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, visit};
  15 use syntax::attr::HasAttrs;
  16 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  17 use syntax::parse::ParseSess;
  18
  19 use expr::rewrite_literal;
  20 use spanned::Spanned;
  21 use codemap::{LineRangeUtils, SpanUtils};
  22 use comment::{contains_comment, recover_missing_comment_in_span, CodeCharKind, CommentCodeSlices,
  23               FindUncommented};
  24 use comment::rewrite_comment;
  25 use config::{BraceStyle, Config};
  26 use items::{format_impl, format_struct, format_struct_struct, format_trait,
  27             rewrite_associated_impl_type, rewrite_associated_type, rewrite_static,
  28             rewrite_type_alias};
  29 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  30             SeparatorTactic};
  31 use macros::{rewrite_macro, MacroPosition};
  32 use regex::Regex;
  33 use rewrite::{Rewrite, RewriteContext};
  34 use shape::{Indent, Shape};
  35 use utils::{self, contains_skip, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  36
  37 fn is_use_item(item: &ast::Item) -> bool {
  38     match item.node {
  39         ast::ItemKind::Use(_) => true,
  40         _ => false,
  41     }
  42 }
  43
  44 fn is_extern_crate(item: &ast::Item) -> bool {
  45     match item.node {
  46         ast::ItemKind::ExternCrate(..) => true,
  47         _ => false,
  48     }
  49 }
  50
  51 pub struct FmtVisitor<'a> {
  52     pub parse_session: &'a ParseSess,
  53     pub codemap: &'a CodeMap,
  54     pub buffer: StringBuffer,
  55     pub last_pos: BytePos,
  56     // FIXME: use an RAII util or closure for indenting
  57     pub block_indent: Indent,
  58     pub config: &'a Config,
  59     pub is_if_else_block: bool,
  60 }
  61
  62 impl<'a> FmtVisitor<'a> {
  63     pub fn shape(&self) -> Shape {
  64         Shape::indented(self.block_indent, self.config)
  65     }
  66
  67     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  68         debug!(
  69             "visit_stmt: {:?} {:?}",
  70             self.codemap.lookup_char_pos(stmt.span.lo()),
  71             self.codemap.lookup_char_pos(stmt.span.hi())
  72         );
  73
  74         match stmt.node {
  75             ast::StmtKind::Item(ref item) => {
  76                 self.visit_item(item);
  77             }
  78             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  79                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
  80                 self.push_rewrite(stmt.span(), rewrite)
  81             }
  82             ast::StmtKind::Mac(ref mac) => {
  83                 let (ref mac, _macro_style, ref attrs) = **mac;
  84                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
  85                     self.push_rewrite(stmt.span(), None);
  86                 } else {
  87                     self.visit_mac(mac, None, MacroPosition::Statement);
  88                 }
  89                 self.format_missing(stmt.span.hi());
  90             }
  91         }
  92     }
  93
  94     pub fn visit_block(&mut self, b: &ast::Block, inner_attrs: Option<&[ast::Attribute]>) {
  95         debug!(
  96             "visit_block: {:?} {:?}",
  97             self.codemap.lookup_char_pos(b.span.lo()),
  98             self.codemap.lookup_char_pos(b.span.hi())
  99         );
 100
 101         // Check if this block has braces.
 102         let snippet = self.snippet(b.span);
 103         let has_braces = snippet.starts_with('{') || snippet.starts_with("unsafe");
 104         let brace_compensation = if has_braces { BytePos(1) } else { BytePos(0) };
 105
 106         self.last_pos = self.last_pos + brace_compensation;
 107         self.block_indent = self.block_indent.block_indent(self.config);
 108         self.buffer.push_str("{");
 109
 110         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 111             if let Some(first_stmt) = b.stmts.first() {
 112                 let attr_lo = inner_attrs
 113                     .and_then(|attrs| {
 114                         inner_attributes(attrs).first().map(|attr| attr.span.lo())
 115                     })
 116                     .or_else(|| {
 117                         // Attributes for an item in a statement position
 118                         // do not belong to the statement. (rust-lang/rust#34459)
 119                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 120                             item.attrs.first()
 121                         } else {
 122                             first_stmt.attrs().first()
 123                         }.and_then(|attr| {
 124                             // Some stmts can have embedded attributes.
 125                             // e.g. `match { #![attr] ... }`
 126                             let attr_lo = attr.span.lo();
 127                             if attr_lo < first_stmt.span.lo() {
 128                                 Some(attr_lo)
 129                             } else {
 130                                 None
 131                             }
 132                         })
 133                     });
 134
 135                 let snippet = self.snippet(mk_sp(
 136                     self.last_pos,
 137                     attr_lo.unwrap_or(first_stmt.span.lo()),
 138                 ));
 139                 let len = CommentCodeSlices::new(&snippet).nth(0).and_then(
 140                     |(kind, _, s)| if kind == CodeCharKind::Normal {
 141                         s.rfind('\n')
 142                     } else {
 143                         None
 144                     },
 145                 );
 146                 if let Some(len) = len {
 147                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 148                 }
 149             }
 150         }
 151
 152         // Format inner attributes if available.
 153         if let Some(attrs) = inner_attrs {
 154             self.visit_attrs(attrs, ast::AttrStyle::Inner);
 155         }
 156
 157         self.walk_block_stmts(b);
 158
 159         if !b.stmts.is_empty() {
 160             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 161                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 162                     self.buffer.push_str(";");
 163                 }
 164             }
 165         }
 166
 167         let mut remove_len = BytePos(0);
 168         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 169             if let Some(stmt) = b.stmts.last() {
 170                 let snippet = self.snippet(mk_sp(
 171                     stmt.span.hi(),
 172                     source!(self, b.span).hi() - brace_compensation,
 173                 ));
 174                 let len = CommentCodeSlices::new(&snippet)
 175                     .last()
 176                     .and_then(|(kind, _, s)| {
 177                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 178                             Some(s.len())
 179                         } else {
 180                             None
 181                         }
 182                     });
 183                 if let Some(len) = len {
 184                     remove_len = BytePos::from_usize(len);
 185                 }
 186             }
 187         }
 188
 189         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 190         if unindent_comment {
 191             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 192             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 193             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 194         }
 195         // FIXME: we should compress any newlines here to just one
 196         if unindent_comment {
 197             self.block_indent = self.block_indent.block_unindent(self.config);
 198         }
 199         self.format_missing_with_indent(
 200             source!(self, b.span).hi() - brace_compensation - remove_len,
 201         );
 202         if unindent_comment {
 203             self.block_indent = self.block_indent.block_indent(self.config);
 204         }
 205         self.close_block(unindent_comment);
 206         self.last_pos = source!(self, b.span).hi();
 207     }
 208
 209     // FIXME: this is a terrible hack to indent the comments between the last
 210     // item in the block and the closing brace to the block's level.
 211     // The closing brace itself, however, should be indented at a shallower
 212     // level.
 213     fn close_block(&mut self, unindent_comment: bool) {
 214         let total_len = self.buffer.len;
 215         let chars_too_many = if unindent_comment {
 216             0
 217         } else if self.config.hard_tabs() {
 218             1
 219         } else {
 220             self.config.tab_spaces()
 221         };
 222         self.buffer.truncate(total_len - chars_too_many);
 223         self.buffer.push_str("}");
 224         self.block_indent = self.block_indent.block_unindent(self.config);
 225     }
 226
 227     // Note that this only gets called for function definitions. Required methods
 228     // on traits do not get handled here.
 229     fn visit_fn(
 230         &mut self,
 231         fk: visit::FnKind,
 232         fd: &ast::FnDecl,
 233         s: Span,
 234         _: ast::NodeId,
 235         defaultness: ast::Defaultness,
 236         inner_attrs: Option<&[ast::Attribute]>,
 237     ) {
 238         let indent = self.block_indent;
 239         let block;
 240         let rewrite = match fk {
 241             visit::FnKind::ItemFn(ident, generics, unsafety, constness, abi, vis, b) => {
 242                 block = b;
 243                 self.rewrite_fn(
 244                     indent,
 245                     ident,
 246                     fd,
 247                     generics,
 248                     unsafety,
 249                     constness.node,
 250                     defaultness,
 251                     abi,
 252                     vis,
 253                     mk_sp(s.lo(), b.span.lo()),
 254                     b,
 255                 )
 256             }
 257             visit::FnKind::Method(ident, sig, vis, b) => {
 258                 block = b;
 259                 self.rewrite_fn(
 260                     indent,
 261                     ident,
 262                     fd,
 263                     &sig.generics,
 264                     sig.unsafety,
 265                     sig.constness.node,
 266                     defaultness,
 267                     sig.abi,
 268                     vis.unwrap_or(&ast::Visibility::Inherited),
 269                     mk_sp(s.lo(), b.span.lo()),
 270                     b,
 271                 )
 272             }
 273             visit::FnKind::Closure(_) => unreachable!(),
 274         };
 275
 276         if let Some(fn_str) = rewrite {
 277             self.format_missing_with_indent(source!(self, s).lo());
 278             self.buffer.push_str(&fn_str);
 279             if let Some(c) = fn_str.chars().last() {
 280                 if c == '}' {
 281                     self.last_pos = source!(self, block.span).hi();
 282                     return;
 283                 }
 284             }
 285         } else {
 286             self.format_missing(source!(self, block.span).lo());
 287         }
 288
 289         self.last_pos = source!(self, block.span).lo();
 290         self.visit_block(block, inner_attrs)
 291     }
 292
 293     pub fn visit_item(&mut self, item: &ast::Item) {
 294         skip_out_of_file_lines_range_visitor!(self, item.span);
 295
 296         // This is where we bail out if there is a skip attribute. This is only
 297         // complex in the module case. It is complex because the module could be
 298         // in a separate file and there might be attributes in both files, but
 299         // the AST lumps them all together.
 300         let filterd_attrs;
 301         let mut attrs = &item.attrs;
 302         match item.node {
 303             ast::ItemKind::Mod(ref m) => {
 304                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 305                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 306                 if outer_file.name == inner_file.name {
 307                     // Module is inline, in this case we treat modules like any
 308                     // other item.
 309                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 310                         self.push_rewrite(item.span, None);
 311                         return;
 312                     }
 313                 } else if contains_skip(&item.attrs) {
 314                     // Module is not inline, but should be skipped.
 315                     return;
 316                 } else {
 317                     // Module is not inline and should not be skipped. We want
 318                     // to process only the attributes in the current file.
 319                     filterd_attrs = item.attrs
 320                         .iter()
 321                         .filter_map(|a| {
 322                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 323                             if attr_file.name == outer_file.name {
 324                                 Some(a.clone())
 325                             } else {
 326                                 None
 327                             }
 328                         })
 329                         .collect::<Vec<_>>();
 330                     // Assert because if we should skip it should be caught by
 331                     // the above case.
 332                     assert!(!self.visit_attrs(&filterd_attrs, ast::AttrStyle::Outer));
 333                     attrs = &filterd_attrs;
 334                 }
 335             }
 336             _ => if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 337                 self.push_rewrite(item.span, None);
 338                 return;
 339             },
 340         }
 341
 342         match item.node {
 343             ast::ItemKind::Use(ref vp) => self.format_import(item, vp),
 344             ast::ItemKind::Impl(..) => {
 345                 let snippet = self.snippet(item.span);
 346                 let where_span_end = snippet
 347                     .find_uncommented("{")
 348                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 349                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 350                 self.push_rewrite(item.span, rw);
 351             }
 352             ast::ItemKind::Trait(..) => {
 353                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 354                 self.push_rewrite(item.span, rw);
 355             }
 356             ast::ItemKind::ExternCrate(_) => {
 357                 let rw = rewrite_extern_crate(&self.get_context(), item);
 358                 self.push_rewrite(item.span, rw);
 359             }
 360             ast::ItemKind::Struct(ref def, ref generics) => {
 361                 let rewrite = format_struct(
 362                     &self.get_context(),
 363                     "struct ",
 364                     item.ident,
 365                     &item.vis,
 366                     def,
 367                     Some(generics),
 368                     item.span,
 369                     self.block_indent,
 370                     None,
 371                 ).map(|s| match *def {
 372                     ast::VariantData::Tuple(..) => s + ";",
 373                     _ => s,
 374                 });
 375                 self.push_rewrite(item.span, rewrite);
 376             }
 377             ast::ItemKind::Enum(ref def, ref generics) => {
 378                 self.format_missing_with_indent(source!(self, item.span).lo());
 379                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 380                 self.last_pos = source!(self, item.span).hi();
 381             }
 382             ast::ItemKind::Mod(ref module) => {
 383                 self.format_missing_with_indent(source!(self, item.span).lo());
 384                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 385             }
 386             ast::ItemKind::Mac(ref mac) => {
 387                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 388             }
 389             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 390                 self.format_missing_with_indent(source!(self, item.span).lo());
 391                 self.format_foreign_mod(foreign_mod, item.span);
 392             }
 393             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 394                 let rewrite = rewrite_static(
 395                     "static",
 396                     &item.vis,
 397                     item.ident,
 398                     ty,
 399                     mutability,
 400                     Some(expr),
 401                     self.block_indent,
 402                     item.span,
 403                     &self.get_context(),
 404                 );
 405                 self.push_rewrite(item.span, rewrite);
 406             }
 407             ast::ItemKind::Const(ref ty, ref expr) => {
 408                 let rewrite = rewrite_static(
 409                     "const",
 410                     &item.vis,
 411                     item.ident,
 412                     ty,
 413                     ast::Mutability::Immutable,
 414                     Some(expr),
 415                     self.block_indent,
 416                     item.span,
 417                     &self.get_context(),
 418                 );
 419                 self.push_rewrite(item.span, rewrite);
 420             }
 421             ast::ItemKind::DefaultImpl(..) => {
 422                 // FIXME(#78): format impl definitions.
 423             }
 424             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 425                 self.visit_fn(
 426                     visit::FnKind::ItemFn(
 427                         item.ident,
 428                         generics,
 429                         unsafety,
 430                         constness,
 431                         abi,
 432                         &item.vis,
 433                         body,
 434                     ),
 435                     decl,
 436                     item.span,
 437                     item.id,
 438                     ast::Defaultness::Final,
 439                     Some(&item.attrs),
 440                 )
 441             }
 442             ast::ItemKind::Ty(ref ty, ref generics) => {
 443                 let rewrite = rewrite_type_alias(
 444                     &self.get_context(),
 445                     self.block_indent,
 446                     item.ident,
 447                     ty,
 448                     generics,
 449                     &item.vis,
 450                     item.span,
 451                 );
 452                 self.push_rewrite(item.span, rewrite);
 453             }
 454             ast::ItemKind::Union(ref def, ref generics) => {
 455                 let rewrite = format_struct_struct(
 456                     &self.get_context(),
 457                     "union ",
 458                     item.ident,
 459                     &item.vis,
 460                     def.fields(),
 461                     Some(generics),
 462                     item.span,
 463                     self.block_indent,
 464                     None,
 465                 );
 466                 self.push_rewrite(item.span, rewrite);
 467             }
 468             ast::ItemKind::GlobalAsm(..) => {
 469                 let snippet = Some(self.snippet(item.span));
 470                 self.push_rewrite(item.span, snippet);
 471             }
 472             ast::ItemKind::MacroDef(..) => {
 473                 // FIXME(#1539): macros 2.0
 474                 let mac_snippet = Some(self.snippet(item.span));
 475                 self.push_rewrite(item.span, mac_snippet);
 476             }
 477         }
 478     }
 479
 480     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 481         skip_out_of_file_lines_range_visitor!(self, ti.span);
 482
 483         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 484             self.push_rewrite(ti.span, None);
 485             return;
 486         }
 487
 488         match ti.node {
 489             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 490                 let rewrite = rewrite_static(
 491                     "const",
 492                     &ast::Visibility::Inherited,
 493                     ti.ident,
 494                     ty,
 495                     ast::Mutability::Immutable,
 496                     expr_opt.as_ref(),
 497                     self.block_indent,
 498                     ti.span,
 499                     &self.get_context(),
 500                 );
 501                 self.push_rewrite(ti.span, rewrite);
 502             }
 503             ast::TraitItemKind::Method(ref sig, None) => {
 504                 let indent = self.block_indent;
 505                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 506                 self.push_rewrite(ti.span, rewrite);
 507             }
 508             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 509                 self.visit_fn(
 510                     visit::FnKind::Method(ti.ident, sig, None, body),
 511                     &sig.decl,
 512                     ti.span,
 513                     ti.id,
 514                     ast::Defaultness::Final,
 515                     Some(&ti.attrs),
 516                 );
 517             }
 518             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 519                 let rewrite = rewrite_associated_type(
 520                     ti.ident,
 521                     type_default.as_ref(),
 522                     Some(type_param_bounds),
 523                     &self.get_context(),
 524                     self.block_indent,
 525                 );
 526                 self.push_rewrite(ti.span, rewrite);
 527             }
 528             ast::TraitItemKind::Macro(ref mac) => {
 529                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 530             }
 531         }
 532     }
 533
 534     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 535         skip_out_of_file_lines_range_visitor!(self, ii.span);
 536
 537         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 538             self.push_rewrite(ii.span, None);
 539             return;
 540         }
 541
 542         match ii.node {
 543             ast::ImplItemKind::Method(ref sig, ref body) => {
 544                 self.visit_fn(
 545                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 546                     &sig.decl,
 547                     ii.span,
 548                     ii.id,
 549                     ii.defaultness,
 550                     Some(&ii.attrs),
 551                 );
 552             }
 553             ast::ImplItemKind::Const(ref ty, ref expr) => {
 554                 let rewrite = rewrite_static(
 555                     "const",
 556                     &ii.vis,
 557                     ii.ident,
 558                     ty,
 559                     ast::Mutability::Immutable,
 560                     Some(expr),
 561                     self.block_indent,
 562                     ii.span,
 563                     &self.get_context(),
 564                 );
 565                 self.push_rewrite(ii.span, rewrite);
 566             }
 567             ast::ImplItemKind::Type(ref ty) => {
 568                 let rewrite = rewrite_associated_impl_type(
 569                     ii.ident,
 570                     ii.defaultness,
 571                     Some(ty),
 572                     None,
 573                     &self.get_context(),
 574                     self.block_indent,
 575                 );
 576                 self.push_rewrite(ii.span, rewrite);
 577             }
 578             ast::ImplItemKind::Macro(ref mac) => {
 579                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 580             }
 581         }
 582     }
 583
 584     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 585         skip_out_of_file_lines_range_visitor!(self, mac.span);
 586
 587         // 1 = ;
 588         let shape = self.shape().sub_width(1).unwrap();
 589         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 590         self.push_rewrite(mac.span, rewrite);
 591     }
 592
 593     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 594         self.format_missing_with_indent(source!(self, span).lo());
 595         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 596         self.buffer.push_str(&result);
 597         self.last_pos = source!(self, span).hi();
 598     }
 599
 600     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 601         FmtVisitor {
 602             parse_session: parse_session,
 603             codemap: parse_session.codemap(),
 604             buffer: StringBuffer::new(),
 605             last_pos: BytePos(0),
 606             block_indent: Indent::empty(),
 607             config: config,
 608             is_if_else_block: false,
 609         }
 610     }
 611
 612     pub fn snippet(&self, span: Span) -> String {
 613         match self.codemap.span_to_snippet(span) {
 614             Ok(s) => s,
 615             Err(_) => {
 616                 println!(
 617                     "Couldn't make snippet for span {:?}->{:?}",
 618                     self.codemap.lookup_char_pos(span.lo()),
 619                     self.codemap.lookup_char_pos(span.hi())
 620                 );
 621                 "".to_owned()
 622             }
 623         }
 624     }
 625
 626     // Returns true if we should skip the following item.
 627     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 628         if contains_skip(attrs) {
 629             return true;
 630         }
 631
 632         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 633         if attrs.is_empty() {
 634             return false;
 635         }
 636
 637         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 638         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 639         self.push_rewrite(span, rewrite);
 640
 641         false
 642     }
 643
 644     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 645     where
 646         F: Fn(&ast::Item) -> bool,
 647     {
 648         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 649         let item_length = items_left
 650             .iter()
 651             .take_while(|ppi| {
 652                 is_item(&***ppi) && (!in_group || {
 653                     let current = self.codemap.lookup_line_range(ppi.span());
 654                     let in_same_group = current.lo < last.hi + 2;
 655                     last = current;
 656                     in_same_group
 657                 })
 658             })
 659             .count();
 660         let items = &items_left[..item_length];
 661
 662         let at_least_one_in_file_lines = items
 663             .iter()
 664             .any(|item| !out_of_file_lines_range!(self, item.span));
 665
 666         if at_least_one_in_file_lines {
 667             self.format_imports(items);
 668         } else {
 669             for item in items {
 670                 self.push_rewrite(item.span, None);
 671             }
 672         }
 673
 674         item_length
 675     }
 676
 677     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 678         while !items_left.is_empty() {
 679             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 680             // to be potentially reordered within `format_imports`. Otherwise, just format the
 681             // next item for output.
 682             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 683                 let used_items_len = self.reorder_items(
 684                     items_left,
 685                     &is_use_item,
 686                     self.config.reorder_imports_in_group(),
 687                 );
 688                 let (_, rest) = items_left.split_at(used_items_len);
 689                 items_left = rest;
 690             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 691                 let used_items_len = self.reorder_items(
 692                     items_left,
 693                     &is_extern_crate,
 694                     self.config.reorder_extern_crates_in_group(),
 695                 );
 696                 let (_, rest) = items_left.split_at(used_items_len);
 697                 items_left = rest;
 698             } else {
 699                 // `unwrap()` is safe here because we know `items_left`
 700                 // has elements from the loop condition
 701                 let (item, rest) = items_left.split_first().unwrap();
 702                 self.visit_item(item);
 703                 items_left = rest;
 704             }
 705         }
 706     }
 707
 708     fn walk_mod_items(&mut self, m: &ast::Mod) {
 709         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 710     }
 711
 712     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 713         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 714             match stmt.node {
 715                 ast::StmtKind::Item(ref item) => Some(&**item),
 716                 _ => None,
 717             }
 718         }
 719
 720         if stmts.is_empty() {
 721             return;
 722         }
 723
 724         // Extract leading `use ...;`.
 725         let items: Vec<_> = stmts
 726             .iter()
 727             .take_while(|stmt| to_stmt_item(stmt).is_some())
 728             .filter_map(|stmt| to_stmt_item(stmt))
 729             .take_while(|item| is_use_item(item))
 730             .collect();
 731
 732         if items.is_empty() {
 733             self.visit_stmt(&stmts[0]);
 734             self.walk_stmts(&stmts[1..]);
 735         } else {
 736             self.walk_items(&items);
 737             self.walk_stmts(&stmts[items.len()..]);
 738         }
 739     }
 740
 741     fn walk_block_stmts(&mut self, b: &ast::Block) {
 742         self.walk_stmts(&b.stmts)
 743     }
 744
 745     fn format_mod(
 746         &mut self,
 747         m: &ast::Mod,
 748         vis: &ast::Visibility,
 749         s: Span,
 750         ident: ast::Ident,
 751         attrs: &[ast::Attribute],
 752     ) {
 753         // Decide whether this is an inline mod or an external mod.
 754         let local_file_name = self.codemap.span_to_filename(s);
 755         let inner_span = source!(self, m.inner);
 756         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 757             && local_file_name == self.codemap.span_to_filename(inner_span);
 758
 759         self.buffer.push_str(&*utils::format_visibility(vis));
 760         self.buffer.push_str("mod ");
 761         self.buffer.push_str(&ident.to_string());
 762
 763         if is_internal {
 764             match self.config.item_brace_style() {
 765                 BraceStyle::AlwaysNextLine => self.buffer
 766                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 767                 _ => self.buffer.push_str(" {"),
 768             }
 769             // Hackery to account for the closing }.
 770             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 771             let body_snippet =
 772                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 773             let body_snippet = body_snippet.trim();
 774             if body_snippet.is_empty() {
 775                 self.buffer.push_str("}");
 776             } else {
 777                 self.last_pos = mod_lo;
 778                 self.block_indent = self.block_indent.block_indent(self.config);
 779                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 780                 self.walk_mod_items(m);
 781                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 782                 self.close_block(false);
 783             }
 784             self.last_pos = source!(self, m.inner).hi();
 785         } else {
 786             self.buffer.push_str(";");
 787             self.last_pos = source!(self, s).hi();
 788         }
 789     }
 790
 791     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 792         self.block_indent = Indent::empty();
 793         self.walk_mod_items(m);
 794         self.format_missing_with_indent(filemap.end_pos);
 795     }
 796
 797     pub fn get_context(&self) -> RewriteContext {
 798         RewriteContext {
 799             parse_session: self.parse_session,
 800             codemap: self.codemap,
 801             config: self.config,
 802             inside_macro: false,
 803             use_block: false,
 804             is_if_else_block: false,
 805             force_one_line_chain: false,
 806         }
 807     }
 808 }
 809
 810 impl Rewrite for ast::NestedMetaItem {
 811     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 812         match self.node {
 813             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 814             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 815         }
 816     }
 817 }
 818
 819 impl Rewrite for ast::MetaItem {
 820     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 821         Some(match self.node {
 822             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 823             ast::MetaItemKind::List(ref list) => {
 824                 let name = self.name.as_str();
 825                 // 3 = `#[` and `(`, 2 = `]` and `)`
 826                 let item_shape = try_opt!(
 827                     shape
 828                         .shrink_left(name.len() + 3)
 829                         .and_then(|s| s.sub_width(2))
 830                 );
 831                 let items = itemize_list(
 832                     context.codemap,
 833                     list.iter(),
 834                     ")",
 835                     |nested_meta_item| nested_meta_item.span.lo(),
 836                     |nested_meta_item| nested_meta_item.span.hi(),
 837                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 838                     self.span.lo(),
 839                     self.span.hi(),
 840                     false,
 841                 );
 842                 let item_vec = items.collect::<Vec<_>>();
 843                 let fmt = ListFormatting {
 844                     tactic: DefinitiveListTactic::Mixed,
 845                     separator: ",",
 846                     trailing_separator: SeparatorTactic::Never,
 847                     separator_place: SeparatorPlace::Back,
 848                     shape: item_shape,
 849                     ends_with_newline: false,
 850                     preserve_newline: false,
 851                     config: context.config,
 852                 };
 853                 format!("{}({})", name, try_opt!(write_list(&item_vec, &fmt)))
 854             }
 855             ast::MetaItemKind::NameValue(ref literal) => {
 856                 let name = self.name.as_str();
 857                 let value = context.snippet(literal.span);
 858                 if &*name == "doc" && contains_comment(&value) {
 859                     let doc_shape = Shape {
 860                         width: cmp::min(shape.width, context.config.comment_width())
 861                             .checked_sub(shape.indent.width())
 862                             .unwrap_or(0),
 863                         ..shape
 864                     };
 865                     try_opt!(rewrite_comment(&value, false, doc_shape, context.config))
 866                 } else {
 867                     format!("{} = {}", name, value)
 868                 }
 869             }
 870         })
 871     }
 872 }
 873
 874 impl Rewrite for ast::Attribute {
 875     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 876         try_opt!(self.meta())
 877             .rewrite(context, shape)
 878             .map(|rw| if self.is_sugared_doc {
 879                 rw
 880             } else {
 881                 let original = context.snippet(self.span);
 882                 let prefix = match self.style {
 883                     ast::AttrStyle::Inner => "#!",
 884                     ast::AttrStyle::Outer => "#",
 885                 };
 886                 if contains_comment(&original) {
 887                     original
 888                 } else {
 889                     format!("{}[{}]", prefix, rw)
 890                 }
 891             })
 892     }
 893 }
 894
 895 impl<'a> Rewrite for [ast::Attribute] {
 896     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 897         if self.is_empty() {
 898             return Some(String::new());
 899         }
 900         let mut result = String::with_capacity(128);
 901         let indent = shape.indent.to_string(context.config);
 902
 903         let mut derive_args = Vec::new();
 904
 905         let mut iter = self.iter().enumerate().peekable();
 906         let mut insert_new_line = true;
 907         let mut is_prev_sugared_doc = false;
 908         while let Some((i, a)) = iter.next() {
 909             let a_str = try_opt!(a.rewrite(context, shape));
 910
 911             // Write comments and blank lines between attributes.
 912             if i > 0 {
 913                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 914                 // This particular horror show is to preserve line breaks in between doc
 915                 // comments. An alternative would be to force such line breaks to start
 916                 // with the usual doc comment token.
 917                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc
 918                     || is_prev_sugared_doc
 919                 {
 920                     // Look at before and after comment and see if there are any empty lines.
 921                     let comment_begin = comment.chars().position(|c| c == '/');
 922                     let len = comment_begin.unwrap_or_else(|| comment.len());
 923                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 924                     let mla = if comment_begin.is_none() {
 925                         mlb
 926                     } else {
 927                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 928                         let len = comment_end.unwrap();
 929                         comment
 930                             .chars()
 931                             .rev()
 932                             .take(len)
 933                             .filter(|c| *c == '\n')
 934                             .count() > 1
 935                     };
 936                     (mlb, mla)
 937                 } else {
 938                     (false, false)
 939                 };
 940
 941                 let comment = try_opt!(recover_missing_comment_in_span(
 942                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 943                     shape.with_max_width(context.config),
 944                     context,
 945                     0,
 946                 ));
 947
 948                 if !comment.is_empty() {
 949                     if multi_line_before {
 950                         result.push('\n');
 951                     }
 952                     result.push_str(&comment);
 953                     result.push('\n');
 954                     if multi_line_after {
 955                         result.push('\n')
 956                     }
 957                 } else if insert_new_line {
 958                     result.push('\n');
 959                     if multi_line_after {
 960                         result.push('\n')
 961                     }
 962                 }
 963
 964                 if derive_args.is_empty() {
 965                     result.push_str(&indent);
 966                 }
 967
 968                 insert_new_line = true;
 969             }
 970
 971             // Write the attribute itself.
 972             if context.config.merge_derives() {
 973                 // If the attribute is `#[derive(...)]`, take the arguments.
 974                 if let Some(mut args) = get_derive_args(context, a) {
 975                     derive_args.append(&mut args);
 976                     match iter.peek() {
 977                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 978                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 979                         // If not, rewrite the merged derives.
 980                         _ => {
 981                             result.push_str(&try_opt!(format_derive(context, &derive_args, shape)));
 982                             derive_args.clear();
 983                         }
 984                     }
 985                 } else {
 986                     result.push_str(&a_str);
 987                 }
 988             } else {
 989                 result.push_str(&a_str);
 990             }
 991
 992             is_prev_sugared_doc = a.is_sugared_doc;
 993         }
 994         Some(result)
 995     }
 996 }
 997
 998 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 999 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
1000     let mut result = String::with_capacity(128);
1001     result.push_str("#[derive(");
1002     // 11 = `#[derive()]`
1003     let initial_budget = try_opt!(shape.width.checked_sub(11));
1004     let mut budget = initial_budget;
1005     let num = derive_args.len();
1006     for (i, a) in derive_args.iter().enumerate() {
1007         // 2 = `, ` or `)]`
1008         let width = a.len() + 2;
1009         if width > budget {
1010             if i > 0 {
1011                 // Remove trailing whitespace.
1012                 result.pop();
1013             }
1014             result.push('\n');
1015             // 9 = `#[derive(`
1016             result.push_str(&(shape.indent + 9).to_string(context.config));
1017             budget = initial_budget;
1018         } else {
1019             budget = budget.checked_sub(width).unwrap_or(0);
1020         }
1021         result.push_str(a);
1022         if i != num - 1 {
1023             result.push_str(", ")
1024         }
1025     }
1026     result.push_str(")]");
1027     Some(result)
1028 }
1029
1030 fn is_derive(attr: &ast::Attribute) -> bool {
1031     match attr.meta() {
1032         Some(meta_item) => match meta_item.node {
1033             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1034             _ => false,
1035         },
1036         _ => false,
1037     }
1038 }
1039
1040 /// Returns the arguments of `#[derive(...)]`.
1041 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1042     attr.meta().and_then(|meta_item| match meta_item.node {
1043         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1044             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1045             Some(
1046                 args.iter()
1047                     .map(|a| context.snippet(a.span))
1048                     .collect::<Vec<_>>(),
1049             )
1050         }
1051         _ => None,
1052     })
1053 }
1054
1055 // Rewrite `extern crate foo;` WITHOUT attributes.
1056 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1057     assert!(is_extern_crate(item));
1058     let new_str = context.snippet(item.span);
1059     Some(if contains_comment(&new_str) {
1060         new_str
1061     } else {
1062         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1063         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1064     })
1065 }