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 filterd_attrs;
 304         let mut attrs = &item.attrs;
 305         match item.node {
 306             ast::ItemKind::Mod(ref m) => {
 307                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 308                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 309                 if outer_file.name == inner_file.name {
 310                     // Module is inline, in this case we treat modules like any
 311                     // other item.
 312                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 313                         self.push_rewrite(item.span, None);
 314                         return;
 315                     }
 316                 } else if contains_skip(&item.attrs) {
 317                     // Module is not inline, but should be skipped.
 318                     return;
 319                 } else {
 320                     // Module is not inline and should not be skipped. We want
 321                     // to process only the attributes in the current file.
 322                     filterd_attrs = item.attrs
 323                         .iter()
 324                         .filter_map(|a| {
 325                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 326                             if attr_file.name == outer_file.name {
 327                                 Some(a.clone())
 328                             } else {
 329                                 None
 330                             }
 331                         })
 332                         .collect::<Vec<_>>();
 333                     // Assert because if we should skip it should be caught by
 334                     // the above case.
 335                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 336                     attrs = &filterd_attrs;
 337                 }
 338             }
 339             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 340                 self.push_rewrite(item.span, None);
 341                 return;
 342             },
 343         }
 344
 345         match item.node {
 346             ast::ItemKind::Use(ref vp) => self.format_import(&item, vp),
 347             ast::ItemKind::Impl(..) => {
 348                 let snippet = self.snippet(item.span);
 349                 let where_span_end = snippet
 350                     .find_uncommented("{")
 351                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 352                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 353                 self.push_rewrite(item.span, rw);
 354             }
 355             ast::ItemKind::Trait(..) => {
 356                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 357                 self.push_rewrite(item.span, rw);
 358             }
 359             ast::ItemKind::ExternCrate(_) => {
 360                 let rw = rewrite_extern_crate(&self.get_context(), item);
 361                 self.push_rewrite(item.span, rw);
 362             }
 363             ast::ItemKind::Struct(ref def, ref generics) => {
 364                 let rewrite = {
 365                     ::items::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                 };
 380                 self.push_rewrite(item.span, rewrite);
 381             }
 382             ast::ItemKind::Enum(ref def, ref generics) => {
 383                 self.format_missing_with_indent(source!(self, item.span).lo());
 384                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 385                 self.last_pos = source!(self, item.span).hi();
 386             }
 387             ast::ItemKind::Mod(ref module) => {
 388                 self.format_missing_with_indent(source!(self, item.span).lo());
 389                 self.format_mod(module, &item.vis, item.span, item.ident, &attrs);
 390             }
 391             ast::ItemKind::Mac(ref mac) => {
 392                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 393             }
 394             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 395                 self.format_missing_with_indent(source!(self, item.span).lo());
 396                 self.format_foreign_mod(foreign_mod, item.span);
 397             }
 398             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 399                 let rewrite = rewrite_static(
 400                     "static",
 401                     &item.vis,
 402                     item.ident,
 403                     ty,
 404                     mutability,
 405                     Some(expr),
 406                     self.block_indent,
 407                     item.span,
 408                     &self.get_context(),
 409                 );
 410                 self.push_rewrite(item.span, rewrite);
 411             }
 412             ast::ItemKind::Const(ref ty, ref expr) => {
 413                 let rewrite = rewrite_static(
 414                     "const",
 415                     &item.vis,
 416                     item.ident,
 417                     ty,
 418                     ast::Mutability::Immutable,
 419                     Some(expr),
 420                     self.block_indent,
 421                     item.span,
 422                     &self.get_context(),
 423                 );
 424                 self.push_rewrite(item.span, rewrite);
 425             }
 426             ast::ItemKind::DefaultImpl(..) => {
 427                 // FIXME(#78): format impl definitions.
 428             }
 429             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 430                 self.visit_fn(
 431                     visit::FnKind::ItemFn(
 432                         item.ident,
 433                         generics,
 434                         unsafety,
 435                         constness,
 436                         abi,
 437                         &item.vis,
 438                         body,
 439                     ),
 440                     decl,
 441                     item.span,
 442                     item.id,
 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::Union(ref def, ref generics) => {
 460                 let rewrite = ::items::format_struct_struct(
 461                     &self.get_context(),
 462                     "union ",
 463                     item.ident,
 464                     &item.vis,
 465                     def.fields(),
 466                     Some(generics),
 467                     item.span,
 468                     self.block_indent,
 469                     None,
 470                 );
 471                 self.push_rewrite(item.span, rewrite);
 472             }
 473             ast::ItemKind::GlobalAsm(..) => {
 474                 let snippet = Some(self.snippet(item.span));
 475                 self.push_rewrite(item.span, snippet);
 476             }
 477             ast::ItemKind::MacroDef(..) => {
 478                 // FIXME(#1539): macros 2.0
 479                 let mac_snippet = Some(self.snippet(item.span));
 480                 self.push_rewrite(item.span, mac_snippet);
 481             }
 482         }
 483     }
 484
 485     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 486         skip_out_of_file_lines_range_visitor!(self, ti.span);
 487
 488         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 489             self.push_rewrite(ti.span, None);
 490             return;
 491         }
 492
 493         match ti.node {
 494             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 495                 let rewrite = rewrite_static(
 496                     "const",
 497                     &ast::Visibility::Inherited,
 498                     ti.ident,
 499                     ty,
 500                     ast::Mutability::Immutable,
 501                     expr_opt.as_ref(),
 502                     self.block_indent,
 503                     ti.span,
 504                     &self.get_context(),
 505                 );
 506                 self.push_rewrite(ti.span, rewrite);
 507             }
 508             ast::TraitItemKind::Method(ref sig, None) => {
 509                 let indent = self.block_indent;
 510                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 511                 self.push_rewrite(ti.span, rewrite);
 512             }
 513             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 514                 self.visit_fn(
 515                     visit::FnKind::Method(ti.ident, sig, None, body),
 516                     &sig.decl,
 517                     ti.span,
 518                     ti.id,
 519                     ast::Defaultness::Final,
 520                     Some(&ti.attrs),
 521                 );
 522             }
 523             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 524                 let rewrite = rewrite_associated_type(
 525                     ti.ident,
 526                     type_default.as_ref(),
 527                     Some(type_param_bounds),
 528                     &self.get_context(),
 529                     self.block_indent,
 530                 );
 531                 self.push_rewrite(ti.span, rewrite);
 532             }
 533             ast::TraitItemKind::Macro(ref mac) => {
 534                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 535             }
 536         }
 537     }
 538
 539     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 540         skip_out_of_file_lines_range_visitor!(self, ii.span);
 541
 542         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 543             self.push_rewrite(ii.span, None);
 544             return;
 545         }
 546
 547         match ii.node {
 548             ast::ImplItemKind::Method(ref sig, ref body) => {
 549                 self.visit_fn(
 550                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 551                     &sig.decl,
 552                     ii.span,
 553                     ii.id,
 554                     ii.defaultness,
 555                     Some(&ii.attrs),
 556                 );
 557             }
 558             ast::ImplItemKind::Const(ref ty, ref expr) => {
 559                 let rewrite = rewrite_static(
 560                     "const",
 561                     &ii.vis,
 562                     ii.ident,
 563                     ty,
 564                     ast::Mutability::Immutable,
 565                     Some(expr),
 566                     self.block_indent,
 567                     ii.span,
 568                     &self.get_context(),
 569                 );
 570                 self.push_rewrite(ii.span, rewrite);
 571             }
 572             ast::ImplItemKind::Type(ref ty) => {
 573                 let rewrite = rewrite_associated_impl_type(
 574                     ii.ident,
 575                     ii.defaultness,
 576                     Some(ty),
 577                     None,
 578                     &self.get_context(),
 579                     self.block_indent,
 580                 );
 581                 self.push_rewrite(ii.span, rewrite);
 582             }
 583             ast::ImplItemKind::Macro(ref mac) => {
 584                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 585             }
 586         }
 587     }
 588
 589     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 590         skip_out_of_file_lines_range_visitor!(self, mac.span);
 591
 592         // 1 = ;
 593         let shape = self.shape().sub_width(1).unwrap();
 594         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 595         self.push_rewrite(mac.span, rewrite);
 596     }
 597
 598     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 599         self.format_missing_with_indent(source!(self, span).lo());
 600         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 601         self.buffer.push_str(&result);
 602         self.last_pos = source!(self, span).hi();
 603     }
 604
 605     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 606         FmtVisitor {
 607             parse_session: parse_session,
 608             codemap: parse_session.codemap(),
 609             buffer: StringBuffer::new(),
 610             last_pos: BytePos(0),
 611             block_indent: Indent::empty(),
 612             config: config,
 613             is_if_else_block: false,
 614         }
 615     }
 616
 617     pub fn snippet(&self, span: Span) -> String {
 618         match self.codemap.span_to_snippet(span) {
 619             Ok(s) => s,
 620             Err(_) => {
 621                 println!(
 622                     "Couldn't make snippet for span {:?}->{:?}",
 623                     self.codemap.lookup_char_pos(span.lo()),
 624                     self.codemap.lookup_char_pos(span.hi())
 625                 );
 626                 "".to_owned()
 627             }
 628         }
 629     }
 630
 631     // Returns true if we should skip the following item.
 632     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 633         if contains_skip(attrs) {
 634             return true;
 635         }
 636
 637         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 638         if attrs.is_empty() {
 639             return false;
 640         }
 641
 642         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 643         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 644         self.push_rewrite(span, rewrite);
 645
 646         false
 647     }
 648
 649     fn reorder_items<F>(
 650         &mut self,
 651         items_left: &[ptr::P<ast::Item>],
 652         is_item: &F,
 653         in_group: bool,
 654     ) -> usize
 655     where
 656         F: Fn(&ast::Item) -> bool,
 657     {
 658         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 659         let item_length = items_left
 660             .iter()
 661             .take_while(|ppi| {
 662                 is_item(&***ppi) && (!in_group || {
 663                     let current = self.codemap.lookup_line_range(ppi.span());
 664                     let in_same_group = current.lo < last.hi + 2;
 665                     last = current;
 666                     in_same_group
 667                 })
 668             })
 669             .count();
 670         let items = &items_left[..item_length];
 671
 672         let at_least_one_in_file_lines = items
 673             .iter()
 674             .any(|item| !out_of_file_lines_range!(self, item.span));
 675
 676         if at_least_one_in_file_lines {
 677             self.format_imports(items);
 678         } else {
 679             for item in items {
 680                 self.push_rewrite(item.span, None);
 681             }
 682         }
 683
 684         item_length
 685     }
 686
 687     fn walk_mod_items(&mut self, m: &ast::Mod) {
 688         let mut items_left: &[ptr::P<ast::Item>] = &m.items;
 689         while !items_left.is_empty() {
 690             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 691             // to be potentially reordered within `format_imports`. Otherwise, just format the
 692             // next item for output.
 693             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 694                 let used_items_len = self.reorder_items(
 695                     items_left,
 696                     &is_use_item,
 697                     self.config.reorder_imports_in_group(),
 698                 );
 699                 let (_, rest) = items_left.split_at(used_items_len);
 700                 items_left = rest;
 701             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 702                 let used_items_len = self.reorder_items(
 703                     items_left,
 704                     &is_extern_crate,
 705                     self.config.reorder_extern_crates_in_group(),
 706                 );
 707                 let (_, rest) = items_left.split_at(used_items_len);
 708                 items_left = rest;
 709             } else {
 710                 // `unwrap()` is safe here because we know `items_left`
 711                 // has elements from the loop condition
 712                 let (item, rest) = items_left.split_first().unwrap();
 713                 self.visit_item(item);
 714                 items_left = rest;
 715             }
 716         }
 717     }
 718
 719     fn format_mod(
 720         &mut self,
 721         m: &ast::Mod,
 722         vis: &ast::Visibility,
 723         s: Span,
 724         ident: ast::Ident,
 725         attrs: &[ast::Attribute],
 726     ) {
 727         // Decide whether this is an inline mod or an external mod.
 728         let local_file_name = self.codemap.span_to_filename(s);
 729         let inner_span = source!(self, m.inner);
 730         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0) &&
 731             local_file_name == self.codemap.span_to_filename(inner_span);
 732
 733         self.buffer.push_str(&*utils::format_visibility(vis));
 734         self.buffer.push_str("mod ");
 735         self.buffer.push_str(&ident.to_string());
 736
 737         if is_internal {
 738             match self.config.item_brace_style() {
 739                 BraceStyle::AlwaysNextLine => self.buffer
 740                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 741                 _ => self.buffer.push_str(" {"),
 742             }
 743             // Hackery to account for the closing }.
 744             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 745             let body_snippet =
 746                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 747             let body_snippet = body_snippet.trim();
 748             if body_snippet.is_empty() {
 749                 self.buffer.push_str("}");
 750             } else {
 751                 self.last_pos = mod_lo;
 752                 self.block_indent = self.block_indent.block_indent(self.config);
 753                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 754                 self.walk_mod_items(m);
 755                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 756                 self.close_block(false);
 757             }
 758             self.last_pos = source!(self, m.inner).hi();
 759         } else {
 760             self.buffer.push_str(";");
 761             self.last_pos = source!(self, s).hi();
 762         }
 763     }
 764
 765     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 766         self.block_indent = Indent::empty();
 767         self.walk_mod_items(m);
 768         self.format_missing_with_indent(filemap.end_pos);
 769     }
 770
 771     pub fn get_context(&self) -> RewriteContext {
 772         RewriteContext {
 773             parse_session: self.parse_session,
 774             codemap: self.codemap,
 775             config: self.config,
 776             inside_macro: false,
 777             use_block: false,
 778             is_if_else_block: false,
 779             force_one_line_chain: false,
 780         }
 781     }
 782 }
 783
 784 impl Rewrite for ast::NestedMetaItem {
 785     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 786         match self.node {
 787             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 788             ast::NestedMetaItemKind::Literal(..) => Some(context.snippet(self.span)),
 789         }
 790     }
 791 }
 792
 793 impl Rewrite for ast::MetaItem {
 794     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 795         Some(match self.node {
 796             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 797             ast::MetaItemKind::List(ref list) => {
 798                 let name = self.name.as_str();
 799                 // 3 = `#[` and `(`, 2 = `]` and `)`
 800                 let item_shape = try_opt!(
 801                     shape
 802                         .shrink_left(name.len() + 3)
 803                         .and_then(|s| s.sub_width(2))
 804                 );
 805                 let items = itemize_list(
 806                     context.codemap,
 807                     list.iter(),
 808                     ")",
 809                     |nested_meta_item| nested_meta_item.span.lo(),
 810                     |nested_meta_item| nested_meta_item.span.hi(),
 811                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 812                     self.span.lo(),
 813                     self.span.hi(),
 814                     false,
 815                 );
 816                 let item_vec = items.collect::<Vec<_>>();
 817                 let fmt = ListFormatting {
 818                     tactic: DefinitiveListTactic::Mixed,
 819                     separator: ",",
 820                     trailing_separator: SeparatorTactic::Never,
 821                     separator_place: SeparatorPlace::Back,
 822                     shape: item_shape,
 823                     ends_with_newline: false,
 824                     preserve_newline: false,
 825                     config: context.config,
 826                 };
 827                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 828             }
 829             ast::MetaItemKind::NameValue(ref literal) => {
 830                 let name = self.name.as_str();
 831                 let value = context.snippet(literal.span);
 832                 if &*name == "doc" && contains_comment(&value) {
 833                     let doc_shape = Shape {
 834                         width: cmp::min(shape.width, context.config.comment_width())
 835                             .checked_sub(shape.indent.width())
 836                             .unwrap_or(0),
 837                         ..shape
 838                     };
 839                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 840                 } else {
 841                     format!("{} = {}", name, value)
 842                 }
 843             }
 844         })
 845     }
 846 }
 847
 848 impl Rewrite for ast::Attribute {
 849     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 850         try_opt!(self.meta())
 851             .rewrite(context, shape)
 852             .map(|rw| if self.is_sugared_doc {
 853                 rw
 854             } else {
 855                 let original = context.snippet(self.span);
 856                 let prefix = match self.style {
 857                     ast::AttrStyle::Inner => "#!",
 858                     ast::AttrStyle::Outer => "#",
 859                 };
 860                 if contains_comment(&original) {
 861                     original
 862                 } else {
 863                     format!("{}[{}]", prefix, rw)
 864                 }
 865             })
 866     }
 867 }
 868
 869 impl<'a> Rewrite for [ast::Attribute] {
 870     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 871         if self.is_empty() {
 872             return Some(String::new());
 873         }
 874         let mut result = String::with_capacity(128);
 875         let indent = shape.indent.to_string(context.config);
 876
 877         let mut derive_args = Vec::new();
 878
 879         let mut iter = self.iter().enumerate().peekable();
 880         let mut insert_new_line = true;
 881         let mut is_prev_sugared_doc = false;
 882         while let Some((i, a)) = iter.next() {
 883             let a_str = try_opt!(a.rewrite(context, shape));
 884
 885             // Write comments and blank lines between attributes.
 886             if i > 0 {
 887                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 888                 // This particular horror show is to preserve line breaks in between doc
 889                 // comments. An alternative would be to force such line breaks to start
 890                 // with the usual doc comment token.
 891                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc ||
 892                     is_prev_sugared_doc
 893                 {
 894                     // Look at before and after comment and see if there are any empty lines.
 895                     let comment_begin = comment.chars().position(|c| c == '/');
 896                     let len = comment_begin.unwrap_or_else(|| comment.len());
 897                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 898                     let mla = if comment_begin.is_none() {
 899                         mlb
 900                     } else {
 901                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 902                         let len = comment_end.unwrap();
 903                         comment
 904                             .chars()
 905                             .rev()
 906                             .take(len)
 907                             .filter(|c| *c == '\n')
 908                             .count() > 1
 909                     };
 910                     (mlb, mla)
 911                 } else {
 912                     (false, false)
 913                 };
 914
 915                 let comment = try_opt!(recover_missing_comment_in_span(
 916                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 917                     shape.with_max_width(context.config),
 918                     context,
 919                     0,
 920                 ));
 921
 922                 if !comment.is_empty() {
 923                     if multi_line_before {
 924                         result.push('\n');
 925                     }
 926                     result.push_str(&comment);
 927                     result.push('\n');
 928                     if multi_line_after {
 929                         result.push('\n')
 930                     }
 931                 } else if insert_new_line {
 932                     result.push('\n');
 933                     if multi_line_after {
 934                         result.push('\n')
 935                     }
 936                 }
 937
 938                 if derive_args.is_empty() {
 939                     result.push_str(&indent);
 940                 }
 941
 942                 insert_new_line = true;
 943             }
 944
 945             // Write the attribute itself.
 946             if context.config.merge_derives() {
 947                 // If the attribute is `#[derive(...)]`, take the arguments.
 948                 if let Some(mut args) = get_derive_args(context, a) {
 949                     derive_args.append(&mut args);
 950                     match iter.peek() {
 951                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 952                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 953                         // If not, rewrite the merged derives.
 954                         _ => {
 955                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 956                             derive_args.clear();
 957                         }
 958                     }
 959                 } else {
 960                     result.push_str(&a_str);
 961                 }
 962             } else {
 963                 result.push_str(&a_str);
 964             }
 965
 966             is_prev_sugared_doc = a.is_sugared_doc;
 967         }
 968         Some(result)
 969     }
 970 }
 971
 972 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 973 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 974     let mut result = String::with_capacity(128);
 975     result.push_str("#[derive(");
 976     // 11 = `#[derive()]`
 977     let initial_budget = try_opt!(shape.width.checked_sub(11));
 978     let mut budget = initial_budget;
 979     let num = derive_args.len();
 980     for (i, a) in derive_args.iter().enumerate() {
 981         // 2 = `, ` or `)]`
 982         let width = a.len() + 2;
 983         if width > budget {
 984             if i > 0 {
 985                 // Remove trailing whitespace.
 986                 result.pop();
 987             }
 988             result.push('\n');
 989             // 9 = `#[derive(`
 990             result.push_str(&(shape.indent + 9).to_string(context.config));
 991             budget = initial_budget;
 992         } else {
 993             budget = budget.checked_sub(width).unwrap_or(0);
 994         }
 995         result.push_str(a);
 996         if i != num - 1 {
 997             result.push_str(", ")
 998         }
 999     }
1000     result.push_str(")]");
1001     Some(result)
1002 }
1003
1004 fn is_derive(attr: &ast::Attribute) -> bool {
1005     match attr.meta() {
1006         Some(meta_item) => match meta_item.node {
1007             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1008             _ => false,
1009         },
1010         _ => false,
1011     }
1012 }
1013
1014 /// Returns the arguments of `#[derive(...)]`.
1015 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1016     attr.meta().and_then(|meta_item| match meta_item.node {
1017         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1018             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1019             Some(
1020                 args.iter()
1021                     .map(|a| context.snippet(a.span))
1022                     .collect::<Vec<_>>(),
1023             )
1024         }
1025         _ => None,
1026     })
1027 }
1028
1029 // Rewrite `extern crate foo;` WITHOUT attributes.
1030 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1031     assert!(is_extern_crate(item));
1032     let new_str = context.snippet(item.span);
1033     Some(if contains_comment(&new_str) {
1034         new_str
1035     } else {
1036         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1037         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1038     })
1039 }