src/tools/rustfmt/src/attr.rs

   1 //! Format attributes and meta items.
   2
   3 use rustc_ast::ast;
   4 use rustc_ast::HasAttrs;
   5 use rustc_span::{symbol::sym, Span, Symbol};
   6
   7 use self::doc_comment::DocCommentFormatter;
   8 use crate::comment::{contains_comment, rewrite_doc_comment, CommentStyle};
   9 use crate::config::lists::*;
  10 use crate::config::IndentStyle;
  11 use crate::expr::rewrite_literal;
  12 use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
  13 use crate::overflow;
  14 use crate::rewrite::{Rewrite, RewriteContext};
  15 use crate::shape::Shape;
  16 use crate::source_map::SpanUtils;
  17 use crate::types::{rewrite_path, PathContext};
  18 use crate::utils::{count_newlines, mk_sp};
  19
  20 mod doc_comment;
  21
  22 pub(crate) fn contains_name(attrs: &[ast::Attribute], name: Symbol) -> bool {
  23     attrs.iter().any(|attr| attr.has_name(name))
  24 }
  25
  26 pub(crate) fn first_attr_value_str_by_name(
  27     attrs: &[ast::Attribute],
  28     name: Symbol,
  29 ) -> Option<Symbol> {
  30     attrs
  31         .iter()
  32         .find(|attr| attr.has_name(name))
  33         .and_then(|attr| attr.value_str())
  34 }
  35
  36 /// Returns attributes on the given statement.
  37 pub(crate) fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
  38     stmt.attrs()
  39 }
  40
  41 pub(crate) fn get_span_without_attrs(stmt: &ast::Stmt) -> Span {
  42     match stmt.kind {
  43         ast::StmtKind::Local(ref local) => local.span,
  44         ast::StmtKind::Item(ref item) => item.span,
  45         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => expr.span,
  46         ast::StmtKind::MacCall(ref mac_stmt) => mac_stmt.mac.span(),
  47         ast::StmtKind::Empty => stmt.span,
  48     }
  49 }
  50
  51 /// Returns attributes that are within `outer_span`.
  52 pub(crate) fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> ast::AttrVec {
  53     attrs
  54         .iter()
  55         .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
  56         .cloned()
  57         .collect()
  58 }
  59
  60 fn is_derive(attr: &ast::Attribute) -> bool {
  61     attr.has_name(sym::derive)
  62 }
  63
  64 // The shape of the arguments to a function-like attribute.
  65 fn argument_shape(
  66     left: usize,
  67     right: usize,
  68     combine: bool,
  69     shape: Shape,
  70     context: &RewriteContext<'_>,
  71 ) -> Option<Shape> {
  72     match context.config.indent_style() {
  73         IndentStyle::Block => {
  74             if combine {
  75                 shape.offset_left(left)
  76             } else {
  77                 Some(
  78                     shape
  79                         .block_indent(context.config.tab_spaces())
  80                         .with_max_width(context.config),
  81                 )
  82             }
  83         }
  84         IndentStyle::Visual => shape
  85             .visual_indent(0)
  86             .shrink_left(left)
  87             .and_then(|s| s.sub_width(right)),
  88     }
  89 }
  90
  91 fn format_derive(
  92     derives: &[ast::Attribute],
  93     shape: Shape,
  94     context: &RewriteContext<'_>,
  95 ) -> Option<String> {
  96     // Collect all items from all attributes
  97     let all_items = derives
  98         .iter()
  99         .map(|attr| {
 100             // Parse the derive items and extract the span for each item; if any
 101             // attribute is not parseable, none of the attributes will be
 102             // reformatted.
 103             let item_spans = attr.meta_item_list().map(|meta_item_list| {
 104                 meta_item_list
 105                     .into_iter()
 106                     .map(|nested_meta_item| nested_meta_item.span())
 107             })?;
 108
 109             let items = itemize_list(
 110                 context.snippet_provider,
 111                 item_spans,
 112                 ")",
 113                 ",",
 114                 |span| span.lo(),
 115                 |span| span.hi(),
 116                 |span| Some(context.snippet(*span).to_owned()),
 117                 // We update derive attribute spans to start after the opening '('
 118                 // This helps us focus parsing to just what's inside #[derive(...)]
 119                 context.snippet_provider.span_after(attr.span, "("),
 120                 attr.span.hi(),
 121                 false,
 122             );
 123
 124             Some(items)
 125         })
 126         // Fail if any attribute failed.
 127         .collect::<Option<Vec<_>>>()?
 128         // Collect the results into a single, flat, Vec.
 129         .into_iter()
 130         .flatten()
 131         .collect::<Vec<_>>();
 132
 133     // Collect formatting parameters.
 134     let prefix = attr_prefix(&derives[0]);
 135     let argument_shape = argument_shape(
 136         "[derive()]".len() + prefix.len(),
 137         ")]".len(),
 138         false,
 139         shape,
 140         context,
 141     )?;
 142     let one_line_shape = shape
 143         .offset_left("[derive()]".len() + prefix.len())?
 144         .sub_width("()]".len())?;
 145     let one_line_budget = one_line_shape.width;
 146
 147     let tactic = definitive_tactic(
 148         &all_items,
 149         ListTactic::HorizontalVertical,
 150         Separator::Comma,
 151         argument_shape.width,
 152     );
 153     let trailing_separator = match context.config.indent_style() {
 154         // We always add the trailing comma and remove it if it is not needed.
 155         IndentStyle::Block => SeparatorTactic::Always,
 156         IndentStyle::Visual => SeparatorTactic::Never,
 157     };
 158
 159     // Format the collection of items.
 160     let fmt = ListFormatting::new(argument_shape, context.config)
 161         .tactic(tactic)
 162         .trailing_separator(trailing_separator)
 163         .ends_with_newline(false);
 164     let item_str = write_list(&all_items, &fmt)?;
 165
 166     debug!("item_str: '{}'", item_str);
 167
 168     // Determine if the result will be nested, i.e. if we're using the block
 169     // indent style and either the items are on multiple lines or we've exceeded
 170     // our budget to fit on a single line.
 171     let nested = context.config.indent_style() == IndentStyle::Block
 172         && (item_str.contains('\n') || item_str.len() > one_line_budget);
 173
 174     // Format the final result.
 175     let mut result = String::with_capacity(128);
 176     result.push_str(prefix);
 177     result.push_str("[derive(");
 178     if nested {
 179         let nested_indent = argument_shape.indent.to_string_with_newline(context.config);
 180         result.push_str(&nested_indent);
 181         result.push_str(&item_str);
 182         result.push_str(&shape.indent.to_string_with_newline(context.config));
 183     } else if let SeparatorTactic::Always = context.config.trailing_comma() {
 184         // Retain the trailing comma.
 185         result.push_str(&item_str);
 186     } else if item_str.ends_with(',') {
 187         // Remove the trailing comma.
 188         result.push_str(&item_str[..item_str.len() - 1]);
 189     } else {
 190         result.push_str(&item_str);
 191     }
 192     result.push_str(")]");
 193
 194     Some(result)
 195 }
 196
 197 /// Returns the first group of attributes that fills the given predicate.
 198 /// We consider two doc comments are in different group if they are separated by normal comments.
 199 fn take_while_with_pred<'a, P>(
 200     context: &RewriteContext<'_>,
 201     attrs: &'a [ast::Attribute],
 202     pred: P,
 203 ) -> &'a [ast::Attribute]
 204 where
 205     P: Fn(&ast::Attribute) -> bool,
 206 {
 207     let mut len = 0;
 208     let mut iter = attrs.iter().peekable();
 209
 210     while let Some(attr) = iter.next() {
 211         if pred(attr) {
 212             len += 1;
 213         } else {
 214             break;
 215         }
 216         if let Some(next_attr) = iter.peek() {
 217             // Extract comments between two attributes.
 218             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 219             let snippet = context.snippet(span_between_attr);
 220             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 221                 break;
 222             }
 223         }
 224     }
 225
 226     &attrs[..len]
 227 }
 228
 229 /// Rewrite the any doc comments which come before any other attributes.
 230 fn rewrite_initial_doc_comments(
 231     context: &RewriteContext<'_>,
 232     attrs: &[ast::Attribute],
 233     shape: Shape,
 234 ) -> Option<(usize, Option<String>)> {
 235     if attrs.is_empty() {
 236         return Some((0, None));
 237     }
 238     // Rewrite doc comments
 239     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_doc_comment());
 240     if !sugared_docs.is_empty() {
 241         let snippet = sugared_docs
 242             .iter()
 243             .map(|a| context.snippet(a.span))
 244             .collect::<Vec<_>>()
 245             .join("\n");
 246         return Some((
 247             sugared_docs.len(),
 248             Some(rewrite_doc_comment(
 249                 &snippet,
 250                 shape.comment(context.config),
 251                 context.config,
 252             )?),
 253         ));
 254     }
 255
 256     Some((0, None))
 257 }
 258
 259 impl Rewrite for ast::NestedMetaItem {
 260     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 261         match self {
 262             ast::NestedMetaItem::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 263             ast::NestedMetaItem::Lit(ref l) => {
 264                 rewrite_literal(context, l.as_token_lit(), l.span, shape)
 265             }
 266         }
 267     }
 268 }
 269
 270 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 271     // Look at before and after comment and see if there are any empty lines.
 272     let comment_begin = comment.find('/');
 273     let len = comment_begin.unwrap_or_else(|| comment.len());
 274     let mlb = count_newlines(&comment[..len]) > 1;
 275     let mla = if comment_begin.is_none() {
 276         mlb
 277     } else {
 278         comment
 279             .chars()
 280             .rev()
 281             .take_while(|c| c.is_whitespace())
 282             .filter(|&c| c == '\n')
 283             .count()
 284             > 1
 285     };
 286     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 287 }
 288
 289 impl Rewrite for ast::MetaItem {
 290     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 291         Some(match self.kind {
 292             ast::MetaItemKind::Word => {
 293                 rewrite_path(context, PathContext::Type, &None, &self.path, shape)?
 294             }
 295             ast::MetaItemKind::List(ref list) => {
 296                 let path = rewrite_path(context, PathContext::Type, &None, &self.path, shape)?;
 297                 let has_trailing_comma = crate::expr::span_ends_with_comma(context, self.span);
 298                 overflow::rewrite_with_parens(
 299                     context,
 300                     &path,
 301                     list.iter(),
 302                     // 1 = "]"
 303                     shape.sub_width(1)?,
 304                     self.span,
 305                     context.config.attr_fn_like_width(),
 306                     Some(if has_trailing_comma {
 307                         SeparatorTactic::Always
 308                     } else {
 309                         SeparatorTactic::Never
 310                     }),
 311                 )?
 312             }
 313             ast::MetaItemKind::NameValue(ref lit) => {
 314                 let path = rewrite_path(context, PathContext::Type, &None, &self.path, shape)?;
 315                 // 3 = ` = `
 316                 let lit_shape = shape.shrink_left(path.len() + 3)?;
 317                 // `rewrite_literal` returns `None` when `lit` exceeds max
 318                 // width. Since a literal is basically unformattable unless it
 319                 // is a string literal (and only if `format_strings` is set),
 320                 // we might be better off ignoring the fact that the attribute
 321                 // is longer than the max width and continue on formatting.
 322                 // See #2479 for example.
 323                 let value = rewrite_literal(context, lit.as_token_lit(), lit.span, lit_shape)
 324                     .unwrap_or_else(|| context.snippet(lit.span).to_owned());
 325                 format!("{} = {}", path, value)
 326             }
 327         })
 328     }
 329 }
 330
 331 impl Rewrite for ast::Attribute {
 332     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 333         let snippet = context.snippet(self.span);
 334         if self.is_doc_comment() {
 335             rewrite_doc_comment(snippet, shape.comment(context.config), context.config)
 336         } else {
 337             let should_skip = self
 338                 .ident()
 339                 .map(|s| context.skip_context.attributes.skip(s.name.as_str()))
 340                 .unwrap_or(false);
 341             let prefix = attr_prefix(self);
 342
 343             if should_skip || contains_comment(snippet) {
 344                 return Some(snippet.to_owned());
 345             }
 346
 347             if let Some(ref meta) = self.meta() {
 348                 // This attribute is possibly a doc attribute needing normalization to a doc comment
 349                 if context.config.normalize_doc_attributes() && meta.has_name(sym::doc) {
 350                     if let Some(ref literal) = meta.value_str() {
 351                         let comment_style = match self.style {
 352                             ast::AttrStyle::Inner => CommentStyle::Doc,
 353                             ast::AttrStyle::Outer => CommentStyle::TripleSlash,
 354                         };
 355
 356                         let literal_str = literal.as_str();
 357                         let doc_comment_formatter =
 358                             DocCommentFormatter::new(literal_str, comment_style);
 359                         let doc_comment = format!("{}", doc_comment_formatter);
 360                         return rewrite_doc_comment(
 361                             &doc_comment,
 362                             shape.comment(context.config),
 363                             context.config,
 364                         );
 365                     }
 366                 }
 367
 368                 // 1 = `[`
 369                 let shape = shape.offset_left(prefix.len() + 1)?;
 370                 Some(
 371                     meta.rewrite(context, shape)
 372                         .map_or_else(|| snippet.to_owned(), |rw| format!("{}[{}]", prefix, rw)),
 373                 )
 374             } else {
 375                 Some(snippet.to_owned())
 376             }
 377         }
 378     }
 379 }
 380
 381 impl Rewrite for [ast::Attribute] {
 382     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
 383         if self.is_empty() {
 384             return Some(String::new());
 385         }
 386
 387         // The current remaining attributes.
 388         let mut attrs = self;
 389         let mut result = String::new();
 390
 391         // Determine if the source text is annotated with `#[rustfmt::skip::attributes(derive)]`
 392         // or `#![rustfmt::skip::attributes(derive)]`
 393         let skip_derives = context.skip_context.attributes.skip("derive");
 394
 395         // This is not just a simple map because we need to handle doc comments
 396         // (where we take as many doc comment attributes as possible) and possibly
 397         // merging derives into a single attribute.
 398         loop {
 399             if attrs.is_empty() {
 400                 return Some(result);
 401             }
 402
 403             // Handle doc comments.
 404             let (doc_comment_len, doc_comment_str) =
 405                 rewrite_initial_doc_comments(context, attrs, shape)?;
 406             if doc_comment_len > 0 {
 407                 let doc_comment_str = doc_comment_str.expect("doc comments, but no result");
 408                 result.push_str(&doc_comment_str);
 409
 410                 let missing_span = attrs
 411                     .get(doc_comment_len)
 412                     .map(|next| mk_sp(attrs[doc_comment_len - 1].span.hi(), next.span.lo()));
 413                 if let Some(missing_span) = missing_span {
 414                     let snippet = context.snippet(missing_span);
 415                     let (mla, mlb) = has_newlines_before_after_comment(snippet);
 416                     let comment = crate::comment::recover_missing_comment_in_span(
 417                         missing_span,
 418                         shape.with_max_width(context.config),
 419                         context,
 420                         0,
 421                     )?;
 422                     let comment = if comment.is_empty() {
 423                         format!("\n{}", mlb)
 424                     } else {
 425                         format!("{}{}\n{}", mla, comment, mlb)
 426                     };
 427                     result.push_str(&comment);
 428                     result.push_str(&shape.indent.to_string(context.config));
 429                 }
 430
 431                 attrs = &attrs[doc_comment_len..];
 432
 433                 continue;
 434             }
 435
 436             // Handle derives if we will merge them.
 437             if !skip_derives && context.config.merge_derives() && is_derive(&attrs[0]) {
 438                 let derives = take_while_with_pred(context, attrs, is_derive);
 439                 let derive_str = format_derive(derives, shape, context)?;
 440                 result.push_str(&derive_str);
 441
 442                 let missing_span = attrs
 443                     .get(derives.len())
 444                     .map(|next| mk_sp(attrs[derives.len() - 1].span.hi(), next.span.lo()));
 445                 if let Some(missing_span) = missing_span {
 446                     let comment = crate::comment::recover_missing_comment_in_span(
 447                         missing_span,
 448                         shape.with_max_width(context.config),
 449                         context,
 450                         0,
 451                     )?;
 452                     result.push_str(&comment);
 453                     if let Some(next) = attrs.get(derives.len()) {
 454                         if next.is_doc_comment() {
 455                             let snippet = context.snippet(missing_span);
 456                             let (_, mlb) = has_newlines_before_after_comment(snippet);
 457                             result.push_str(mlb);
 458                         }
 459                     }
 460                     result.push('\n');
 461                     result.push_str(&shape.indent.to_string(context.config));
 462                 }
 463
 464                 attrs = &attrs[derives.len()..];
 465
 466                 continue;
 467             }
 468
 469             // If we get here, then we have a regular attribute, just handle one
 470             // at a time.
 471
 472             let formatted_attr = attrs[0].rewrite(context, shape)?;
 473             result.push_str(&formatted_attr);
 474
 475             let missing_span = attrs
 476                 .get(1)
 477                 .map(|next| mk_sp(attrs[0].span.hi(), next.span.lo()));
 478             if let Some(missing_span) = missing_span {
 479                 let comment = crate::comment::recover_missing_comment_in_span(
 480                     missing_span,
 481                     shape.with_max_width(context.config),
 482                     context,
 483                     0,
 484                 )?;
 485                 result.push_str(&comment);
 486                 if let Some(next) = attrs.get(1) {
 487                     if next.is_doc_comment() {
 488                         let snippet = context.snippet(missing_span);
 489                         let (_, mlb) = has_newlines_before_after_comment(snippet);
 490                         result.push_str(mlb);
 491                     }
 492                 }
 493                 result.push('\n');
 494                 result.push_str(&shape.indent.to_string(context.config));
 495             }
 496
 497             attrs = &attrs[1..];
 498         }
 499     }
 500 }
 501
 502 fn attr_prefix(attr: &ast::Attribute) -> &'static str {
 503     match attr.style {
 504         ast::AttrStyle::Inner => "#!",
 505         ast::AttrStyle::Outer => "#",
 506     }
 507 }
 508
 509 pub(crate) trait MetaVisitor<'ast> {
 510     fn visit_meta_item(&mut self, meta_item: &'ast ast::MetaItem) {
 511         match meta_item.kind {
 512             ast::MetaItemKind::Word => self.visit_meta_word(meta_item),
 513             ast::MetaItemKind::List(ref list) => self.visit_meta_list(meta_item, list),
 514             ast::MetaItemKind::NameValue(ref lit) => self.visit_meta_name_value(meta_item, lit),
 515         }
 516     }
 517
 518     fn visit_meta_list(
 519         &mut self,
 520         _meta_item: &'ast ast::MetaItem,
 521         list: &'ast [ast::NestedMetaItem],
 522     ) {
 523         for nm in list {
 524             self.visit_nested_meta_item(nm);
 525         }
 526     }
 527
 528     fn visit_meta_word(&mut self, _meta_item: &'ast ast::MetaItem) {}
 529
 530     fn visit_meta_name_value(
 531         &mut self,
 532         _meta_item: &'ast ast::MetaItem,
 533         _lit: &'ast ast::MetaItemLit,
 534     ) {
 535     }
 536
 537     fn visit_nested_meta_item(&mut self, nm: &'ast ast::NestedMetaItem) {
 538         match nm {
 539             ast::NestedMetaItem::MetaItem(ref meta_item) => self.visit_meta_item(meta_item),
 540             ast::NestedMetaItem::Lit(ref lit) => self.visit_meta_item_lit(lit),
 541         }
 542     }
 543
 544     fn visit_meta_item_lit(&mut self, _lit: &'ast ast::MetaItemLit) {}
 545 }