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