src/visitor.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 std::cmp;
  12
  13 use syntax::{ast, visit};
  14 use syntax::attr::{self, HasAttrs};
  15 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  16 use syntax::parse::ParseSess;
  17
  18 use codemap::{LineRangeUtils, SpanUtils};
  19 use comment::{combine_strs_with_missing_comments, contains_comment, CodeCharKind,
  20               CommentCodeSlices, FindUncommented};
  21 use comment::rewrite_comment;
  22 use config::{BraceStyle, Config};
  23 use expr::rewrite_literal;
  24 use items::{format_impl, format_trait, format_trait_alias, rewrite_associated_impl_type,
  25             rewrite_associated_type, rewrite_type_alias, FnSig, StaticParts, StructParts};
  26 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  27             SeparatorTactic};
  28 use macros::{rewrite_macro, rewrite_macro_def, MacroPosition};
  29 use regex::Regex;
  30 use rewrite::{Rewrite, RewriteContext};
  31 use shape::{Indent, Shape};
  32 use spanned::Spanned;
  33 use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  34
  35 /// Returns attributes that are within `outer_span`.
  36 pub fn filter_inline_attrs(attrs: &[ast::Attribute], outer_span: Span) -> Vec<ast::Attribute> {
  37     attrs
  38         .iter()
  39         .filter(|a| outer_span.lo() <= a.span.lo() && a.span.hi() <= outer_span.hi())
  40         .cloned()
  41         .collect()
  42 }
  43
  44 /// Returns true for `mod foo;`, false for `mod foo { .. }`.
  45 fn is_mod_decl(item: &ast::Item) -> bool {
  46     match item.node {
  47         ast::ItemKind::Mod(ref m) => m.inner.hi() != item.span.hi(),
  48         _ => false,
  49     }
  50 }
  51
  52 fn contains_macro_use_attr(attrs: &[ast::Attribute], span: Span) -> bool {
  53     attr::contains_name(&filter_inline_attrs(attrs, span), "macro_use")
  54 }
  55
  56 /// Returns true for `mod foo;` without any inline attributes.
  57 /// We cannot reorder modules with attributes because doing so can break the code.
  58 /// e.g. `#[macro_use]`.
  59 fn is_mod_decl_without_attr(item: &ast::Item) -> bool {
  60     is_mod_decl(item) && !contains_macro_use_attr(&item.attrs, item.span())
  61 }
  62
  63 fn is_use_item(item: &ast::Item) -> bool {
  64     match item.node {
  65         ast::ItemKind::Use(_) => true,
  66         _ => false,
  67     }
  68 }
  69
  70 fn is_use_item_without_attr(item: &ast::Item) -> bool {
  71     is_use_item(item) && !contains_macro_use_attr(&item.attrs, item.span())
  72 }
  73
  74 fn is_extern_crate(item: &ast::Item) -> bool {
  75     match item.node {
  76         ast::ItemKind::ExternCrate(..) => true,
  77         _ => false,
  78     }
  79 }
  80
  81 fn is_extern_crate_without_attr(item: &ast::Item) -> bool {
  82     is_extern_crate(item) && !contains_macro_use_attr(&item.attrs, item.span())
  83 }
  84
  85 /// Creates a string slice corresponding to the specified span.
  86 pub struct SnippetProvider<'a> {
  87     /// A pointer to the content of the file we are formatting.
  88     big_snippet: &'a str,
  89     /// A position of the start of `big_snippet`, used as an offset.
  90     start_pos: usize,
  91 }
  92
  93 impl<'a> SnippetProvider<'a> {
  94     pub fn span_to_snippet(&self, span: Span) -> Option<&str> {
  95         let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
  96         let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
  97         Some(&self.big_snippet[start_index..end_index])
  98     }
  99
 100     pub fn new(start_pos: BytePos, big_snippet: &'a str) -> Self {
 101         let start_pos = start_pos.to_usize();
 102         SnippetProvider {
 103             big_snippet,
 104             start_pos,
 105         }
 106     }
 107 }
 108
 109 pub struct FmtVisitor<'a> {
 110     pub parse_session: &'a ParseSess,
 111     pub codemap: &'a CodeMap,
 112     pub buffer: String,
 113     pub last_pos: BytePos,
 114     // FIXME: use an RAII util or closure for indenting
 115     pub block_indent: Indent,
 116     pub config: &'a Config,
 117     pub is_if_else_block: bool,
 118     pub snippet_provider: &'a SnippetProvider<'a>,
 119     pub line_number: usize,
 120     pub skipped_range: Vec<(usize, usize)>,
 121 }
 122
 123 impl<'b, 'a: 'b> FmtVisitor<'a> {
 124     pub fn shape(&self) -> Shape {
 125         Shape::indented(self.block_indent, self.config)
 126     }
 127
 128     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
 129         debug!(
 130             "visit_stmt: {:?} {:?}",
 131             self.codemap.lookup_char_pos(stmt.span.lo()),
 132             self.codemap.lookup_char_pos(stmt.span.hi())
 133         );
 134
 135         match stmt.node {
 136             ast::StmtKind::Item(ref item) => {
 137                 self.visit_item(item);
 138             }
 139             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 140                 if contains_skip(get_attrs_from_stmt(stmt)) {
 141                     self.push_skipped_with_span(stmt.span());
 142                 } else {
 143                     let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 144                     self.push_rewrite(stmt.span(), rewrite)
 145                 }
 146             }
 147             ast::StmtKind::Mac(ref mac) => {
 148                 let (ref mac, _macro_style, ref attrs) = **mac;
 149                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 150                     self.push_skipped_with_span(stmt.span());
 151                 } else {
 152                     self.visit_mac(mac, None, MacroPosition::Statement);
 153                 }
 154                 self.format_missing(stmt.span.hi());
 155             }
 156         }
 157     }
 158
 159     pub fn visit_block(
 160         &mut self,
 161         b: &ast::Block,
 162         inner_attrs: Option<&[ast::Attribute]>,
 163         has_braces: bool,
 164     ) {
 165         debug!(
 166             "visit_block: {:?} {:?}",
 167             self.codemap.lookup_char_pos(b.span.lo()),
 168             self.codemap.lookup_char_pos(b.span.hi())
 169         );
 170
 171         // Check if this block has braces.
 172         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 173
 174         self.last_pos = self.last_pos + brace_compensation;
 175         self.block_indent = self.block_indent.block_indent(self.config);
 176         self.push_str("{");
 177
 178         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 179             if let Some(first_stmt) = b.stmts.first() {
 180                 let attr_lo = inner_attrs
 181                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 182                     .or_else(|| {
 183                         // Attributes for an item in a statement position
 184                         // do not belong to the statement. (rust-lang/rust#34459)
 185                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 186                             item.attrs.first()
 187                         } else {
 188                             first_stmt.attrs().first()
 189                         }.and_then(|attr| {
 190                             // Some stmts can have embedded attributes.
 191                             // e.g. `match { #![attr] ... }`
 192                             let attr_lo = attr.span.lo();
 193                             if attr_lo < first_stmt.span.lo() {
 194                                 Some(attr_lo)
 195                             } else {
 196                                 None
 197                             }
 198                         })
 199                     });
 200
 201                 let snippet = self.snippet(mk_sp(
 202                     self.last_pos,
 203                     attr_lo.unwrap_or(first_stmt.span.lo()),
 204                 ));
 205                 let len = CommentCodeSlices::new(snippet)
 206                     .nth(0)
 207                     .and_then(|(kind, _, s)| {
 208                         if kind == CodeCharKind::Normal {
 209                             s.rfind('\n')
 210                         } else {
 211                             None
 212                         }
 213                     });
 214                 if let Some(len) = len {
 215                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 216                 }
 217             }
 218         }
 219
 220         // Format inner attributes if available.
 221         let skip_rewrite = if let Some(attrs) = inner_attrs {
 222             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 223         } else {
 224             false
 225         };
 226
 227         if skip_rewrite {
 228             self.push_rewrite(b.span, None);
 229             self.close_block(false);
 230             self.last_pos = source!(self, b.span).hi();
 231             return;
 232         }
 233
 234         self.walk_block_stmts(b);
 235
 236         if !b.stmts.is_empty() {
 237             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 238                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 239                     self.push_str(";");
 240                 }
 241             }
 242         }
 243
 244         let mut remove_len = BytePos(0);
 245         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 246             if let Some(stmt) = b.stmts.last() {
 247                 let snippet = self.snippet(mk_sp(
 248                     stmt.span.hi(),
 249                     source!(self, b.span).hi() - brace_compensation,
 250                 ));
 251                 let len = CommentCodeSlices::new(snippet)
 252                     .last()
 253                     .and_then(|(kind, _, s)| {
 254                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 255                             Some(s.len())
 256                         } else {
 257                             None
 258                         }
 259                     });
 260                 if let Some(len) = len {
 261                     remove_len = BytePos::from_usize(len);
 262                 }
 263             }
 264         }
 265
 266         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 267             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 268             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 269             snippet.contains("//") || snippet.contains("/*")
 270         };
 271         // FIXME: we should compress any newlines here to just one
 272         if unindent_comment {
 273             self.block_indent = self.block_indent.block_unindent(self.config);
 274         }
 275         self.format_missing_with_indent(
 276             source!(self, b.span).hi() - brace_compensation - remove_len,
 277         );
 278         if unindent_comment {
 279             self.block_indent = self.block_indent.block_indent(self.config);
 280         }
 281         self.close_block(unindent_comment);
 282         self.last_pos = source!(self, b.span).hi();
 283     }
 284
 285     // FIXME: this is a terrible hack to indent the comments between the last
 286     // item in the block and the closing brace to the block's level.
 287     // The closing brace itself, however, should be indented at a shallower
 288     // level.
 289     fn close_block(&mut self, unindent_comment: bool) {
 290         let total_len = self.buffer.len();
 291         let chars_too_many = if unindent_comment {
 292             0
 293         } else if self.config.hard_tabs() {
 294             1
 295         } else {
 296             self.config.tab_spaces()
 297         };
 298         self.buffer.truncate(total_len - chars_too_many);
 299         self.push_str("}");
 300         self.block_indent = self.block_indent.block_unindent(self.config);
 301     }
 302
 303     // Note that this only gets called for function definitions. Required methods
 304     // on traits do not get handled here.
 305     fn visit_fn(
 306         &mut self,
 307         fk: visit::FnKind,
 308         generics: &ast::Generics,
 309         fd: &ast::FnDecl,
 310         s: Span,
 311         defaultness: ast::Defaultness,
 312         inner_attrs: Option<&[ast::Attribute]>,
 313     ) {
 314         let indent = self.block_indent;
 315         let block;
 316         let rewrite = match fk {
 317             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 318                 block = b;
 319                 self.rewrite_fn(
 320                     indent,
 321                     ident,
 322                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 323                     mk_sp(s.lo(), b.span.lo()),
 324                     b,
 325                 )
 326             }
 327             visit::FnKind::Closure(_) => unreachable!(),
 328         };
 329
 330         if let Some(fn_str) = rewrite {
 331             self.format_missing_with_indent(source!(self, s).lo());
 332             self.push_str(&fn_str);
 333             if let Some(c) = fn_str.chars().last() {
 334                 if c == '}' {
 335                     self.last_pos = source!(self, block.span).hi();
 336                     return;
 337                 }
 338             }
 339         } else {
 340             self.format_missing(source!(self, block.span).lo());
 341         }
 342
 343         self.last_pos = source!(self, block.span).lo();
 344         self.visit_block(block, inner_attrs, true)
 345     }
 346
 347     pub fn visit_item(&mut self, item: &ast::Item) {
 348         skip_out_of_file_lines_range_visitor!(self, item.span);
 349
 350         // This is where we bail out if there is a skip attribute. This is only
 351         // complex in the module case. It is complex because the module could be
 352         // in a separate file and there might be attributes in both files, but
 353         // the AST lumps them all together.
 354         let filtered_attrs;
 355         let mut attrs = &item.attrs;
 356         match item.node {
 357             // Module is inline, in this case we treat it like any other item.
 358             _ if !is_mod_decl(item) => {
 359                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 360                     self.push_skipped_with_span(item.span());
 361                     return;
 362                 }
 363             }
 364             // Module is not inline, but should be skipped.
 365             ast::ItemKind::Mod(..) if contains_skip(&item.attrs) => {
 366                 return;
 367             }
 368             // Module is not inline and should not be skipped. We want
 369             // to process only the attributes in the current file.
 370             ast::ItemKind::Mod(..) => {
 371                 filtered_attrs = filter_inline_attrs(&item.attrs, item.span());
 372                 // Assert because if we should skip it should be caught by
 373                 // the above case.
 374                 assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 375                 attrs = &filtered_attrs;
 376             }
 377             _ => {
 378                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 379                     self.push_skipped_with_span(item.span());
 380                     return;
 381                 }
 382             }
 383         }
 384
 385         match item.node {
 386             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 387             ast::ItemKind::Impl(..) => {
 388                 let snippet = self.snippet(item.span);
 389                 let where_span_end = snippet
 390                     .find_uncommented("{")
 391                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 392                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 393                 self.push_rewrite(item.span, rw);
 394             }
 395             ast::ItemKind::Trait(..) => {
 396                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 397                 self.push_rewrite(item.span, rw);
 398             }
 399             ast::ItemKind::TraitAlias(ref generics, ref ty_param_bounds) => {
 400                 let shape = Shape::indented(self.block_indent, self.config);
 401                 let rw = format_trait_alias(
 402                     &self.get_context(),
 403                     item.ident,
 404                     generics,
 405                     ty_param_bounds,
 406                     shape,
 407                 );
 408                 self.push_rewrite(item.span, rw);
 409             }
 410             ast::ItemKind::ExternCrate(_) => {
 411                 let rw = rewrite_extern_crate(&self.get_context(), item);
 412                 self.push_rewrite(item.span, rw);
 413             }
 414             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 415                 self.visit_struct(&StructParts::from_item(item));
 416             }
 417             ast::ItemKind::Enum(ref def, ref generics) => {
 418                 self.format_missing_with_indent(source!(self, item.span).lo());
 419                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 420                 self.last_pos = source!(self, item.span).hi();
 421             }
 422             ast::ItemKind::Mod(ref module) => {
 423                 let is_inline = !is_mod_decl(item);
 424                 self.format_missing_with_indent(source!(self, item.span).lo());
 425                 self.format_mod(module, &item.vis, item.span, item.ident, attrs, is_inline);
 426             }
 427             ast::ItemKind::Mac(ref mac) => {
 428                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 429             }
 430             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 431                 self.format_missing_with_indent(source!(self, item.span).lo());
 432                 self.format_foreign_mod(foreign_mod, item.span);
 433             }
 434             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 435                 self.visit_static(&StaticParts::from_item(item));
 436             }
 437             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 438                 self.visit_fn(
 439                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 440                     generics,
 441                     decl,
 442                     item.span,
 443                     ast::Defaultness::Final,
 444                     Some(&item.attrs),
 445                 )
 446             }
 447             ast::ItemKind::Ty(ref ty, ref generics) => {
 448                 let rewrite = rewrite_type_alias(
 449                     &self.get_context(),
 450                     self.block_indent,
 451                     item.ident,
 452                     ty,
 453                     generics,
 454                     &item.vis,
 455                     item.span,
 456                 );
 457                 self.push_rewrite(item.span, rewrite);
 458             }
 459             ast::ItemKind::GlobalAsm(..) => {
 460                 let snippet = Some(self.snippet(item.span).to_owned());
 461                 self.push_rewrite(item.span, snippet);
 462             }
 463             ast::ItemKind::MacroDef(ref def) => {
 464                 let rewrite = rewrite_macro_def(
 465                     &self.get_context(),
 466                     self.block_indent,
 467                     def,
 468                     item.ident,
 469                     &item.vis,
 470                     item.span,
 471                 );
 472                 self.push_rewrite(item.span, rewrite);
 473             }
 474         }
 475     }
 476
 477     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 478         skip_out_of_file_lines_range_visitor!(self, ti.span);
 479
 480         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 481             self.push_skipped_with_span(ti.span());
 482             return;
 483         }
 484
 485         match ti.node {
 486             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 487             ast::TraitItemKind::Method(ref sig, None) => {
 488                 let indent = self.block_indent;
 489                 let rewrite =
 490                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 491                 self.push_rewrite(ti.span, rewrite);
 492             }
 493             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 494                 self.visit_fn(
 495                     visit::FnKind::Method(ti.ident, sig, None, body),
 496                     &ti.generics,
 497                     &sig.decl,
 498                     ti.span,
 499                     ast::Defaultness::Final,
 500                     Some(&ti.attrs),
 501                 );
 502             }
 503             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 504                 let rewrite = rewrite_associated_type(
 505                     ti.ident,
 506                     type_default.as_ref(),
 507                     Some(type_param_bounds),
 508                     &self.get_context(),
 509                     self.block_indent,
 510                 );
 511                 self.push_rewrite(ti.span, rewrite);
 512             }
 513             ast::TraitItemKind::Macro(ref mac) => {
 514                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 515             }
 516         }
 517     }
 518
 519     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 520         skip_out_of_file_lines_range_visitor!(self, ii.span);
 521
 522         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 523             self.push_skipped_with_span(ii.span());
 524             return;
 525         }
 526
 527         match ii.node {
 528             ast::ImplItemKind::Method(ref sig, ref body) => {
 529                 self.visit_fn(
 530                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 531                     &ii.generics,
 532                     &sig.decl,
 533                     ii.span,
 534                     ii.defaultness,
 535                     Some(&ii.attrs),
 536                 );
 537             }
 538             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 539             ast::ImplItemKind::Type(ref ty) => {
 540                 let rewrite = rewrite_associated_impl_type(
 541                     ii.ident,
 542                     ii.defaultness,
 543                     Some(ty),
 544                     None,
 545                     &self.get_context(),
 546                     self.block_indent,
 547                 );
 548                 self.push_rewrite(ii.span, rewrite);
 549             }
 550             ast::ImplItemKind::Macro(ref mac) => {
 551                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 552             }
 553         }
 554     }
 555
 556     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 557         skip_out_of_file_lines_range_visitor!(self, mac.span);
 558
 559         // 1 = ;
 560         let shape = self.shape().sub_width(1).unwrap();
 561         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 562         self.push_rewrite(mac.span, rewrite);
 563     }
 564
 565     pub fn push_str(&mut self, s: &str) {
 566         self.line_number += count_newlines(s);
 567         self.buffer.push_str(s);
 568     }
 569
 570     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 571         if let Some(ref s) = rewrite {
 572             self.push_str(s);
 573         } else {
 574             let snippet = self.snippet(span);
 575             self.push_str(snippet);
 576         }
 577         self.last_pos = source!(self, span).hi();
 578     }
 579
 580     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 581         self.format_missing_with_indent(source!(self, span).lo());
 582         self.push_rewrite_inner(span, rewrite);
 583     }
 584
 585     pub fn push_skipped_with_span(&mut self, span: Span) {
 586         self.format_missing_with_indent(source!(self, span).lo());
 587         let lo = self.line_number + 1;
 588         self.push_rewrite_inner(span, None);
 589         let hi = self.line_number + 1;
 590         self.skipped_range.push((lo, hi));
 591     }
 592
 593     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 594         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 595     }
 596
 597     pub fn from_codemap(
 598         parse_session: &'a ParseSess,
 599         config: &'a Config,
 600         snippet_provider: &'a SnippetProvider,
 601     ) -> FmtVisitor<'a> {
 602         FmtVisitor {
 603             parse_session,
 604             codemap: parse_session.codemap(),
 605             buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
 606             last_pos: BytePos(0),
 607             block_indent: Indent::empty(),
 608             config,
 609             is_if_else_block: false,
 610             snippet_provider,
 611             line_number: 0,
 612             skipped_range: vec![],
 613         }
 614     }
 615
 616     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 617         self.snippet_provider.span_to_snippet(span)
 618     }
 619
 620     pub fn snippet(&'b self, span: Span) -> &'a str {
 621         self.opt_snippet(span).unwrap()
 622     }
 623
 624     // Returns true if we should skip the following item.
 625     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 626         if contains_skip(attrs) {
 627             return true;
 628         }
 629
 630         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 631         if attrs.is_empty() {
 632             return false;
 633         }
 634
 635         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 636         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 637         self.push_rewrite(span, rewrite);
 638
 639         false
 640     }
 641
 642     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 643     where
 644         F: Fn(&ast::Item) -> bool,
 645     {
 646         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 647         let item_length = items_left
 648             .iter()
 649             .take_while(|ppi| {
 650                 is_item(&***ppi) && (!in_group || {
 651                     let current = self.codemap.lookup_line_range(ppi.span());
 652                     let in_same_group = current.lo < last.hi + 2;
 653                     last = current;
 654                     in_same_group
 655                 })
 656             })
 657             .count();
 658         let items = &items_left[..item_length];
 659
 660         let at_least_one_in_file_lines = items
 661             .iter()
 662             .any(|item| !out_of_file_lines_range!(self, item.span));
 663
 664         if at_least_one_in_file_lines {
 665             self.format_imports(items);
 666         } else {
 667             for item in items {
 668                 self.push_rewrite(item.span, None);
 669             }
 670         }
 671
 672         item_length
 673     }
 674
 675     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 676         macro try_reorder_items_with($reorder: ident, $in_group: ident, $pred: ident) {
 677             if self.config.$reorder() && $pred(&*items_left[0]) {
 678                 let used_items_len =
 679                     self.reorder_items(items_left, &$pred, self.config.$in_group());
 680                 let (_, rest) = items_left.split_at(used_items_len);
 681                 items_left = rest;
 682                 continue;
 683             }
 684         }
 685
 686         while !items_left.is_empty() {
 687             // If the next item is a `use`, `extern crate` or `mod`, then extract it and any
 688             // subsequent items that have the same item kind to be reordered within
 689             // `format_imports`. Otherwise, just format the next item for output.
 690             {
 691                 try_reorder_items_with!(
 692                     reorder_imports,
 693                     reorder_imports_in_group,
 694                     is_use_item_without_attr
 695                 );
 696                 try_reorder_items_with!(
 697                     reorder_extern_crates,
 698                     reorder_extern_crates_in_group,
 699                     is_extern_crate_without_attr
 700                 );
 701                 try_reorder_items_with!(reorder_modules, reorder_modules, is_mod_decl_without_attr);
 702             }
 703             // Reaching here means items were not reordered. There must be at least
 704             // one item left in `items_left`, so calling `unwrap()` here is safe.
 705             let (item, rest) = items_left.split_first().unwrap();
 706             self.visit_item(item);
 707             items_left = rest;
 708         }
 709     }
 710
 711     fn walk_mod_items(&mut self, m: &ast::Mod) {
 712         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 713     }
 714
 715     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 716         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 717             match stmt.node {
 718                 ast::StmtKind::Item(ref item) => Some(&**item),
 719                 _ => None,
 720             }
 721         }
 722
 723         if stmts.is_empty() {
 724             return;
 725         }
 726
 727         // Extract leading `use ...;`.
 728         let items: Vec<_> = stmts
 729             .iter()
 730             .take_while(|stmt| to_stmt_item(stmt).map_or(false, is_use_item))
 731             .filter_map(|stmt| to_stmt_item(stmt))
 732             .collect();
 733
 734         if items.is_empty() {
 735             self.visit_stmt(&stmts[0]);
 736             self.walk_stmts(&stmts[1..]);
 737         } else {
 738             self.walk_items(&items);
 739             self.walk_stmts(&stmts[items.len()..]);
 740         }
 741     }
 742
 743     fn walk_block_stmts(&mut self, b: &ast::Block) {
 744         self.walk_stmts(&b.stmts)
 745     }
 746
 747     fn format_mod(
 748         &mut self,
 749         m: &ast::Mod,
 750         vis: &ast::Visibility,
 751         s: Span,
 752         ident: ast::Ident,
 753         attrs: &[ast::Attribute],
 754         is_internal: bool,
 755     ) {
 756         self.push_str(&*utils::format_visibility(vis));
 757         self.push_str("mod ");
 758         self.push_str(&ident.to_string());
 759
 760         if is_internal {
 761             match self.config.brace_style() {
 762                 BraceStyle::AlwaysNextLine => {
 763                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 764                     self.push_str(&sep_str);
 765                 }
 766                 _ => self.push_str(" {"),
 767             }
 768             // Hackery to account for the closing }.
 769             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 770             let body_snippet =
 771                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 772             let body_snippet = body_snippet.trim();
 773             if body_snippet.is_empty() {
 774                 self.push_str("}");
 775             } else {
 776                 self.last_pos = mod_lo;
 777                 self.block_indent = self.block_indent.block_indent(self.config);
 778                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 779                 self.walk_mod_items(m);
 780                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 781                 self.close_block(false);
 782             }
 783             self.last_pos = source!(self, m.inner).hi();
 784         } else {
 785             self.push_str(";");
 786             self.last_pos = source!(self, s).hi();
 787         }
 788     }
 789
 790     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 791         self.block_indent = Indent::empty();
 792         self.walk_mod_items(m);
 793         self.format_missing_with_indent(filemap.end_pos);
 794     }
 795
 796     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 797         while let Some(pos) = self.codemap
 798             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 799         {
 800             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 801                 if snippet.trim().is_empty() {
 802                     self.last_pos = pos;
 803                 } else {
 804                     return;
 805                 }
 806             }
 807         }
 808     }
 809
 810     pub fn get_context(&self) -> RewriteContext {
 811         RewriteContext {
 812             parse_session: self.parse_session,
 813             codemap: self.codemap,
 814             config: self.config,
 815             inside_macro: false,
 816             use_block: false,
 817             is_if_else_block: false,
 818             force_one_line_chain: false,
 819             snippet_provider: self.snippet_provider,
 820         }
 821     }
 822 }
 823
 824 impl Rewrite for ast::NestedMetaItem {
 825     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 826         match self.node {
 827             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 828             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 829         }
 830     }
 831 }
 832
 833 impl Rewrite for ast::MetaItem {
 834     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 835         Some(match self.node {
 836             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 837             ast::MetaItemKind::List(ref list) => {
 838                 let name = self.name.as_str();
 839                 // 1 = `(`, 2 = `]` and `)`
 840                 let item_shape = shape
 841                     .visual_indent(0)
 842                     .shrink_left(name.len() + 1)
 843                     .and_then(|s| s.sub_width(2))?;
 844                 let items = itemize_list(
 845                     context.codemap,
 846                     list.iter(),
 847                     ")",
 848                     ",",
 849                     |nested_meta_item| nested_meta_item.span.lo(),
 850                     |nested_meta_item| nested_meta_item.span.hi(),
 851                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 852                     self.span.lo(),
 853                     self.span.hi(),
 854                     false,
 855                 );
 856                 let item_vec = items.collect::<Vec<_>>();
 857                 let fmt = ListFormatting {
 858                     tactic: DefinitiveListTactic::Mixed,
 859                     separator: ",",
 860                     trailing_separator: SeparatorTactic::Never,
 861                     separator_place: SeparatorPlace::Back,
 862                     shape: item_shape,
 863                     ends_with_newline: false,
 864                     preserve_newline: false,
 865                     config: context.config,
 866                 };
 867                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 868             }
 869             ast::MetaItemKind::NameValue(ref literal) => {
 870                 let name = self.name.as_str();
 871                 // 3 = ` = `
 872                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 873                 let value = rewrite_literal(context, literal, lit_shape)?;
 874                 format!("{} = {}", name, value)
 875             }
 876         })
 877     }
 878 }
 879
 880 impl Rewrite for ast::Attribute {
 881     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 882         let prefix = match self.style {
 883             ast::AttrStyle::Inner => "#!",
 884             ast::AttrStyle::Outer => "#",
 885         };
 886         let snippet = context.snippet(self.span);
 887         if self.is_sugared_doc {
 888             let doc_shape = Shape {
 889                 width: cmp::min(shape.width, context.config.comment_width())
 890                     .checked_sub(shape.indent.width())
 891                     .unwrap_or(0),
 892                 ..shape
 893             };
 894             rewrite_comment(snippet, false, doc_shape, context.config)
 895         } else {
 896             if contains_comment(snippet) {
 897                 return Some(snippet.to_owned());
 898             }
 899             // 1 = `[`
 900             let shape = shape.offset_left(prefix.len() + 1)?;
 901             self.meta()?
 902                 .rewrite(context, shape)
 903                 .map(|rw| format!("{}[{}]", prefix, rw))
 904         }
 905     }
 906 }
 907
 908 /// Returns the first group of attributes that fills the given predicate.
 909 /// We consider two doc comments are in different group if they are separated by normal comments.
 910 fn take_while_with_pred<'a, P>(
 911     context: &RewriteContext,
 912     attrs: &'a [ast::Attribute],
 913     pred: P,
 914 ) -> &'a [ast::Attribute]
 915 where
 916     P: Fn(&ast::Attribute) -> bool,
 917 {
 918     let mut last_index = 0;
 919     let mut iter = attrs.iter().enumerate().peekable();
 920     while let Some((i, attr)) = iter.next() {
 921         if !pred(attr) {
 922             break;
 923         }
 924         if let Some(&(_, next_attr)) = iter.peek() {
 925             // Extract comments between two attributes.
 926             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 927             let snippet = context.snippet(span_between_attr);
 928             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 929                 break;
 930             }
 931         }
 932         last_index = i;
 933     }
 934     if last_index == 0 {
 935         &[]
 936     } else {
 937         &attrs[..last_index + 1]
 938     }
 939 }
 940
 941 fn rewrite_first_group_attrs(
 942     context: &RewriteContext,
 943     attrs: &[ast::Attribute],
 944     shape: Shape,
 945 ) -> Option<(usize, String)> {
 946     if attrs.is_empty() {
 947         return Some((0, String::new()));
 948     }
 949     // Rewrite doc comments
 950     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 951     if !sugared_docs.is_empty() {
 952         let snippet = sugared_docs
 953             .iter()
 954             .map(|a| context.snippet(a.span))
 955             .collect::<Vec<_>>()
 956             .join("\n");
 957         return Some((
 958             sugared_docs.len(),
 959             rewrite_comment(&snippet, false, shape, context.config)?,
 960         ));
 961     }
 962     // Rewrite `#[derive(..)]`s.
 963     if context.config.merge_derives() {
 964         let derives = take_while_with_pred(context, attrs, is_derive);
 965         if !derives.is_empty() {
 966             let mut derive_args = vec![];
 967             for derive in derives {
 968                 derive_args.append(&mut get_derive_args(context, derive)?);
 969             }
 970             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 971         }
 972     }
 973     // Rewrite the first attribute.
 974     Some((1, attrs[0].rewrite(context, shape)?))
 975 }
 976
 977 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 978     // Look at before and after comment and see if there are any empty lines.
 979     let comment_begin = comment.chars().position(|c| c == '/');
 980     let len = comment_begin.unwrap_or_else(|| comment.len());
 981     let mlb = count_newlines(&comment[..len]) > 1;
 982     let mla = if comment_begin.is_none() {
 983         mlb
 984     } else {
 985         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 986         let len = comment_end.unwrap();
 987         comment
 988             .chars()
 989             .rev()
 990             .take(len)
 991             .filter(|c| *c == '\n')
 992             .count() > 1
 993     };
 994     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 995 }
 996
 997 impl<'a> Rewrite for [ast::Attribute] {
 998     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 999         if self.is_empty() {
1000             return Some(String::new());
1001         }
1002         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
1003         if self.len() == 1 || first_group_len == self.len() {
1004             Some(first_group_str)
1005         } else {
1006             let rest_str = self[first_group_len..].rewrite(context, shape)?;
1007             let missing_span = mk_sp(
1008                 self[first_group_len - 1].span.hi(),
1009                 self[first_group_len].span.lo(),
1010             );
1011             // Preserve an empty line before/after doc comments.
1012             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
1013                 let snippet = context.snippet(missing_span);
1014                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
1015                 let comment = ::comment::recover_missing_comment_in_span(
1016                     missing_span,
1017                     shape.with_max_width(context.config),
1018                     context,
1019                     0,
1020                 )?;
1021                 let comment = if comment.is_empty() {
1022                     format!("\n{}", mlb)
1023                 } else {
1024                     format!("{}{}\n{}", mla, comment, mlb)
1025                 };
1026                 Some(format!(
1027                     "{}{}{}{}",
1028                     first_group_str,
1029                     comment,
1030                     shape.indent.to_string(context.config),
1031                     rest_str
1032                 ))
1033             } else {
1034                 combine_strs_with_missing_comments(
1035                     context,
1036                     &first_group_str,
1037                     &rest_str,
1038                     missing_span,
1039                     shape,
1040                     false,
1041                 )
1042             }
1043         }
1044     }
1045 }
1046
1047 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1048 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1049     let mut result = String::with_capacity(128);
1050     result.push_str("#[derive(");
1051     // 11 = `#[derive()]`
1052     let initial_budget = shape.width.checked_sub(11)?;
1053     let mut budget = initial_budget;
1054     let num = derive_args.len();
1055     for (i, a) in derive_args.iter().enumerate() {
1056         // 2 = `, ` or `)]`
1057         let width = a.len() + 2;
1058         if width > budget {
1059             if i > 0 {
1060                 // Remove trailing whitespace.
1061                 result.pop();
1062             }
1063             result.push('\n');
1064             // 9 = `#[derive(`
1065             result.push_str(&(shape.indent + 9).to_string(context.config));
1066             budget = initial_budget;
1067         } else {
1068             budget = budget.checked_sub(width).unwrap_or(0);
1069         }
1070         result.push_str(a);
1071         if i != num - 1 {
1072             result.push_str(", ")
1073         }
1074     }
1075     result.push_str(")]");
1076     Some(result)
1077 }
1078
1079 fn is_derive(attr: &ast::Attribute) -> bool {
1080     attr.check_name("derive")
1081 }
1082
1083 /// Returns the arguments of `#[derive(...)]`.
1084 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1085     attr.meta_item_list().map(|meta_item_list| {
1086         meta_item_list
1087             .iter()
1088             .map(|nested_meta_item| context.snippet(nested_meta_item.span))
1089             .collect()
1090     })
1091 }
1092
1093 // Rewrite `extern crate foo;` WITHOUT attributes.
1094 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1095     assert!(is_extern_crate(item));
1096     let new_str = context.snippet(item.span);
1097     Some(if contains_comment(new_str) {
1098         new_str.to_owned()
1099     } else {
1100         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1101         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1102     })
1103 }
1104
1105 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1106     match stmt.node {
1107         ast::StmtKind::Local(ref local) => &local.attrs,
1108         ast::StmtKind::Item(ref item) => &item.attrs,
1109         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1110         ast::StmtKind::Mac(ref mac) => &mac.2,
1111     }
1112 }