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_trait, rewrite_associated_impl_type, rewrite_associated_type,
  26             rewrite_static, rewrite_type_alias};
  27 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  28             SeparatorTactic};
  29 use macros::{rewrite_macro, MacroPosition};
  30 use regex::Regex;
  31 use rewrite::{Rewrite, RewriteContext};
  32 use utils::{self, contains_skip, inner_attributes, mk_sp};
  33
  34 fn is_use_item(item: &ast::Item) -> bool {
  35     match item.node {
  36         ast::ItemKind::Use(_) => true,
  37         _ => false,
  38     }
  39 }
  40
  41 fn is_extern_crate(item: &ast::Item) -> bool {
  42     match item.node {
  43         ast::ItemKind::ExternCrate(..) => true,
  44         _ => false,
  45     }
  46 }
  47
  48 pub struct FmtVisitor<'a> {
  49     pub parse_session: &'a ParseSess,
  50     pub codemap: &'a CodeMap,
  51     pub buffer: StringBuffer,
  52     pub last_pos: BytePos,
  53     // FIXME: use an RAII util or closure for indenting
  54     pub block_indent: Indent,
  55     pub config: &'a Config,
  56     pub is_if_else_block: bool,
  57 }
  58
  59 impl<'a> FmtVisitor<'a> {
  60     pub fn shape(&self) -> Shape {
  61         Shape::indented(self.block_indent, self.config)
  62     }
  63
  64     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  65         debug!(
  66             "visit_stmt: {:?} {:?}",
  67             self.codemap.lookup_char_pos(stmt.span.lo()),
  68             self.codemap.lookup_char_pos(stmt.span.hi())
  69         );
  70
  71         match stmt.node {
  72             ast::StmtKind::Item(ref item) => {
  73                 self.visit_item(item);
  74             }
  75             ast::StmtKind::Local(..) => {
  76                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  77                 self.push_rewrite(stmt.span(), rewrite);
  78             }
  79             ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  80                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  81                 self.push_rewrite(stmt.span(), rewrite)
  82             }
  83             ast::StmtKind::Mac(ref mac) => {
  84                 let (ref mac, _macro_style, ref attrs) = **mac;
  85                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  86                     self.push_rewrite(stmt.span(), None);
  87                 } else {
  88                     self.visit_mac(mac, None, MacroPosition::Statement);
  89                 }
  90                 self.format_missing(stmt.span.hi());
  91             }
  92         }
  93     }
  94
  95     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
  96         debug!(
  97             "visit_block: {:?} {:?}",
  98             self.codemap.lookup_char_pos(b.span.lo()),
  99             self.codemap.lookup_char_pos(b.span.hi())
 100         );
 101
 102         // Check if this block has braces.
 103         let snippet = self.snippet(b.span);
 104         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 105         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 106
 107         self.last_pos = self.last_pos + brace_compensation;
 108         self.block_indent = self.block_indent.block_indent(self.config);
 109         self.buffer.push_str("{");
 110
 111         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 112             if let Some(first_stmt) = b.stmts.first() {
 113                 let attr_lo = inner_attrs
 114                     .and_then(|attrs| {
 115                         inner_attributes(attrs).first().map(|attr| attr.span.lo())
 116                     })
 117                     .or_else(|| {
 118                         // Attributes for an item in a statement position
 119                         // do not belong to the statement. (rust-lang/rust#34459)
 120                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 121                             item.attrs.first()
 122                         } else {
 123                             first_stmt.attrs().first()
 124                         }.and_then(|attr| {
 125                             // Some stmts can have embedded attributes.
 126                             // e.g. `match { #![attr] ... }`
 127                             let attr_lo = attr.span.lo();
 128                             if attr_lo < first_stmt.span.lo() {
 129                                 Some(attr_lo)
 130                             } else {
 131                                 None
 132                             }
 133                         })
 134                     });
 135
 136                 let snippet = self.snippet(mk_sp(
 137                     self.last_pos,
 138                     attr_lo.unwrap_or(first_stmt.span.lo()),
 139                 ));
 140                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 141                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 142                         s.rfind('\n')
 143                     } else {
 144                         None
 145                     },
 146                 );
 147                 if let Some(len) = len {
 148                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 149                 }
 150             }
 151         }
 152
 153         // Format inner attributes if available.
 154         if let Some(attrs) = inner_attrs {
 155             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 156         }
 157
 158         for stmt in &b.stmts {
 159             self.visit_stmt(stmt)
 160         }
 161
 162         if !b.stmts.is_empty() {
 163             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 164                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 165                     self.buffer.push_str(";");
 166                 }
 167             }
 168         }
 169
 170         let mut remove_len = BytePos(0);
 171         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 172             if let Some(stmt) = b.stmts.last() {
 173                 let snippet = self.snippet(mk_sp(
 174                     stmt.span.hi(),
 175                     source!(self, b.span).hi() - brace_compensation,
 176                 ));
 177                 let len = CommentCodeSlices::new(&snippet)
 178                     .last()
 179                     .and_then(|(kind, _, s)| {
 180                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 181                             Some(s.len())
 182                         } else {
 183                             None
 184                         }
 185                     });
 186                 if let Some(len) = len {
 187                     remove_len = BytePos::from_usize(len);
 188                 }
 189             }
 190         }
 191
 192         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 193         if unindent_comment {
 194             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 195             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 196             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 197         }
 198         // FIXME: we should compress any newlines here to just one
 199         if unindent_comment {
 200             self.block_indent = self.block_indent.block_unindent(self.config);
 201         }
 202         self.format_missing_with_indent(
 203             source!(self, b.span).hi() - brace_compensation - remove_len,
 204         );
 205         if unindent_comment {
 206             self.block_indent = self.block_indent.block_indent(self.config);
 207         }
 208         self.close_block(unindent_comment);
 209         self.last_pos = source!(self, b.span).hi();
 210     }
 211
 212     // FIXME: this is a terrible hack to indent the comments between the last
 213     // item in the block and the closing brace to the block's level.
 214     // The closing brace itself, however, should be indented at a shallower
 215     // level.
 216     fn close_block(&mut self, unindent_comment: bool) {
 217         let total_len = self.buffer.len;
 218         let chars_too_many = if unindent_comment {
 219             0
 220         } else if self.config.hard_tabs() {
 221             1
 222         } else {
 223             self.config.tab_spaces()
 224         };
 225         self.buffer.truncate(total_len - chars_too_many);
 226         self.buffer.push_str("}");
 227         self.block_indent = self.block_indent.block_unindent(self.config);
 228     }
 229
 230     // Note that this only gets called for function definitions. Required methods
 231     // on traits do not get handled here.
 232     fn visit_fn(
 233         &mut self,
 234         fk: visit::FnKind,
 235         fd: &ast::FnDecl,
 236         s: Span,
 237         _: ast::NodeId,
 238         defaultness: ast::Defaultness,
 239         inner_attrs: Option<&[ast::Attribute]>,
 240     ) {
 241         let indent = self.block_indent;
 242         let block;
 243         let rewrite = match fk {
 244             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 245                 block = b;
 246                 self.rewrite_fn(
 247                     indent,
 248                     ident,
 249                     fd,
 250                     generics,
 251                     unsafety,
 252                     constness.node,
 253                     defaultness,
 254                     abi,
 255                     vis,
 256                     mk_sp(s.lo(), b.span.lo()),
 257                     b,
 258                 )
 259             }
 260             visit::FnKind::Method(ident, sig, vis, b) => {
 261                 block = b;
 262                 self.rewrite_fn(
 263                     indent,
 264                     ident,
 265                     fd,
 266                     &sig.generics,
 267                     sig.unsafety,
 268                     sig.constness.node,
 269                     defaultness,
 270                     sig.abi,
 271                     vis.unwrap_or(&ast::Visibility::Inherited),
 272                     mk_sp(s.lo(), b.span.lo()),
 273                     b,
 274                 )
 275             }
 276             visit::FnKind::Closure(_) => unreachable!(),
 277         };
 278
 279         if let Some(fn_str) = rewrite {
 280             self.format_missing_with_indent(source!(self, s).lo());
 281             self.buffer.push_str(&fn_str);
 282             if let Some(c) = fn_str.chars().last() {
 283                 if c == '}' {
 284                     self.last_pos = source!(self, block.span).hi();
 285                     return;
 286                 }
 287             }
 288         } else {
 289             self.format_missing(source!(self, block.span).lo());
 290         }
 291
 292         self.last_pos = source!(self, block.span).lo();
 293         self.visit_block(block, inner_attrs)
 294     }
 295
 296     pub fn visit_item(&mut self, item: &ast::Item) {
 297         skip_out_of_file_lines_range_visitor!(self, item.span);
 298
 299         // This is where we bail out if there is a skip attribute. This is only
 300         // complex in the module case. It is complex because the module could be
 301         // in a separate file and there might be attributes in both files, but
 302         // the AST lumps them all together.
 303         let mut attrs = item.attrs.clone();
 304         match item.node {
 305             ast::ItemKind::Mod(ref m) => {
 306                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 307                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 308                 if outer_file.name == inner_file.name {
 309                     // Module is inline, in this case we treat modules like any
 310                     // other item.
 311                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 312                         self.push_rewrite(item.span, None);
 313                         return;
 314                     }
 315                 } else if contains_skip(&item.attrs) {
 316                     // Module is not inline, but should be skipped.
 317                     return;
 318                 } else {
 319                     // Module is not inline and should not be skipped. We want
 320                     // to process only the attributes in the current file.
 321                     let filterd_attrs = item.attrs
 322                         .iter()
 323                         .filter_map(|a| {
 324                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 325                             if attr_file.name == outer_file.name {
 326                                 Some(a.clone())
 327                             } else {
 328                                 None
 329                             }
 330                         })
 331                         .collect::<Vec<_>>();
 332                     // Assert because if we should skip it should be caught by
 333                     // the above case.
 334                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 335                     attrs = filterd_attrs;
 336                 }
 337             }
 338             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 339                 self.push_rewrite(item.span, None);
 340                 return;
 341             },
 342         }
 343
 344         match item.node {
 345             ast::ItemKind::Use(ref vp) => {
 346                 self.format_import(&item.vis, vp, item.span, &item.attrs);
 347             }
 348             ast::ItemKind::Impl(..) => {
 349                 self.format_missing_with_indent(source!(self, item.span).lo());
 350                 let snippet = self.snippet(item.span);
 351                 let where_span_end = snippet
 352                     .find_uncommented("{")
 353                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 354                 if let Some(impl_str) =
 355                     format_impl(&self.get_context(), item, self.block_indent, where_span_end)
 356                 {
 357                     self.buffer.push_str(&impl_str);
 358                     self.last_pos = source!(self, item.span).hi();
 359                 }
 360             }
 361             ast::ItemKind::Trait(..) => {
 362                 self.format_missing_with_indent(item.span.lo());
 363                 if let Some(trait_str) = format_trait(&self.get_context(), item, self.block_indent)
 364                 {
 365                     self.buffer.push_str(&trait_str);
 366                     self.last_pos = source!(self, item.span).hi();
 367                 }
 368             }
 369             ast::ItemKind::ExternCrate(_) => {
 370                 self.format_missing_with_indent(source!(self, item.span).lo());
 371                 let new_str = self.snippet(item.span);
 372                 if contains_comment(&new_str) {
 373                     self.buffer.push_str(&new_str)
 374                 } else {
 375                     let no_whitespace =
 376                         &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
 377                     self.buffer
 378                         .push_str(&Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"));
 379                 }
 380                 self.last_pos = source!(self, item.span).hi();
 381             }
 382             ast::ItemKind::Struct(ref def, ref generics) => {
 383                 let rewrite = {
 384                     let indent = self.block_indent;
 385                     let context = self.get_context();
 386                     ::items::format_struct(
 387                         &context,
 388                         "struct ",
 389                         item.ident,
 390                         &item.vis,
 391                         def,
 392                         Some(generics),
 393                         item.span,
 394                         indent,
 395                         None,
 396                     ).map(|s| match *def {
 397                         ast::VariantData::Tuple(..) => s + ";",
 398                         _ => s,
 399                     })
 400                 };
 401                 self.push_rewrite(item.span, rewrite);
 402             }
 403             ast::ItemKind::Enum(ref def, ref generics) => {
 404                 self.format_missing_with_indent(source!(self, item.span).lo());
 405                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 406                 self.last_pos = source!(self, item.span).hi();
 407             }
 408             ast::ItemKind::Mod(ref module) => {
 409                 self.format_missing_with_indent(source!(self, item.span).lo());
 410                 self.format_mod(module, &item.vis, item.span, item.ident, &attrs);
 411             }
 412             ast::ItemKind::Mac(ref mac) => {
 413                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 414             }
 415             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 416                 self.format_missing_with_indent(source!(self, item.span).lo());
 417                 self.format_foreign_mod(foreign_mod, item.span);
 418             }
 419             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 420                 let rewrite = rewrite_static(
 421                     "static",
 422                     &item.vis,
 423                     item.ident,
 424                     ty,
 425                     mutability,
 426                     Some(expr),
 427                     self.block_indent,
 428                     item.span,
 429                     &self.get_context(),
 430                 );
 431                 self.push_rewrite(item.span, rewrite);
 432             }
 433             ast::ItemKind::Const(ref ty, ref expr) => {
 434                 let rewrite = rewrite_static(
 435                     "const",
 436                     &item.vis,
 437                     item.ident,
 438                     ty,
 439                     ast::Mutability::Immutable,
 440                     Some(expr),
 441                     self.block_indent,
 442                     item.span,
 443                     &self.get_context(),
 444                 );
 445                 self.push_rewrite(item.span, rewrite);
 446             }
 447             ast::ItemKind::DefaultImpl(..) => {
 448                 // FIXME(#78): format impl definitions.
 449             }
 450             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 451                 self.visit_fn(
 452                     visit::FnKind::ItemFn(
 453                         item.ident,
 454                         generics,
 455                         unsafety,
 456                         constness,
 457                         abi,
 458                         &item.vis,
 459                         body,
 460                     ),
 461                     decl,
 462                     item.span,
 463                     item.id,
 464                     ast::Defaultness::Final,
 465                     Some(&item.attrs),
 466                 )
 467             }
 468             ast::ItemKind::Ty(ref ty, ref generics) => {
 469                 let rewrite = rewrite_type_alias(
 470                     &self.get_context(),
 471                     self.block_indent,
 472                     item.ident,
 473                     ty,
 474                     generics,
 475                     &item.vis,
 476                     item.span,
 477                 );
 478                 self.push_rewrite(item.span, rewrite);
 479             }
 480             ast::ItemKind::Union(ref def, ref generics) => {
 481                 let rewrite = ::items::format_struct_struct(
 482                     &self.get_context(),
 483                     "union ",
 484                     item.ident,
 485                     &item.vis,
 486                     def.fields(),
 487                     Some(generics),
 488                     item.span,
 489                     self.block_indent,
 490                     None,
 491                 );
 492                 self.push_rewrite(item.span, rewrite);
 493             }
 494             ast::ItemKind::GlobalAsm(..) => {
 495                 let snippet = Some(self.snippet(item.span));
 496                 self.push_rewrite(item.span, snippet);
 497             }
 498             ast::ItemKind::MacroDef(..) => {
 499                 // FIXME(#1539): macros 2.0
 500                 let mac_snippet = Some(self.snippet(item.span));
 501                 self.push_rewrite(item.span, mac_snippet);
 502             }
 503         }
 504     }
 505
 506     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 507         skip_out_of_file_lines_range_visitor!(self, ti.span);
 508
 509         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 510             self.push_rewrite(ti.span, None);
 511             return;
 512         }
 513
 514         match ti.node {
 515             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 516                 let rewrite = rewrite_static(
 517                     "const",
 518                     &ast::Visibility::Inherited,
 519                     ti.ident,
 520                     ty,
 521                     ast::Mutability::Immutable,
 522                     expr_opt.as_ref(),
 523                     self.block_indent,
 524                     ti.span,
 525                     &self.get_context(),
 526                 );
 527                 self.push_rewrite(ti.span, rewrite);
 528             }
 529             ast::TraitItemKind::Method(ref sig, None) => {
 530                 let indent = self.block_indent;
 531                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 532                 self.push_rewrite(ti.span, rewrite);
 533             }
 534             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 535                 self.visit_fn(
 536                     visit::FnKind::Method(ti.ident, sig, None, body),
 537                     &sig.decl,
 538                     ti.span,
 539                     ti.id,
 540                     ast::Defaultness::Final,
 541                     Some(&ti.attrs),
 542                 );
 543             }
 544             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 545                 let rewrite = rewrite_associated_type(
 546                     ti.ident,
 547                     type_default.as_ref(),
 548                     Some(type_param_bounds),
 549                     &self.get_context(),
 550                     self.block_indent,
 551                 );
 552                 self.push_rewrite(ti.span, rewrite);
 553             }
 554             ast::TraitItemKind::Macro(ref mac) => {
 555                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 556             }
 557         }
 558     }
 559
 560     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 561         skip_out_of_file_lines_range_visitor!(self, ii.span);
 562
 563         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 564             self.push_rewrite(ii.span, None);
 565             return;
 566         }
 567
 568         match ii.node {
 569             ast::ImplItemKind::Method(ref sig, ref body) => {
 570                 self.visit_fn(
 571                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 572                     &sig.decl,
 573                     ii.span,
 574                     ii.id,
 575                     ii.defaultness,
 576                     Some(&ii.attrs),
 577                 );
 578             }
 579             ast::ImplItemKind::Const(ref ty, ref expr) => {
 580                 let rewrite = rewrite_static(
 581                     "const",
 582                     &ii.vis,
 583                     ii.ident,
 584                     ty,
 585                     ast::Mutability::Immutable,
 586                     Some(expr),
 587                     self.block_indent,
 588                     ii.span,
 589                     &self.get_context(),
 590                 );
 591                 self.push_rewrite(ii.span, rewrite);
 592             }
 593             ast::ImplItemKind::Type(ref ty) => {
 594                 let rewrite = rewrite_associated_impl_type(
 595                     ii.ident,
 596                     ii.defaultness,
 597                     Some(ty),
 598                     None,
 599                     &self.get_context(),
 600                     self.block_indent,
 601                 );
 602                 self.push_rewrite(ii.span, rewrite);
 603             }
 604             ast::ImplItemKind::Macro(ref mac) => {
 605                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 606             }
 607         }
 608     }
 609
 610     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 611         skip_out_of_file_lines_range_visitor!(self, mac.span);
 612
 613         // 1 = ;
 614         let shape = self.shape().sub_width(1).unwrap();
 615         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 616         self.push_rewrite(mac.span, rewrite);
 617     }
 618
 619     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 620         self.format_missing_with_indent(source!(self, span).lo());
 621         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 622         self.buffer.push_str(&result);
 623         self.last_pos = source!(self, span).hi();
 624     }
 625
 626     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 627         FmtVisitor {
 628             parse_session: parse_session,
 629             codemap: parse_session.codemap(),
 630             buffer: StringBuffer::new(),
 631             last_pos: BytePos(0),
 632             block_indent: Indent::empty(),
 633             config: config,
 634             is_if_else_block: false,
 635         }
 636     }
 637
 638     pub fn snippet(&self, span: Span) -> String {
 639         match self.codemap.span_to_snippet(span) {
 640             Ok(s) => s,
 641             Err(_) => {
 642                 println!(
 643                     "Couldn't make snippet for span {:?}->{:?}",
 644                     self.codemap.lookup_char_pos(span.lo()),
 645                     self.codemap.lookup_char_pos(span.hi())
 646                 );
 647                 "".to_owned()
 648             }
 649         }
 650     }
 651
 652     // Returns true if we should skip the following item.
 653     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 654         if contains_skip(attrs) {
 655             return true;
 656         }
 657
 658         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 659         if attrs.is_empty() {
 660             return false;
 661         }
 662
 663         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 664         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 665         self.push_rewrite(span, rewrite);
 666
 667         false
 668     }
 669
 670     fn reorder_items<F>(
 671         &mut self,
 672         items_left: &[ptr::P<ast::Item>],
 673         is_item: &F,
 674         in_group: bool,
 675     ) -> usize
 676     where
 677         F: Fn(&ast::Item) -> bool,
 678     {
 679         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 680         let item_length = items_left
 681             .iter()
 682             .take_while(|ppi| {
 683                 is_item(&***ppi) && (!in_group || {
 684                     let current = self.codemap.lookup_line_range(ppi.span());
 685                     let in_same_group = current.lo < last.hi + 2;
 686                     last = current;
 687                     in_same_group
 688                 })
 689             })
 690             .count();
 691         let items = &items_left[..item_length];
 692
 693         let at_least_one_in_file_lines = items
 694             .iter()
 695             .any(|item| !out_of_file_lines_range!(self, item.span));
 696
 697         if at_least_one_in_file_lines {
 698             self.format_imports(items);
 699         } else {
 700             for item in items {
 701                 self.push_rewrite(item.span, None);
 702             }
 703         }
 704
 705         item_length
 706     }
 707
 708     fn walk_mod_items(&mut self, m: &ast::Mod) {
 709         let mut items_left: &[ptr::P<ast::Item>] = &m.items;
 710         while !items_left.is_empty() {
 711             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 712             // to be potentially reordered within `format_imports`. Otherwise, just format the
 713             // next item for output.
 714             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 715                 let used_items_len = self.reorder_items(
 716                     items_left,
 717                     &is_use_item,
 718                     self.config.reorder_imports_in_group(),
 719                 );
 720                 let (_, rest) = items_left.split_at(used_items_len);
 721                 items_left = rest;
 722             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 723                 let used_items_len = self.reorder_items(
 724                     items_left,
 725                     &is_extern_crate,
 726                     self.config.reorder_extern_crates_in_group(),
 727                 );
 728                 let (_, rest) = items_left.split_at(used_items_len);
 729                 items_left = rest;
 730             } else {
 731                 // `unwrap()` is safe here because we know `items_left`
 732                 // has elements from the loop condition
 733                 let (item, rest) = items_left.split_first().unwrap();
 734                 self.visit_item(item);
 735                 items_left = rest;
 736             }
 737         }
 738     }
 739
 740     fn format_mod(
 741         &mut self,
 742         m: &ast::Mod,
 743         vis: &ast::Visibility,
 744         s: Span,
 745         ident: ast::Ident,
 746         attrs: &[ast::Attribute],
 747     ) {
 748         // Decide whether this is an inline mod or an external mod.
 749         let local_file_name = self.codemap.span_to_filename(s);
 750         let inner_span = source!(self, m.inner);
 751         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0) &&
 752             local_file_name == self.codemap.span_to_filename(inner_span);
 753
 754         self.buffer.push_str(&*utils::format_visibility(vis));
 755         self.buffer.push_str("mod ");
 756         self.buffer.push_str(&ident.to_string());
 757
 758         if is_internal {
 759             match self.config.item_brace_style() {
 760                 BraceStyle::AlwaysNextLine => self.buffer
 761                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 762                 _ => self.buffer.push_str(" {"),
 763             }
 764             // Hackery to account for the closing }.
 765             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 766             let body_snippet =
 767                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 768             let body_snippet = body_snippet.trim();
 769             if body_snippet.is_empty() {
 770                 self.buffer.push_str("}");
 771             } else {
 772                 self.last_pos = mod_lo;
 773                 self.block_indent = self.block_indent.block_indent(self.config);
 774                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 775                 self.walk_mod_items(m);
 776                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 777                 self.close_block(false);
 778             }
 779             self.last_pos = source!(self, m.inner).hi();
 780         } else {
 781             self.buffer.push_str(";");
 782             self.last_pos = source!(self, s).hi();
 783         }
 784     }
 785
 786     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 787         self.block_indent = Indent::empty();
 788         self.walk_mod_items(m);
 789         self.format_missing_with_indent(filemap.end_pos);
 790     }
 791
 792     pub fn get_context(&self) -> RewriteContext {
 793         RewriteContext {
 794             parse_session: self.parse_session,
 795             codemap: self.codemap,
 796             config: self.config,
 797             inside_macro: false,
 798             use_block: false,
 799             is_if_else_block: false,
 800             force_one_line_chain: false,
 801         }
 802     }
 803 }
 804
 805 impl Rewrite for ast::NestedMetaItem {
 806     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 807         match self.node {
 808             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 809             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 810         }
 811     }
 812 }
 813
 814 impl Rewrite for ast::MetaItem {
 815     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 816         Some(match self.node {
 817             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 818             ast::MetaItemKind::List(ref list) => {
 819                 let name = self.name.as_str();
 820                 // 3 = `#[` and `(`, 2 = `]` and `)`
 821                 let item_shape = try_opt!(
 822                     shape
 823                         .shrink_left(name.len() + 3)
 824                         .and_then(|s| s.sub_width(2))
 825                 );
 826                 let items = itemize_list(
 827                     context.codemap,
 828                     list.iter(),
 829                     ")",
 830                     |nested_meta_item| nested_meta_item.span.lo(),
 831                     |nested_meta_item| nested_meta_item.span.hi(),
 832                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 833                     self.span.lo(),
 834                     self.span.hi(),
 835                     false,
 836                 );
 837                 let item_vec = items.collect::<Vec<_>>();
 838                 let fmt = ListFormatting {
 839                     tactic: DefinitiveListTactic::Mixed,
 840                     separator: ",",
 841                     trailing_separator: SeparatorTactic::Never,
 842                     separator_place: SeparatorPlace::Back,
 843                     shape: item_shape,
 844                     ends_with_newline: false,
 845                     preserve_newline: false,
 846                     config: context.config,
 847                 };
 848                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 849             }
 850             ast::MetaItemKind::NameValue(ref literal) => {
 851                 let name = self.name.as_str();
 852                 let value = context.snippet(literal.span);
 853                 if &*name == "doc" && contains_comment(&value) {
 854                     let doc_shape = Shape {
 855                         width: cmp::min(shape.width, context.config.comment_width())
 856                             .checked_sub(shape.indent.width())
 857                             .unwrap_or(0),
 858                         ..shape
 859                     };
 860                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 861                 } else {
 862                     format!("{} = {}", name, value)
 863                 }
 864             }
 865         })
 866     }
 867 }
 868
 869 impl Rewrite for ast::Attribute {
 870     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 871         try_opt!(self.meta())
 872             .rewrite(context, shape)
 873             .map(|rw| if self.is_sugared_doc {
 874                 rw
 875             } else {
 876                 let original = context.snippet(self.span);
 877                 let prefix = match self.style {
 878                     ast::AttrStyle::Inner => "#!",
 879                     ast::AttrStyle::Outer => "#",
 880                 };
 881                 if contains_comment(&original) {
 882                     original
 883                 } else {
 884                     format!("{}[{}]", prefix, rw)
 885                 }
 886             })
 887     }
 888 }
 889
 890 impl<'a> Rewrite for [ast::Attribute] {
 891     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 892         if self.is_empty() {
 893             return Some(String::new());
 894         }
 895         let mut result = String::with_capacity(128);
 896         let indent = shape.indent.to_string(context.config);
 897
 898         let mut derive_args = Vec::new();
 899
 900         let mut iter = self.iter().enumerate().peekable();
 901         let mut insert_new_line = true;
 902         let mut is_prev_sugared_doc = false;
 903         while let Some((i, a)) = iter.next() {
 904             let a_str = try_opt!(a.rewrite(context, shape));
 905
 906             // Write comments and blank lines between attributes.
 907             if i > 0 {
 908                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 909                 // This particular horror show is to preserve line breaks in between doc
 910                 // comments. An alternative would be to force such line breaks to start
 911                 // with the usual doc comment token.
 912                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc ||
 913                     is_prev_sugared_doc
 914                 {
 915                     // Look at before and after comment and see if there are any empty lines.
 916                     let comment_begin = comment.chars().position(|c| c == '/');
 917                     let len = comment_begin.unwrap_or_else(|| comment.len());
 918                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 919                     let mla = if comment_begin.is_none() {
 920                         mlb
 921                     } else {
 922                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 923                         let len = comment_end.unwrap();
 924                         comment
 925                             .chars()
 926                             .rev()
 927                             .take(len)
 928                             .filter(|c| *c == '\n')
 929                             .count() > 1
 930                     };
 931                     (mlb, mla)
 932                 } else {
 933                     (false, false)
 934                 };
 935
 936                 let comment = try_opt!(recover_missing_comment_in_span(
 937                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 938                     shape.with_max_width(context.config),
 939                     context,
 940                     0,
 941                 ));
 942
 943                 if !comment.is_empty() {
 944                     if multi_line_before {
 945                         result.push('\n');
 946                     }
 947                     result.push_str(&comment);
 948                     result.push('\n');
 949                     if multi_line_after {
 950                         result.push('\n')
 951                     }
 952                 } else if insert_new_line {
 953                     result.push('\n');
 954                     if multi_line_after {
 955                         result.push('\n')
 956                     }
 957                 }
 958
 959                 if derive_args.is_empty() {
 960                     result.push_str(&indent);
 961                 }
 962
 963                 insert_new_line = true;
 964             }
 965
 966             // Write the attribute itself.
 967             if context.config.merge_derives() {
 968                 // If the attribute is `#[derive(...)]`, take the arguments.
 969                 if let Some(mut args) = get_derive_args(context, a) {
 970                     derive_args.append(&mut args);
 971                     match iter.peek() {
 972                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 973                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 974                         // If not, rewrite the merged derives.
 975                         _ => {
 976                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 977                             derive_args.clear();
 978                         }
 979                     }
 980                 } else {
 981                     result.push_str(&a_str);
 982                 }
 983             } else {
 984                 result.push_str(&a_str);
 985             }
 986
 987             is_prev_sugared_doc = a.is_sugared_doc;
 988         }
 989         Some(result)
 990     }
 991 }
 992
 993 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 994 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 995     let mut result = String::with_capacity(128);
 996     result.push_str("#[derive(");
 997     // 11 = `#[derive()]`
 998     let initial_budget = try_opt!(shape.width.checked_sub(11));
 999     let mut budget = initial_budget;
1000     let num = derive_args.len();
1001     for (i, a) in derive_args.iter().enumerate() {
1002         // 2 = `, ` or `)]`
1003         let width = a.len() + 2;
1004         if width > budget {
1005             if i > 0 {
1006                 // Remove trailing whitespace.
1007                 result.pop();
1008             }
1009             result.push('\n');
1010             // 9 = `#[derive(`
1011             result.push_str(&(shape.indent + 9).to_string(context.config));
1012             budget = initial_budget;
1013         } else {
1014             budget = budget.checked_sub(width).unwrap_or(0);
1015         }
1016         result.push_str(a);
1017         if i != num - 1 {
1018             result.push_str(", ")
1019         }
1020     }
1021     result.push_str(")]");
1022     Some(result)
1023 }
1024
1025 fn is_derive(attr: &ast::Attribute) -> bool {
1026     match attr.meta() {
1027         Some(meta_item) => match meta_item.node {
1028             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1029             _ => false,
1030         },
1031         _ => false,
1032     }
1033 }
1034
1035 /// Returns the arguments of `#[derive(...)]`.
1036 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1037     attr.meta().and_then(|meta_item| match meta_item.node {
1038         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1039             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1040             Some(
1041                 args.iter()
1042                     .map(|a| context.snippet(a.span))
1043                     .collect::<Vec<_>>(),
1044             )
1045         }
1046         _ => None,
1047     })
1048 }