
 183             rest_span,
 184             one_line_width,
 185         ));
 186         Some(
 187             result + spaces + "\n"
 188                 + &shape
 189                     .indent
 190                     .block_indent(context.config)
 191                     .to_string(context.config) + &rest_str,
 192         )
 193     }
 194 }
 195
 196 fn struct_field_preix_max_min_width<T: AlignedItem>(
 197     context: &RewriteContext,
 198     fields: &[T],
 199     shape: Shape,
 200 ) -> (usize, usize) {
 201     fields
 202         .iter()
 203         .map(|field| {
 204             field
 205                 .rewrite_prefix(context, shape)
 206                 .and_then(|field_str| if field_str.contains('\n') {
 207                     None
 208                 } else {
 209                     Some(field_str.len())
 210                 })
 211         })
 212         .fold(Some((0, ::std::usize::MAX)), |acc, len| match (acc, len) {
 213             (Some((max_len, min_len)), Some(len)) => {
 214                 Some((cmp::max(max_len, len), cmp::min(min_len, len)))
 215             }
 216             _ => None,
 217         })
 218         .unwrap_or((0, 0))
 219 }
 220
 221 fn rewrite_aligned_items_inner<T: AlignedItem>(
 222     context: &RewriteContext,
 223     fields: &[T],
 224     span: Span,
 225     offset: Indent,
 226     one_line_width: usize,
 227 ) -> Option<String> {
 228     let item_indent = offset.block_indent(context.config);
 229     // 1 = ","
 230     let item_shape = try_opt!(Shape::indented(item_indent, context.config).sub_width(1));
 231     let (mut field_prefix_max_width, field_prefix_min_width) =
 232         struct_field_preix_max_min_width(context, fields, item_shape);
 233     let max_diff = field_prefix_max_width
 234         .checked_sub(field_prefix_min_width)
 235         .unwrap_or(0);
 236     if max_diff > context.config.struct_field_align_threshold() {
 237         field_prefix_max_width = 0;
 238     }
 239
 240     let items = itemize_list(
 241         context.codemap,
 242         fields.iter(),
 243         "}",
 244         |field| field.get_span().lo(),
 245         |field| field.get_span().hi(),
 246         |field| field.rewrite_aligned_item(context, item_shape, field_prefix_max_width),
 247         span.lo(),
 248         span.hi(),
 249         false,
 250     ).collect::<Vec<_>>();
 251
 252     let tactic = definitive_tactic(
 253         &items,
 254         ListTactic::HorizontalVertical,
 255         Separator::Comma,
 256         one_line_width,
 257     );
 258
 259     let fmt = ListFormatting {
 260         tactic: tactic,
 261         separator: ",",
 262         trailing_separator: context.config.trailing_comma(),
 263         separator_place: SeparatorPlace::Back,
 264         shape: item_shape,
 265         ends_with_newline: true,
 266         preserve_newline: true,
 267         config: context.config,
 268     };
 269     write_list(&items, &fmt)
 270 }
 271
 272 fn group_aligned_items<T: AlignedItem>(
 273     context: &RewriteContext,
 274     fields: &[T],
 275 ) -> (&'static str, usize) {
 276     let mut index = 0;
 277     for i in 0..fields.len() - 1 {
 278         if fields[i].skip() {
 279             return ("", index);
 280         }
 281         // See if there are comments or empty lines between fields.
 282         let span = mk_sp(fields[i].get_span().hi(), fields[i + 1].get_span().lo());
 283         let snippet = context
 284             .snippet(span)
 285             .lines()
 286             .skip(1)
 287             .collect::<Vec<_>>()
 288             .join("\n");
 289         let spacings = if snippet.lines().rev().skip(1).any(|l| l.trim().is_empty()) {
 290             "\n"
 291         } else {
 292             ""
 293         };
 294         if contains_comment(&snippet) || snippet.lines().count() > 1 {
 295             return (spacings, index);
 296         }
 297         index += 1;
 298     }
 299     ("", index)
 300 }