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 strings::string_buffer::StringBuffer;
  14 use syntax::{ast, ptr, visit};
  15 use syntax::attr::HasAttrs;
  16 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  17 use syntax::parse::ParseSess;
  18
  19 use {Indent, Shape, Spanned};
  20 use codemap::{LineRangeUtils, SpanUtils};
  21 use comment::{contains_comment, recover_missing_comment_in_span, CodeCharKind, CommentCodeSlices,
  22               FindUncommented};
  23 use comment::rewrite_comment;
  24 use config::{BraceStyle, Config};
  25 use items::{format_impl, format_struct, format_struct_struct, format_trait,
  26             rewrite_associated_impl_type, rewrite_associated_type, rewrite_static,
  27             rewrite_type_alias};
  28 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  29             SeparatorTactic};
  30 use macros::{rewrite_macro, MacroPosition};
  31 use regex::Regex;
  32 use rewrite::{Rewrite, RewriteContext};
  33 use utils::{self, contains_skip, inner_attributes, mk_sp};
  34
  35 fn is_use_item(item: &ast::Item) -> bool {
  36     match item.node {
  37         ast::ItemKind::Use(_) => true,
  38         _ => false,
  39     }
  40 }
  41
  42 fn is_extern_crate(item: &ast::Item) -> bool {
  43     match item.node {
  44         ast::ItemKind::ExternCrate(..) => true,
  45         _ => false,
  46     }
  47 }
  48
  49 pub struct FmtVisitor<'a> {
  50     pub parse_session: &'a ParseSess,
  51     pub codemap: &'a CodeMap,
  52     pub buffer: StringBuffer,
  53     pub last_pos: BytePos,
  54     // FIXME: use an RAII util or closure for indenting
  55     pub block_indent: Indent,
  56     pub config: &'a Config,
  57     pub is_if_else_block: bool,
  58 }
  59
  60 impl<'a> FmtVisitor<'a> {
  61     pub fn shape(&self) -> Shape {
  62         Shape::indented(self.block_indent, self.config)
  63     }
  64
  65     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  66         debug!(
  67             "visit_stmt: {:?} {:?}",
  68             self.codemap.lookup_char_pos(stmt.span.lo()),
  69             self.codemap.lookup_char_pos(stmt.span.hi())
  70         );
  71
  72         match stmt.node {
  73             ast::StmtKind::Item(ref item) => {
  74                 self.visit_item(item);
  75             }
  76             ast::StmtKind::Local(..) => {
  77                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  78                 self.push_rewrite(stmt.span(), rewrite);
  79             }
  80             ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  81                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  82                 self.push_rewrite(stmt.span(), rewrite)
  83             }
  84             ast::StmtKind::Mac(ref mac) => {
  85                 let (ref mac, _macro_style, ref attrs) = **mac;
  86                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  87                     self.push_rewrite(stmt.span(), None);
  88                 } else {
  89                     self.visit_mac(mac, None, MacroPosition::Statement);
  90                 }
  91                 self.format_missing(stmt.span.hi());
  92             }
  93         }
  94     }
  95
  96     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
  97         debug!(
  98             "visit_block: {:?} {:?}",
  99             self.codemap.lookup_char_pos(b.span.lo()),
 100             self.codemap.lookup_char_pos(b.span.hi())
 101         );
 102
 103         // Check if this block has braces.
 104         let snippet = self.snippet(b.span);
 105         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 106         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 107
 108         self.last_pos = self.last_pos + brace_compensation;
 109         self.block_indent = self.block_indent.block_indent(self.config);
 110         self.buffer.push_str("{");
 111
 112         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 113             if let Some(first_stmt) = b.stmts.first() {
 114                 let attr_lo = inner_attrs
 115                     .and_then(|attrs| {
 116                         inner_attributes(attrs).first().map(|attr| attr.span.lo())
 117                     })
 118                     .or_else(|| {
 119                         // Attributes for an item in a statement position
 120                         // do not belong to the statement. (rust-lang/rust#34459)
 121                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 122                             item.attrs.first()
 123                         } else {
 124                             first_stmt.attrs().first()
 125                         }.and_then(|attr| {
 126                             // Some stmts can have embedded attributes.
 127                             // e.g. `match { #![attr] ... }`
 128                             let attr_lo = attr.span.lo();
 129                             if attr_lo < first_stmt.span.lo() {
 130                                 Some(attr_lo)
 131                             } else {
 132                                 None
 133                             }
 134                         })
 135                     });
 136
 137                 let snippet = self.snippet(mk_sp(
 138                     self.last_pos,
 139                     attr_lo.unwrap_or(first_stmt.span.lo()),
 140                 ));
 141                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 142                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 143                         s.rfind('\n')
 144                     } else {
 145                         None
 146                     },
 147                 );
 148                 if let Some(len) = len {
 149                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 150                 }
 151             }
 152         }
 153
 154         // Format inner attributes if available.
 155         if let Some(attrs) = inner_attrs {
 156             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 157         }
 158
 159         for stmt in &b.stmts {
 160             self.visit_stmt(stmt)
 161         }
 162
 163         if !b.stmts.is_empty() {
 164             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 165                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 166                     self.buffer.push_str(";");
 167                 }
 168             }
 169         }
 170
 171         let mut remove_len = BytePos(0);
 172         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 173             if let Some(stmt) = b.stmts.last() {
 174                 let snippet = self.snippet(mk_sp(
 175                     stmt.span.hi(),
 176                     source!(self, b.span).hi() - brace_compensation,
 177                 ));
 178                 let len = CommentCodeSlices::new(&snippet)
 179                     .last()
 180                     .and_then(|(kind, _, s)| {
 181                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 182                             Some(s.len())
 183                         } else {
 184                             None
 185                         }
 186                     });
 187                 if let Some(len) = len {
 188                     remove_len = BytePos::from_usize(len);
 189                 }
 190             }
 191         }
 192
 193         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 194         if unindent_comment {
 195             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 196             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 197             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 198         }
 199         // FIXME: we should compress any newlines here to just one
 200         if unindent_comment {
 201             self.block_indent = self.block_indent.block_unindent(self.config);
 202         }
 203         self.format_missing_with_indent(
 204             source!(self, b.span).hi() - brace_compensation - remove_len,
 205         );
 206         if unindent_comment {
 207             self.block_indent = self.block_indent.block_indent(self.config);
 208         }
 209         self.close_block(unindent_comment);
 210         self.last_pos = source!(self, b.span).hi();
 211     }
 212
 213     // FIXME: this is a terrible hack to indent the comments between the last
 214     // item in the block and the closing brace to the block's level.
 215     // The closing brace itself, however, should be indented at a shallower
 216     // level.
 217     fn close_block(&mut self, unindent_comment: bool) {
 218         let total_len = self.buffer.len;
 219         let chars_too_many = if unindent_comment {
 220             0
 221         } else if self.config.hard_tabs() {
 222             1
 223         } else {
 224             self.config.tab_spaces()
 225         };
 226         self.buffer.truncate(total_len - chars_too_many);
 227         self.buffer.push_str("}");
 228         self.block_indent = self.block_indent.block_unindent(self.config);
 229     }
 230
 231     // Note that this only gets called for function definitions. Required methods
 232     // on traits do not get handled here.
 233     fn visit_fn(
 234         &mut self,
 235         fk: visit::FnKind,
 236         fd: &ast::FnDecl,
 237         s: Span,
 238         _: ast::NodeId,
 239         defaultness: ast::Defaultness,
 240         inner_attrs: Option<&[ast::Attribute]>,
 241     ) {
 242         let indent = self.block_indent;
 243         let block;
 244         let rewrite = match fk {
 245             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 246                 block = b;
 247                 self.rewrite_fn(
 248                     indent,
 249                     ident,
 250                     fd,
 251                     generics,
 252                     unsafety,
 253                     constness.node,
 254                     defaultness,
 255                     abi,
 256                     vis,
 257                     mk_sp(s.lo(), b.span.lo()),
 258                     b,
 259                 )
 260             }
 261             visit::FnKind::Method(ident, sig, vis, b) => {
 262                 block = b;
 263                 self.rewrite_fn(
 264                     indent,
 265                     ident,
 266                     fd,
 267                     &sig.generics,
 268                     sig.unsafety,
 269                     sig.constness.node,
 270                     defaultness,
 271                     sig.abi,
 272                     vis.unwrap_or(&ast::Visibility::Inherited),
 273                     mk_sp(s.lo(), b.span.lo()),
 274                     b,
 275                 )
 276             }
 277             visit::FnKind::Closure(_) => unreachable!(),
 278         };
 279
 280         if let Some(fn_str) = rewrite {
 281             self.format_missing_with_indent(source!(self, s).lo());
 282             self.buffer.push_str(&fn_str);
 283             if let Some(c) = fn_str.chars().last() {
 284                 if c == '}' {
 285                     self.last_pos = source!(self, block.span).hi();
 286                     return;
 287                 }
 288             }
 289         } else {
 290             self.format_missing(source!(self, block.span).lo());
 291         }
 292
 293         self.last_pos = source!(self, block.span).lo();
 294         self.visit_block(block, inner_attrs)
 295     }
 296
 297     pub fn visit_item(&mut self, item: &ast::Item) {
 298         skip_out_of_file_lines_range_visitor!(self, item.span);
 299
 300         // This is where we bail out if there is a skip attribute. This is only
 301         // complex in the module case. It is complex because the module could be
 302         // in a separate file and there might be attributes in both files, but
 303         // the AST lumps them all together.
 304         let filterd_attrs;
 305         let mut attrs = &item.attrs;
 306         match item.node {
 307             ast::ItemKind::Mod(ref m) => {
 308                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 309                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 310                 if outer_file.name == inner_file.name {
 311                     // Module is inline, in this case we treat modules like any
 312                     // other item.
 313                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 314                         self.push_rewrite(item.span, None);
 315                         return;
 316                     }
 317                 } else if contains_skip(&item.attrs) {
 318                     // Module is not inline, but should be skipped.
 319                     return;
 320                 } else {
 321                     // Module is not inline and should not be skipped. We want
 322                     // to process only the attributes in the current file.
 323                     filterd_attrs = item.attrs
 324                         .iter()
 325                         .filter_map(|a| {
 326                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 327                             if attr_file.name == outer_file.name {
 328                                 Some(a.clone())
 329                             } else {
 330                                 None
 331                             }
 332                         })
 333                         .collect::<Vec<_>>();
 334                     // Assert because if we should skip it should be caught by
 335                     // the above case.
 336                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 337                     attrs = &filterd_attrs;
 338                 }
 339             }
 340             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 341                 self.push_rewrite(item.span, None);
 342                 return;
 343             },
 344         }
 345
 346         match item.node {
 347             ast::ItemKind::Use(ref vp) => self.format_import(&item, vp),
 348             ast::ItemKind::Impl(..) => {
 349                 let snippet = self.snippet(item.span);
 350                 let where_span_end = snippet
 351                     .find_uncommented("{")
 352                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 353                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 354                 self.push_rewrite(item.span, rw);
 355             }
 356             ast::ItemKind::Trait(..) => {
 357                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 358                 self.push_rewrite(item.span, rw);
 359             }
 360             ast::ItemKind::ExternCrate(_) => {
 361                 let rw = rewrite_extern_crate(&self.get_context(), item);
 362                 self.push_rewrite(item.span, rw);
 363             }
 364             ast::ItemKind::Struct(ref def, ref generics) => {
 365                 let rewrite = format_struct(
 366                     &self.get_context(),
 367                     "struct ",
 368                     item.ident,
 369                     &item.vis,
 370                     def,
 371                     Some(generics),
 372                     item.span,
 373                     self.block_indent,
 374                     None,
 375                 ).map(|s| match *def {
 376                     ast::VariantData::Tuple(..) => s + ";",
 377                     _ => s,
 378                 });
 379                 self.push_rewrite(item.span, rewrite);
 380             }
 381             ast::ItemKind::Enum(ref def, ref generics) => {
 382                 self.format_missing_with_indent(source!(self, item.span).lo());
 383                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 384                 self.last_pos = source!(self, item.span).hi();
 385             }
 386             ast::ItemKind::Mod(ref module) => {
 387                 self.format_missing_with_indent(source!(self, item.span).lo());
 388                 self.format_mod(module, &item.vis, item.span, item.ident, &attrs);
 389             }
 390             ast::ItemKind::Mac(ref mac) => {
 391                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 392             }
 393             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 394                 self.format_missing_with_indent(source!(self, item.span).lo());
 395                 self.format_foreign_mod(foreign_mod, item.span);
 396             }
 397             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 398                 let rewrite = rewrite_static(
 399                     "static",
 400                     &item.vis,
 401                     item.ident,
 402                     ty,
 403                     mutability,
 404                     Some(expr),
 405                     self.block_indent,
 406                     item.span,
 407                     &self.get_context(),
 408                 );
 409                 self.push_rewrite(item.span, rewrite);
 410             }
 411             ast::ItemKind::Const(ref ty, ref expr) => {
 412                 let rewrite = rewrite_static(
 413                     "const",
 414                     &item.vis,
 415                     item.ident,
 416                     ty,
 417                     ast::Mutability::Immutable,
 418                     Some(expr),
 419                     self.block_indent,
 420                     item.span,
 421                     &self.get_context(),
 422                 );
 423                 self.push_rewrite(item.span, rewrite);
 424             }
 425             ast::ItemKind::DefaultImpl(..) => {
 426                 // FIXME(#78): format impl definitions.
 427             }
 428             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 429                 self.visit_fn(
 430                     visit::FnKind::ItemFn(
 431                         item.ident,
 432                         generics,
 433                         unsafety,
 434                         constness,
 435                         abi,
 436                         &item.vis,
 437                         body,
 438                     ),
 439                     decl,
 440                     item.span,
 441                     item.id,
 442                     ast::Defaultness::Final,
 443                     Some(&item.attrs),
 444                 )
 445             }
 446             ast::ItemKind::Ty(ref ty, ref generics) => {
 447                 let rewrite = rewrite_type_alias(
 448                     &self.get_context(),
 449                     self.block_indent,
 450                     item.ident,
 451                     ty,
 452                     generics,
 453                     &item.vis,
 454                     item.span,
 455                 );
 456                 self.push_rewrite(item.span, rewrite);
 457             }
 458             ast::ItemKind::Union(ref def, ref generics) => {
 459                 let rewrite = format_struct_struct(
 460                     &self.get_context(),
 461                     "union ",
 462                     item.ident,
 463                     &item.vis,
 464                     def.fields(),
 465                     Some(generics),
 466                     item.span,
 467                     self.block_indent,
 468                     None,
 469                 );
 470                 self.push_rewrite(item.span, rewrite);
 471             }
 472             ast::ItemKind::GlobalAsm(..) => {
 473                 let snippet = Some(self.snippet(item.span));
 474                 self.push_rewrite(item.span, snippet);
 475             }
 476             ast::ItemKind::MacroDef(..) => {
 477                 // FIXME(#1539): macros 2.0
 478                 let mac_snippet = Some(self.snippet(item.span));
 479                 self.push_rewrite(item.span, mac_snippet);
 480             }
 481         }
 482     }
 483
 484     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 485         skip_out_of_file_lines_range_visitor!(self, ti.span);
 486
 487         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 488             self.push_rewrite(ti.span, None);
 489             return;
 490         }
 491
 492         match ti.node {
 493             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 494                 let rewrite = rewrite_static(
 495                     "const",
 496                     &ast::Visibility::Inherited,
 497                     ti.ident,
 498                     ty,
 499                     ast::Mutability::Immutable,
 500                     expr_opt.as_ref(),
 501                     self.block_indent,
 502                     ti.span,
 503                     &self.get_context(),
 504                 );
 505                 self.push_rewrite(ti.span, rewrite);
 506             }
 507             ast::TraitItemKind::Method(ref sig, None) => {
 508                 let indent = self.block_indent;
 509                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 510                 self.push_rewrite(ti.span, rewrite);
 511             }
 512             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 513                 self.visit_fn(
 514                     visit::FnKind::Method(ti.ident, sig, None, body),
 515                     &sig.decl,
 516                     ti.span,
 517                     ti.id,
 518                     ast::Defaultness::Final,
 519                     Some(&ti.attrs),
 520                 );
 521             }
 522             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 523                 let rewrite = rewrite_associated_type(
 524                     ti.ident,
 525                     type_default.as_ref(),
 526                     Some(type_param_bounds),
 527                     &self.get_context(),
 528                     self.block_indent,
 529                 );
 530                 self.push_rewrite(ti.span, rewrite);
 531             }
 532             ast::TraitItemKind::Macro(ref mac) => {
 533                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 534             }
 535         }
 536     }
 537
 538     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 539         skip_out_of_file_lines_range_visitor!(self, ii.span);
 540
 541         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 542             self.push_rewrite(ii.span, None);
 543             return;
 544         }
 545
 546         match ii.node {
 547             ast::ImplItemKind::Method(ref sig, ref body) => {
 548                 self.visit_fn(
 549                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 550                     &sig.decl,
 551                     ii.span,
 552                     ii.id,
 553                     ii.defaultness,
 554                     Some(&ii.attrs),
 555                 );
 556             }
 557             ast::ImplItemKind::Const(ref ty, ref expr) => {
 558                 let rewrite = rewrite_static(
 559                     "const",
 560                     &ii.vis,
 561                     ii.ident,
 562                     ty,
 563                     ast::Mutability::Immutable,
 564                     Some(expr),
 565                     self.block_indent,
 566                     ii.span,
 567                     &self.get_context(),
 568                 );
 569                 self.push_rewrite(ii.span, rewrite);
 570             }
 571             ast::ImplItemKind::Type(ref ty) => {
 572                 let rewrite = rewrite_associated_impl_type(
 573                     ii.ident,
 574                     ii.defaultness,
 575                     Some(ty),
 576                     None,
 577                     &self.get_context(),
 578                     self.block_indent,
 579                 );
 580                 self.push_rewrite(ii.span, rewrite);
 581             }
 582             ast::ImplItemKind::Macro(ref mac) => {
 583                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 584             }
 585         }
 586     }
 587
 588     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 589         skip_out_of_file_lines_range_visitor!(self, mac.span);
 590
 591         // 1 = ;
 592         let shape = self.shape().sub_width(1).unwrap();
 593         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 594         self.push_rewrite(mac.span, rewrite);
 595     }
 596
 597     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 598         self.format_missing_with_indent(source!(self, span).lo());
 599         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 600         self.buffer.push_str(&result);
 601         self.last_pos = source!(self, span).hi();
 602     }
 603
 604     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 605         FmtVisitor {
 606             parse_session: parse_session,
 607             codemap: parse_session.codemap(),
 608             buffer: StringBuffer::new(),
 609             last_pos: BytePos(0),
 610             block_indent: Indent::empty(),
 611             config: config,
 612             is_if_else_block: false,
 613         }
 614     }
 615
 616     pub fn snippet(&self, span: Span) -> String {
 617         match self.codemap.span_to_snippet(span) {
 618             Ok(s) => s,
 619             Err(_) => {
 620                 println!(
 621                     "Couldn't make snippet for span {:?}->{:?}",
 622                     self.codemap.lookup_char_pos(span.lo()),
 623                     self.codemap.lookup_char_pos(span.hi())
 624                 );
 625                 "".to_owned()
 626             }
 627         }
 628     }
 629
 630     // Returns true if we should skip the following item.
 631     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 632         if contains_skip(attrs) {
 633             return true;
 634         }
 635
 636         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 637         if attrs.is_empty() {
 638             return false;
 639         }
 640
 641         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 642         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 643         self.push_rewrite(span, rewrite);
 644
 645         false
 646     }
 647
 648     fn reorder_items<F>(
 649         &mut self,
 650         items_left: &[ptr::P<ast::Item>],
 651         is_item: &F,
 652         in_group: bool,
 653     ) -> usize
 654     where
 655         F: Fn(&ast::Item) -> bool,
 656     {
 657         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 658         let item_length = items_left
 659             .iter()
 660             .take_while(|ppi| {
 661                 is_item(&***ppi) && (!in_group || {
 662                     let current = self.codemap.lookup_line_range(ppi.span());
 663                     let in_same_group = current.lo < last.hi + 2;
 664                     last = current;
 665                     in_same_group
 666                 })
 667             })
 668             .count();
 669         let items = &items_left[..item_length];
 670
 671         let at_least_one_in_file_lines = items
 672             .iter()
 673             .any(|item| !out_of_file_lines_range!(self, item.span));
 674
 675         if at_least_one_in_file_lines {
 676             self.format_imports(items);
 677         } else {
 678             for item in items {
 679                 self.push_rewrite(item.span, None);
 680             }
 681         }
 682
 683         item_length
 684     }
 685
 686     fn walk_mod_items(&mut self, m: &ast::Mod) {
 687         let mut items_left: &[ptr::P<ast::Item>] = &m.items;
 688         while !items_left.is_empty() {
 689             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 690             // to be potentially reordered within `format_imports`. Otherwise, just format the
 691             // next item for output.
 692             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 693                 let used_items_len = self.reorder_items(
 694                     items_left,
 695                     &is_use_item,
 696                     self.config.reorder_imports_in_group(),
 697                 );
 698                 let (_, rest) = items_left.split_at(used_items_len);
 699                 items_left = rest;
 700             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 701                 let used_items_len = self.reorder_items(
 702                     items_left,
 703                     &is_extern_crate,
 704                     self.config.reorder_extern_crates_in_group(),
 705                 );
 706                 let (_, rest) = items_left.split_at(used_items_len);
 707                 items_left = rest;
 708             } else {
 709                 // `unwrap()` is safe here because we know `items_left`
 710                 // has elements from the loop condition
 711                 let (item, rest) = items_left.split_first().unwrap();
 712                 self.visit_item(item);
 713                 items_left = rest;
 714             }
 715         }
 716     }
 717
 718     fn format_mod(
 719         &mut self,
 720         m: &ast::Mod,
 721         vis: &ast::Visibility,
 722         s: Span,
 723         ident: ast::Ident,
 724         attrs: &[ast::Attribute],
 725     ) {
 726         // Decide whether this is an inline mod or an external mod.
 727         let local_file_name = self.codemap.span_to_filename(s);
 728         let inner_span = source!(self, m.inner);
 729         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0) &&
 730             local_file_name == self.codemap.span_to_filename(inner_span);
 731
 732         self.buffer.push_str(&*utils::format_visibility(vis));
 733         self.buffer.push_str("mod ");
 734         self.buffer.push_str(&ident.to_string());
 735
 736         if is_internal {
 737             match self.config.item_brace_style() {
 738                 BraceStyle::AlwaysNextLine => self.buffer
 739                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 740                 _ => self.buffer.push_str(" {"),
 741             }
 742             // Hackery to account for the closing }.
 743             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 744             let body_snippet =
 745                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 746             let body_snippet = body_snippet.trim();
 747             if body_snippet.is_empty() {
 748                 self.buffer.push_str("}");
 749             } else {
 750                 self.last_pos = mod_lo;
 751                 self.block_indent = self.block_indent.block_indent(self.config);
 752                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 753                 self.walk_mod_items(m);
 754                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 755                 self.close_block(false);
 756             }
 757             self.last_pos = source!(self, m.inner).hi();
 758         } else {
 759             self.buffer.push_str(";");
 760             self.last_pos = source!(self, s).hi();
 761         }
 762     }
 763
 764     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 765         self.block_indent = Indent::empty();
 766         self.walk_mod_items(m);
 767         self.format_missing_with_indent(filemap.end_pos);
 768     }
 769
 770     pub fn get_context(&self) -> RewriteContext {
 771         RewriteContext {
 772             parse_session: self.parse_session,
 773             codemap: self.codemap,
 774             config: self.config,
 775             inside_macro: false,
 776             use_block: false,
 777             is_if_else_block: false,
 778             force_one_line_chain: false,
 779         }
 780     }
 781 }
 782
 783 impl Rewrite for ast::NestedMetaItem {
 784     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 785         match self.node {
 786             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 787             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 788         }
 789     }
 790 }
 791
 792 impl Rewrite for ast::MetaItem {
 793     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 794         Some(match self.node {
 795             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 796             ast::MetaItemKind::List(ref list) => {
 797                 let name = self.name.as_str();
 798                 // 3 = `#[` and `(`, 2 = `]` and `)`
 799                 let item_shape = try_opt!(
 800                     shape
 801                         .shrink_left(name.len() + 3)
 802                         .and_then(|s| s.sub_width(2))
 803                 );
 804                 let items = itemize_list(
 805                     context.codemap,
 806                     list.iter(),
 807                     ")",
 808                     |nested_meta_item| nested_meta_item.span.lo(),
 809                     |nested_meta_item| nested_meta_item.span.hi(),
 810                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 811                     self.span.lo(),
 812                     self.span.hi(),
 813                     false,
 814                 );
 815                 let item_vec = items.collect::<Vec<_>>();
 816                 let fmt = ListFormatting {
 817                     tactic: DefinitiveListTactic::Mixed,
 818                     separator: ",",
 819                     trailing_separator: SeparatorTactic::Never,
 820                     separator_place: SeparatorPlace::Back,
 821                     shape: item_shape,
 822                     ends_with_newline: false,
 823                     preserve_newline: false,
 824                     config: context.config,
 825                 };
 826                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 827             }
 828             ast::MetaItemKind::NameValue(ref literal) => {
 829                 let name = self.name.as_str();
 830                 let value = context.snippet(literal.span);
 831                 if &*name == "doc" && contains_comment(&value) {
 832                     let doc_shape = Shape {
 833                         width: cmp::min(shape.width, context.config.comment_width())
 834                             .checked_sub(shape.indent.width())
 835                             .unwrap_or(0),
 836                         ..shape
 837                     };
 838                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 839                 } else {
 840                     format!("{} = {}", name, value)
 841                 }
 842             }
 843         })
 844     }
 845 }
 846
 847 impl Rewrite for ast::Attribute {
 848     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 849         try_opt!(self.meta())
 850             .rewrite(context, shape)
 851             .map(|rw| if self.is_sugared_doc {
 852                 rw
 853             } else {
 854                 let original = context.snippet(self.span);
 855                 let prefix = match self.style {
 856                     ast::AttrStyle::Inner => "#!",
 857                     ast::AttrStyle::Outer => "#",
 858                 };
 859                 if contains_comment(&original) {
 860                     original
 861                 } else {
 862                     format!("{}[{}]", prefix, rw)
 863                 }
 864             })
 865     }
 866 }
 867
 868 impl<'a> Rewrite for [ast::Attribute] {
 869     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 870         if self.is_empty() {
 871             return Some(String::new());
 872         }
 873         let mut result = String::with_capacity(128);
 874         let indent = shape.indent.to_string(context.config);
 875
 876         let mut derive_args = Vec::new();
 877
 878         let mut iter = self.iter().enumerate().peekable();
 879         let mut insert_new_line = true;
 880         let mut is_prev_sugared_doc = false;
 881         while let Some((i, a)) = iter.next() {
 882             let a_str = try_opt!(a.rewrite(context, shape));
 883
 884             // Write comments and blank lines between attributes.
 885             if i > 0 {
 886                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 887                 // This particular horror show is to preserve line breaks in between doc
 888                 // comments. An alternative would be to force such line breaks to start
 889                 // with the usual doc comment token.
 890                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc ||
 891                     is_prev_sugared_doc
 892                 {
 893                     // Look at before and after comment and see if there are any empty lines.
 894                     let comment_begin = comment.chars().position(|c| c == '/');
 895                     let len = comment_begin.unwrap_or_else(|| comment.len());
 896                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 897                     let mla = if comment_begin.is_none() {
 898                         mlb
 899                     } else {
 900                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 901                         let len = comment_end.unwrap();
 902                         comment
 903                             .chars()
 904                             .rev()
 905                             .take(len)
 906                             .filter(|c| *c == '\n')
 907                             .count() > 1
 908                     };
 909                     (mlb, mla)
 910                 } else {
 911                     (false, false)
 912                 };
 913
 914                 let comment = try_opt!(recover_missing_comment_in_span(
 915                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 916                     shape.with_max_width(context.config),
 917                     context,
 918                     0,
 919                 ));
 920
 921                 if !comment.is_empty() {
 922                     if multi_line_before {
 923                         result.push('\n');
 924                     }
 925                     result.push_str(&comment);
 926                     result.push('\n');
 927                     if multi_line_after {
 928                         result.push('\n')
 929                     }
 930                 } else if insert_new_line {
 931                     result.push('\n');
 932                     if multi_line_after {
 933                         result.push('\n')
 934                     }
 935                 }
 936
 937                 if derive_args.is_empty() {
 938                     result.push_str(&indent);
 939                 }
 940
 941                 insert_new_line = true;
 942             }
 943
 944             // Write the attribute itself.
 945             if context.config.merge_derives() {
 946                 // If the attribute is `#[derive(...)]`, take the arguments.
 947                 if let Some(mut args) = get_derive_args(context, a) {
 948                     derive_args.append(&mut args);
 949                     match iter.peek() {
 950                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 951                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 952                         // If not, rewrite the merged derives.
 953                         _ => {
 954                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 955                             derive_args.clear();
 956                         }
 957                     }
 958                 } else {
 959                     result.push_str(&a_str);
 960                 }
 961             } else {
 962                 result.push_str(&a_str);
 963             }
 964
 965             is_prev_sugared_doc = a.is_sugared_doc;
 966         }
 967         Some(result)
 968     }
 969 }
 970
 971 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 972 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 973     let mut result = String::with_capacity(128);
 974     result.push_str("#[derive(");
 975     // 11 = `#[derive()]`
 976     let initial_budget = try_opt!(shape.width.checked_sub(11));
 977     let mut budget = initial_budget;
 978     let num = derive_args.len();
 979     for (i, a) in derive_args.iter().enumerate() {
 980         // 2 = `, ` or `)]`
 981         let width = a.len() + 2;
 982         if width > budget {
 983             if i > 0 {
 984                 // Remove trailing whitespace.
 985                 result.pop();
 986             }
 987             result.push('\n');
 988             // 9 = `#[derive(`
 989             result.push_str(&(shape.indent + 9).to_string(context.config));
 990             budget = initial_budget;
 991         } else {
 992             budget = budget.checked_sub(width).unwrap_or(0);
 993         }
 994         result.push_str(a);
 995         if i != num - 1 {
 996             result.push_str(", ")
 997         }
 998     }
 999     result.push_str(")]");
1000     Some(result)
1001 }
1002
1003 fn is_derive(attr: &ast::Attribute) -> bool {
1004     match attr.meta() {
1005         Some(meta_item) => match meta_item.node {
1006             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1007             _ => false,
1008         },
1009         _ => false,
1010     }
1011 }
1012
1013 /// Returns the arguments of `#[derive(...)]`.
1014 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1015     attr.meta().and_then(|meta_item| match meta_item.node {
1016         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1017             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1018             Some(
1019                 args.iter()
1020                     .map(|a| context.snippet(a.span))
1021                     .collect::<Vec<_>>(),
1022             )
1023         }
1024         _ => None,
1025     })
1026 }
1027
1028 // Rewrite `extern crate foo;` WITHOUT attributes.
1029 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1030     assert!(is_extern_crate(item));
1031     let new_str = context.snippet(item.span);
1032     Some(if contains_comment(&new_str) {
1033         new_str
1034     } else {
1035         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1036         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1037     })
1038 }