src/attr.rs

   1 // Copyright 2018 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 attributes and meta items.
  12
  13 use syntax::ast;
  14 use syntax::source_map::{BytePos, Span, DUMMY_SP};
  15
  16 use crate::comment::{contains_comment, rewrite_doc_comment, CommentStyle};
  17 use crate::config::lists::*;
  18 use crate::config::IndentStyle;
  19 use crate::expr::rewrite_literal;
  20 use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  21 use crate::overflow;
  22 use crate::rewrite::{Rewrite, RewriteContext};
  23 use crate::shape::Shape;
  24 use crate::types::{rewrite_path, PathContext};
  25 use crate::utils::{count_newlines, mk_sp};
  26
  27 /// Returns attributes on the given statement.
  28 pub fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
  29     match stmt.node {
  30         ast::StmtKind::Local(ref local) => &local.attrs,
  31         ast::StmtKind::Item(ref item) => &item.attrs,
  32         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
  33         ast::StmtKind::Mac(ref mac) => &mac.2,
  34     }
  35 }
  36
  37 pub fn get_span_without_attrs(stmt: &ast::Stmt) -> Span {
  38     match stmt.node {
  39         ast::StmtKind::Local(ref local) => local.span,
  40         ast::StmtKind::Item(ref item) => item.span,
  41         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => expr.span,
  42         ast::StmtKind::Mac(ref mac) => {
  43             let (ref mac, _, _) = **mac;
  44             mac.span
  45         }
  46     }
  47 }
  48
  49 /// Returns attributes that are within `outer_span`.
  50 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
  51     attrs
  52         .iter()
  53         .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
  54         .cloned()
  55         .collect()
  56 }
  57
  58 fn is_derive(attr: &ast::Attribute) -> bool {
  59     attr.check_name("derive")
  60 }
  61
  62 /// Returns the arguments of `#[derive(...)]`.
  63 fn get_derive_spans(attr: &ast::Attribute) -> Option<Vec<Span>> {
  64     attr.meta_item_list().map(|meta_item_list| {
  65         meta_item_list
  66             .iter()
  67             .map(|nested_meta_item| nested_meta_item.span)
  68             .collect()
  69     })
  70 }
  71
  72 // The shape of the arguments to a function-like attribute.
  73 fn argument_shape(
  74     left: usize,
  75     right: usize,
  76     combine: bool,
  77     shape: Shape,
  78     context: &RewriteContext<'_>,
  79 ) -> Option<Shape> {
  80     match context.config.indent_style() {
  81         IndentStyle::Block => {
  82             if combine {
  83                 shape.offset_left(left)
  84             } else {
  85                 Some(
  86                     shape
  87                         .block_indent(context.config.tab_spaces())
  88                         .with_max_width(context.config),
  89                 )
  90             }
  91         }
  92         IndentStyle::Visual => shape
  93             .visual_indent(0)
  94             .shrink_left(left)
  95             .and_then(|s| s.sub_width(right)),
  96     }
  97 }
  98
  99 fn format_derive(
 100     derive_args: &[Span],
 101     prefix: &str,
 102     shape: Shape,
 103     context: &RewriteContext<'_>,
 104 ) -> Option<String> {
 105     let mut result = String::with_capacity(128);
 106     result.push_str(prefix);
 107     result.push_str("[derive(");
 108
 109     let argument_shape = argument_shape(10 + prefix.len(), 2, false, shape, context)?;
 110     let item_str = format_arg_list(
 111         derive_args.iter(),
 112         |_| DUMMY_SP.lo(),
 113         |_| DUMMY_SP.hi(),
 114         |sp| Some(context.snippet(**sp).to_owned()),
 115         DUMMY_SP,
 116         context,
 117         argument_shape,
 118         // 10 = "[derive()]", 3 = "()" and "]"
 119         shape.offset_left(10 + prefix.len())?.sub_width(3)?,
 120         None,
 121         false,
 122     )?;
 123
 124     result.push_str(&item_str);
 125     if item_str.starts_with('\n') {
 126         result.push(',');
 127         result.push_str(&shape.indent.to_string_with_newline(context.config));
 128     }
 129     result.push_str(")]");
 130     Some(result)
 131 }
 132
 133 /// Returns the first group of attributes that fills the given predicate.
 134 /// We consider two doc comments are in different group if they are separated by normal comments.
 135 fn take_while_with_pred<'a, P>(
 136     context: &RewriteContext<'_>,
 137     attrs: &'a [ast::Attribute],
 138     pred: P,
 139 ) -> &'a [ast::Attribute]
 140 where
 141     P: Fn(&ast::Attribute) -> bool,
 142 {
 143     let mut len = 0;
 144     let mut iter = attrs.iter().peekable();
 145
 146     while let Some(attr) = iter.next() {
 147         if pred(attr) {
 148             len += 1;
 149         } else {
 150             break;
 151         }
 152         if let Some(next_attr) = iter.peek() {
 153             // Extract comments between two attributes.
 154             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 155             let snippet = context.snippet(span_between_attr);
 156             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 157                 break;
 158             }
 159         }
 160     }
 161
 162     &attrs[..len]
 163 }
 164
 165 /// Rewrite the any doc comments which come before any other attributes.
 166 fn rewrite_initial_doc_comments(
 167     context: &RewriteContext<'_>,
 168     attrs: &[ast::Attribute],
 169     shape: Shape,
 170 ) -> Option<(usize, Option<String>)> {
 171     if attrs.is_empty() {
 172         return Some((0, None));
 173     }
 174     // Rewrite doc comments
 175     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 176     if !sugared_docs.is_empty() {
 177         let snippet = sugared_docs
 178             .iter()
 179             .map(|a| context.snippet(a.span))
 180             .collect::<Vec<_>>()
 181             .join("\n");
 182         return Some((
 183             sugared_docs.len(),
 184             Some(rewrite_doc_comment(
 185                 &snippet,
 186                 shape.comment(context.config),
 187                 context.config,
 188             )?),
 189         ));
 190     }
 191
 192     Some((0, None))
 193 }
 194
 195 impl Rewrite for ast::NestedMetaItem {
 196     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 197         match self.node {
 198             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 199             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 200         }
 201     }
 202 }
 203
 204 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 205     // Look at before and after comment and see if there are any empty lines.
 206     let comment_begin = comment.find('/');
 207     let len = comment_begin.unwrap_or_else(|| comment.len());
 208     let mlb = count_newlines(&comment[..len]) > 1;
 209     let mla = if comment_begin.is_none() {
 210         mlb
 211     } else {
 212         comment
 213             .chars()
 214             .rev()
 215             .take_while(|c| c.is_whitespace())
 216             .filter(|&c| c == '\n')
 217             .count()
 218             > 1
 219     };
 220     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 221 }
 222
 223 impl Rewrite for ast::MetaItem {
 224     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 225         Some(match self.node {
 226             ast::MetaItemKind::Word => {
 227                 rewrite_path(context, PathContext::Type, None, &self.ident, shape)?
 228             }
 229             ast::MetaItemKind::List(ref list) => {
 230                 let path = rewrite_path(context, PathContext::Type, None, &self.ident, shape)?;
 231                 let has_trailing_comma = crate::expr::span_ends_with_comma(context, self.span);
 232                 overflow::rewrite_with_parens(
 233                     context,
 234                     &path,
 235                     list.iter(),
 236                     // 1 = "]"
 237                     shape.sub_width(1)?,
 238                     self.span,
 239                     context.config.width_heuristics().attr_fn_like_width,
 240                     Some(if has_trailing_comma {
 241                         SeparatorTactic::Always
 242                     } else {
 243                         SeparatorTactic::Never
 244                     }),
 245                 )?
 246             }
 247             ast::MetaItemKind::NameValue(ref literal) => {
 248                 let path = rewrite_path(context, PathContext::Type, None, &self.ident, shape)?;
 249                 // 3 = ` = `
 250                 let lit_shape = shape.shrink_left(path.len() + 3)?;
 251                 // `rewrite_literal` returns `None` when `literal` exceeds max
 252                 // width. Since a literal is basically unformattable unless it
 253                 // is a string literal (and only if `format_strings` is set),
 254                 // we might be better off ignoring the fact that the attribute
 255                 // is longer than the max width and contiue on formatting.
 256                 // See #2479 for example.
 257                 let value = rewrite_literal(context, literal, lit_shape)
 258                     .unwrap_or_else(|| context.snippet(literal.span).to_owned());
 259                 format!("{} = {}", path, value)
 260             }
 261         })
 262     }
 263 }
 264
 265 fn format_arg_list<I, T, F1, F2, F3>(
 266     list: I,
 267     get_lo: F1,
 268     get_hi: F2,
 269     get_item_string: F3,
 270     span: Span,
 271     context: &RewriteContext<'_>,
 272     shape: Shape,
 273     one_line_shape: Shape,
 274     one_line_limit: Option<usize>,
 275     combine: bool,
 276 ) -> Option<String>
 277 where
 278     I: Iterator<Item = T>,
 279     F1: Fn(&T) -> BytePos,
 280     F2: Fn(&T) -> BytePos,
 281     F3: Fn(&T) -> Option<String>,
 282 {
 283     let items = itemize_list(
 284         context.snippet_provider,
 285         list,
 286         ")",
 287         ",",
 288         get_lo,
 289         get_hi,
 290         get_item_string,
 291         span.lo(),
 292         span.hi(),
 293         false,
 294     );
 295     let item_vec = items.collect::<Vec<_>>();
 296     let tactic = if let Some(limit) = one_line_limit {
 297         ListTactic::LimitedHorizontalVertical(limit)
 298     } else {
 299         ListTactic::HorizontalVertical
 300     };
 301
 302     let tactic = definitive_tactic(&item_vec, tactic, Separator::Comma, shape.width);
 303     let fmt = ListFormatting::new(shape, context.config)
 304         .tactic(tactic)
 305         .ends_with_newline(false);
 306     let item_str = write_list(&item_vec, &fmt)?;
 307
 308     let one_line_budget = one_line_shape.width;
 309     if context.config.indent_style() == IndentStyle::Visual
 310         || combine
 311         || (!item_str.contains('\n') && item_str.len() <= one_line_budget)
 312     {
 313         Some(item_str)
 314     } else {
 315         let nested_indent = shape.indent.to_string_with_newline(context.config);
 316         Some(format!("{}{}", nested_indent, item_str))
 317     }
 318 }
 319
 320 impl Rewrite for ast::Attribute {
 321     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 322         let snippet = context.snippet(self.span);
 323         if self.is_sugared_doc {
 324             rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
 325         } else {
 326             let prefix = attr_prefix(self);
 327
 328             if contains_comment(snippet) {
 329                 return Some(snippet.to_owned());
 330             }
 331
 332             if let Some(ref meta) = self.meta() {
 333                 // This attribute is possibly a doc attribute needing normalization to a doc comment
 334                 if context.config.normalize_doc_attributes() && meta.check_name("doc") {
 335                     if let Some(ref literal) = meta.value_str() {
 336                         let comment_style = match self.style {
 337                             ast::AttrStyle::Inner => CommentStyle::Doc,
 338                             ast::AttrStyle::Outer => CommentStyle::TripleSlash,
 339                         };
 340
 341                         // Remove possible whitespace from the `CommentStyle::opener()` so that
 342                         // the literal itself has control over the comment's leading spaces.
 343                         let opener = comment_style.opener().trim_end();
 344
 345                         let doc_comment = format!("{}{}", opener, literal);
 346                         return rewrite_doc_comment(
 347                             &doc_comment,
 348                             shape.comment(context.config),
 349                             context.config,
 350                         );
 351                     }
 352                 }
 353
 354                 // 1 = `[`
 355                 let shape = shape.offset_left(prefix.len() + 1)?;
 356                 Some(
 357                     meta.rewrite(context, shape)
 358                         .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
 359                 )
 360             } else {
 361                 Some(snippet.to_owned())
 362             }
 363         }
 364     }
 365 }
 366
 367 impl<'a> Rewrite for [ast::Attribute] {
 368     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 369         if self.is_empty() {
 370             return Some(String::new());
 371         }
 372
 373         // The current remaining attributes.
 374         let mut attrs = self;
 375         let mut result = String::new();
 376
 377         // This is not just a simple map because we need to handle doc comments
 378         // (where we take as many doc comment attributes as possible) and possibly
 379         // merging derives into a single attribute.
 380         loop {
 381             if attrs.is_empty() {
 382                 return Some(result);
 383             }
 384
 385             // Handle doc comments.
 386             let (doc_comment_len, doc_comment_str) =
 387                 rewrite_initial_doc_comments(context, attrs, shape)?;
 388             if doc_comment_len > 0 {
 389                 let doc_comment_str = doc_comment_str.expect("doc comments, but no result");
 390                 result.push_str(&doc_comment_str);
 391
 392                 let missing_span = attrs
 393                     .get(doc_comment_len)
 394                     .map(|next| mk_sp(attrs[doc_comment_len - 1].span.hi(), next.span.lo()));
 395                 if let Some(missing_span) = missing_span {
 396                     let snippet = context.snippet(missing_span);
 397                     let (mla, mlb) = has_newlines_before_after_comment(snippet);
 398                     let comment = crate::comment::recover_missing_comment_in_span(
 399                         missing_span,
 400                         shape.with_max_width(context.config),
 401                         context,
 402                         0,
 403                     )?;
 404                     let comment = if comment.is_empty() {
 405                         format!("\n{}", mlb)
 406                     } else {
 407                         format!("{}{}\n{}", mla, comment, mlb)
 408                     };
 409                     result.push_str(&comment);
 410                     result.push_str(&shape.indent.to_string(context.config));
 411                 }
 412
 413                 attrs = &attrs[doc_comment_len..];
 414
 415                 continue;
 416             }
 417
 418             // Handle derives if we will merge them.
 419             if context.config.merge_derives() && is_derive(&attrs[0]) {
 420                 let derives = take_while_with_pred(context, attrs, is_derive);
 421                 let mut derive_spans = vec![];
 422                 for derive in derives {
 423                     derive_spans.append(&mut get_derive_spans(derive)?);
 424                 }
 425                 let derive_str =
 426                     format_derive(&derive_spans, attr_prefix(&attrs[0]), shape, context)?;
 427                 result.push_str(&derive_str);
 428
 429                 let missing_span = attrs
 430                     .get(derives.len())
 431                     .map(|next| mk_sp(attrs[derives.len() - 1].span.hi(), next.span.lo()));
 432                 if let Some(missing_span) = missing_span {
 433                     let comment = crate::comment::recover_missing_comment_in_span(
 434                         missing_span,
 435                         shape.with_max_width(context.config),
 436                         context,
 437                         0,
 438                     )?;
 439                     result.push_str(&comment);
 440                     if let Some(next) = attrs.get(derives.len()) {
 441                         if next.is_sugared_doc {
 442                             let snippet = context.snippet(missing_span);
 443                             let (_, mlb) = has_newlines_before_after_comment(snippet);
 444                             result.push_str(&mlb);
 445                         }
 446                     }
 447                     result.push('\n');
 448                     result.push_str(&shape.indent.to_string(context.config));
 449                 }
 450
 451                 attrs = &attrs[derives.len()..];
 452
 453                 continue;
 454             }
 455
 456             // If we get here, then we have a regular attribute, just handle one
 457             // at a time.
 458
 459             let formatted_attr = attrs[0].rewrite(context, shape)?;
 460             result.push_str(&formatted_attr);
 461
 462             let missing_span = attrs
 463                 .get(1)
 464                 .map(|next| mk_sp(attrs[0].span.hi(), next.span.lo()));
 465             if let Some(missing_span) = missing_span {
 466                 let comment = crate::comment::recover_missing_comment_in_span(
 467                     missing_span,
 468                     shape.with_max_width(context.config),
 469                     context,
 470                     0,
 471                 )?;
 472                 result.push_str(&comment);
 473                 if let Some(next) = attrs.get(1) {
 474                     if next.is_sugared_doc {
 475                         let snippet = context.snippet(missing_span);
 476                         let (_, mlb) = has_newlines_before_after_comment(snippet);
 477                         result.push_str(&mlb);
 478                     }
 479                 }
 480                 result.push('\n');
 481                 result.push_str(&shape.indent.to_string(context.config));
 482             }
 483
 484             attrs = &attrs[1..];
 485         }
 486     }
 487 }
 488
 489 fn attr_prefix(attr: &ast::Attribute) -> &'static str {
 490     match attr.style {
 491         ast::AttrStyle::Inner => "#!",
 492         ast::AttrStyle::Outer => "#",
 493     }
 494 }