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)
 140                     .nth(0)
 141                     .and_then(|(kind, _, s)| {
 142                         if kind == CodeCharKind::Normal {
 143                             s.rfind('\n')
 144                         } else {
 145                             None
 146                         }
 147                     });
 148                 if let Some(len) = len {
 149                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 150                 }
 151             }
 152         }
 153
 154         // Format inner attributes if available.
 155         let skip_rewrite = if let Some(attrs) = inner_attrs {
 156             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 157         } else {
 158             false
 159         };
 160
 161         if skip_rewrite {
 162             self.push_rewrite(b.span, None);
 163             self.close_block(false);
 164             self.last_pos = source!(self, b.span).hi();
 165             return;
 166         }
 167
 168         self.walk_block_stmts(b);
 169
 170         if !b.stmts.is_empty() {
 171             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 172                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 173                     self.buffer.push_str(";");
 174                 }
 175             }
 176         }
 177
 178         let mut remove_len = BytePos(0);
 179         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 180             if let Some(stmt) = b.stmts.last() {
 181                 let snippet = self.snippet(mk_sp(
 182                     stmt.span.hi(),
 183                     source!(self, b.span).hi() - brace_compensation,
 184                 ));
 185                 let len = CommentCodeSlices::new(&snippet)
 186                     .last()
 187                     .and_then(|(kind, _, s)| {
 188                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 189                             Some(s.len())
 190                         } else {
 191                             None
 192                         }
 193                     });
 194                 if let Some(len) = len {
 195                     remove_len = BytePos::from_usize(len);
 196                 }
 197             }
 198         }
 199
 200         let mut unindent_comment = self.is_if_else_block && !b.stmts.is_empty();
 201         if unindent_comment {
 202             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 203             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 204             unindent_comment = snippet.contains("//") || snippet.contains("/*");
 205         }
 206         // FIXME: we should compress any newlines here to just one
 207         if unindent_comment {
 208             self.block_indent = self.block_indent.block_unindent(self.config);
 209         }
 210         self.format_missing_with_indent(
 211             source!(self, b.span).hi() - brace_compensation - remove_len,
 212         );
 213         if unindent_comment {
 214             self.block_indent = self.block_indent.block_indent(self.config);
 215         }
 216         self.close_block(unindent_comment);
 217         self.last_pos = source!(self, b.span).hi();
 218     }
 219
 220     // FIXME: this is a terrible hack to indent the comments between the last
 221     // item in the block and the closing brace to the block's level.
 222     // The closing brace itself, however, should be indented at a shallower
 223     // level.
 224     fn close_block(&mut self, unindent_comment: bool) {
 225         let total_len = self.buffer.len;
 226         let chars_too_many = if unindent_comment {
 227             0
 228         } else if self.config.hard_tabs() {
 229             1
 230         } else {
 231             self.config.tab_spaces()
 232         };
 233         self.buffer.truncate(total_len - chars_too_many);
 234         self.buffer.push_str("}");
 235         self.block_indent = self.block_indent.block_unindent(self.config);
 236     }
 237
 238     // Note that this only gets called for function definitions. Required methods
 239     // on traits do not get handled here.
 240     fn visit_fn(
 241         &mut self,
 242         fk: visit::FnKind,
 243         generics: &ast::Generics,
 244         fd: &ast::FnDecl,
 245         s: Span,
 246         _: ast::NodeId,
 247         defaultness: ast::Defaultness,
 248         inner_attrs: Option<&[ast::Attribute]>,
 249     ) {
 250         let indent = self.block_indent;
 251         let block;
 252         let rewrite = match fk {
 253             visit::FnKind::ItemFn(ident, _, _, _, _, b) => {
 254                 block = b;
 255                 self.rewrite_fn(
 256                     indent,
 257                     ident,
 258                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 259                     mk_sp(s.lo(), b.span.lo()),
 260                     b,
 261                 )
 262             }
 263             visit::FnKind::Method(ident, _, _, b) => {
 264                 block = b;
 265                 self.rewrite_fn(
 266                     indent,
 267                     ident,
 268                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 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 filtered_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                     filtered_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(&filtered_attrs, ast::AttrStyle::Outer));
 333                     attrs = &filtered_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::AutoImpl(..) => {
 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(item.ident, unsafety, constness, abi, &item.vis, body),
 427                     generics,
 428                     decl,
 429                     item.span,
 430                     item.id,
 431                     ast::Defaultness::Final,
 432                     Some(&item.attrs),
 433                 )
 434             }
 435             ast::ItemKind::Ty(ref ty, ref generics) => {
 436                 let rewrite = rewrite_type_alias(
 437                     &self.get_context(),
 438                     self.block_indent,
 439                     item.ident,
 440                     ty,
 441                     generics,
 442                     &item.vis,
 443                     item.span,
 444                 );
 445                 self.push_rewrite(item.span, rewrite);
 446             }
 447             ast::ItemKind::Union(ref def, ref generics) => {
 448                 let rewrite = format_struct_struct(
 449                     &self.get_context(),
 450                     "union ",
 451                     item.ident,
 452                     &item.vis,
 453                     def.fields(),
 454                     Some(generics),
 455                     item.span,
 456                     self.block_indent,
 457                     None,
 458                 );
 459                 self.push_rewrite(item.span, rewrite);
 460             }
 461             ast::ItemKind::GlobalAsm(..) => {
 462                 let snippet = Some(self.snippet(item.span));
 463                 self.push_rewrite(item.span, snippet);
 464             }
 465             ast::ItemKind::MacroDef(..) => {
 466                 // FIXME(#1539): macros 2.0
 467                 let mac_snippet = Some(remove_trailing_white_spaces(&self.snippet(item.span)));
 468                 self.push_rewrite(item.span, mac_snippet);
 469             }
 470         }
 471     }
 472
 473     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 474         skip_out_of_file_lines_range_visitor!(self, ti.span);
 475
 476         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 477             self.push_rewrite(ti.span, None);
 478             return;
 479         }
 480
 481         match ti.node {
 482             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 483                 let rewrite = rewrite_static(
 484                     "const",
 485                     &ast::Visibility::Inherited,
 486                     ti.ident,
 487                     ty,
 488                     ast::Mutability::Immutable,
 489                     expr_opt.as_ref(),
 490                     self.block_indent,
 491                     ti.span,
 492                     &self.get_context(),
 493                 );
 494                 self.push_rewrite(ti.span, rewrite);
 495             }
 496             ast::TraitItemKind::Method(ref sig, None) => {
 497                 let indent = self.block_indent;
 498                 let rewrite =
 499                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 500                 self.push_rewrite(ti.span, rewrite);
 501             }
 502             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 503                 self.visit_fn(
 504                     visit::FnKind::Method(ti.ident, sig, None, body),
 505                     &ti.generics,
 506                     &sig.decl,
 507                     ti.span,
 508                     ti.id,
 509                     ast::Defaultness::Final,
 510                     Some(&ti.attrs),
 511                 );
 512             }
 513             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 514                 let rewrite = rewrite_associated_type(
 515                     ti.ident,
 516                     type_default.as_ref(),
 517                     Some(type_param_bounds),
 518                     &self.get_context(),
 519                     self.block_indent,
 520                 );
 521                 self.push_rewrite(ti.span, rewrite);
 522             }
 523             ast::TraitItemKind::Macro(ref mac) => {
 524                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 525             }
 526         }
 527     }
 528
 529     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 530         skip_out_of_file_lines_range_visitor!(self, ii.span);
 531
 532         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 533             self.push_rewrite(ii.span, None);
 534             return;
 535         }
 536
 537         match ii.node {
 538             ast::ImplItemKind::Method(ref sig, ref body) => {
 539                 self.visit_fn(
 540                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 541                     &ii.generics,
 542                     &sig.decl,
 543                     ii.span,
 544                     ii.id,
 545                     ii.defaultness,
 546                     Some(&ii.attrs),
 547                 );
 548             }
 549             ast::ImplItemKind::Const(ref ty, ref expr) => {
 550                 let rewrite = rewrite_static(
 551                     "const",
 552                     &ii.vis,
 553                     ii.ident,
 554                     ty,
 555                     ast::Mutability::Immutable,
 556                     Some(expr),
 557                     self.block_indent,
 558                     ii.span,
 559                     &self.get_context(),
 560                 );
 561                 self.push_rewrite(ii.span, rewrite);
 562             }
 563             ast::ImplItemKind::Type(ref ty) => {
 564                 let rewrite = rewrite_associated_impl_type(
 565                     ii.ident,
 566                     ii.defaultness,
 567                     Some(ty),
 568                     None,
 569                     &self.get_context(),
 570                     self.block_indent,
 571                 );
 572                 self.push_rewrite(ii.span, rewrite);
 573             }
 574             ast::ImplItemKind::Macro(ref mac) => {
 575                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 576             }
 577         }
 578     }
 579
 580     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 581         skip_out_of_file_lines_range_visitor!(self, mac.span);
 582
 583         // 1 = ;
 584         let shape = self.shape().sub_width(1).unwrap();
 585         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 586         self.push_rewrite(mac.span, rewrite);
 587     }
 588
 589     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 590         self.format_missing_with_indent(source!(self, span).lo());
 591         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 592         self.buffer.push_str(&result);
 593         self.last_pos = source!(self, span).hi();
 594     }
 595
 596     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 597         FmtVisitor {
 598             parse_session: parse_session,
 599             codemap: parse_session.codemap(),
 600             buffer: StringBuffer::new(),
 601             last_pos: BytePos(0),
 602             block_indent: Indent::empty(),
 603             config: config,
 604             is_if_else_block: false,
 605         }
 606     }
 607
 608     pub fn snippet(&self, span: Span) -> String {
 609         match self.codemap.span_to_snippet(span) {
 610             Ok(s) => s,
 611             Err(_) => {
 612                 eprintln!(
 613                     "Couldn't make snippet for span {:?}->{:?}",
 614                     self.codemap.lookup_char_pos(span.lo()),
 615                     self.codemap.lookup_char_pos(span.hi())
 616                 );
 617                 "".to_owned()
 618             }
 619         }
 620     }
 621
 622     // Returns true if we should skip the following item.
 623     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 624         if contains_skip(attrs) {
 625             return true;
 626         }
 627
 628         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 629         if attrs.is_empty() {
 630             return false;
 631         }
 632
 633         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 634         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 635         self.push_rewrite(span, rewrite);
 636
 637         false
 638     }
 639
 640     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 641     where
 642         F: Fn(&ast::Item) -> bool,
 643     {
 644         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 645         let item_length = items_left
 646             .iter()
 647             .take_while(|ppi| {
 648                 is_item(&***ppi) && (!in_group || {
 649                     let current = self.codemap.lookup_line_range(ppi.span());
 650                     let in_same_group = current.lo < last.hi + 2;
 651                     last = current;
 652                     in_same_group
 653                 })
 654             })
 655             .count();
 656         let items = &items_left[..item_length];
 657
 658         let at_least_one_in_file_lines = items
 659             .iter()
 660             .any(|item| !out_of_file_lines_range!(self, item.span));
 661
 662         if at_least_one_in_file_lines {
 663             self.format_imports(items);
 664         } else {
 665             for item in items {
 666                 self.push_rewrite(item.span, None);
 667             }
 668         }
 669
 670         item_length
 671     }
 672
 673     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 674         while !items_left.is_empty() {
 675             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 676             // to be potentially reordered within `format_imports`. Otherwise, just format the
 677             // next item for output.
 678             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 679                 let used_items_len = self.reorder_items(
 680                     items_left,
 681                     &is_use_item,
 682                     self.config.reorder_imports_in_group(),
 683                 );
 684                 let (_, rest) = items_left.split_at(used_items_len);
 685                 items_left = rest;
 686             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 687                 let used_items_len = self.reorder_items(
 688                     items_left,
 689                     &is_extern_crate,
 690                     self.config.reorder_extern_crates_in_group(),
 691                 );
 692                 let (_, rest) = items_left.split_at(used_items_len);
 693                 items_left = rest;
 694             } else {
 695                 // `unwrap()` is safe here because we know `items_left`
 696                 // has elements from the loop condition
 697                 let (item, rest) = items_left.split_first().unwrap();
 698                 self.visit_item(item);
 699                 items_left = rest;
 700             }
 701         }
 702     }
 703
 704     fn walk_mod_items(&mut self, m: &ast::Mod) {
 705         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 706     }
 707
 708     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 709         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 710             match stmt.node {
 711                 ast::StmtKind::Item(ref item) => Some(&**item),
 712                 _ => None,
 713             }
 714         }
 715
 716         if stmts.is_empty() {
 717             return;
 718         }
 719
 720         // Extract leading `use ...;`.
 721         let items: Vec<_> = stmts
 722             .iter()
 723             .take_while(|stmt| to_stmt_item(stmt).is_some())
 724             .filter_map(|stmt| to_stmt_item(stmt))
 725             .take_while(|item| is_use_item(item))
 726             .collect();
 727
 728         if items.is_empty() {
 729             self.visit_stmt(&stmts[0]);
 730             self.walk_stmts(&stmts[1..]);
 731         } else {
 732             self.walk_items(&items);
 733             self.walk_stmts(&stmts[items.len()..]);
 734         }
 735     }
 736
 737     fn walk_block_stmts(&mut self, b: &ast::Block) {
 738         self.walk_stmts(&b.stmts)
 739     }
 740
 741     fn format_mod(
 742         &mut self,
 743         m: &ast::Mod,
 744         vis: &ast::Visibility,
 745         s: Span,
 746         ident: ast::Ident,
 747         attrs: &[ast::Attribute],
 748     ) {
 749         // Decide whether this is an inline mod or an external mod.
 750         let local_file_name = self.codemap.span_to_filename(s);
 751         let inner_span = source!(self, m.inner);
 752         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 753             && local_file_name == self.codemap.span_to_filename(inner_span);
 754
 755         self.buffer.push_str(&*utils::format_visibility(vis));
 756         self.buffer.push_str("mod ");
 757         self.buffer.push_str(&ident.to_string());
 758
 759         if is_internal {
 760             match self.config.item_brace_style() {
 761                 BraceStyle::AlwaysNextLine => self.buffer
 762                     .push_str(&format!("\n{}{{", self.block_indent.to_string(self.config))),
 763                 _ => self.buffer.push_str(" {"),
 764             }
 765             // Hackery to account for the closing }.
 766             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 767             let body_snippet =
 768                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 769             let body_snippet = body_snippet.trim();
 770             if body_snippet.is_empty() {
 771                 self.buffer.push_str("}");
 772             } else {
 773                 self.last_pos = mod_lo;
 774                 self.block_indent = self.block_indent.block_indent(self.config);
 775                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 776                 self.walk_mod_items(m);
 777                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 778                 self.close_block(false);
 779             }
 780             self.last_pos = source!(self, m.inner).hi();
 781         } else {
 782             self.buffer.push_str(";");
 783             self.last_pos = source!(self, s).hi();
 784         }
 785     }
 786
 787     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 788         self.block_indent = Indent::empty();
 789         self.walk_mod_items(m);
 790         self.format_missing_with_indent(filemap.end_pos);
 791     }
 792
 793     pub fn get_context(&self) -> RewriteContext {
 794         RewriteContext {
 795             parse_session: self.parse_session,
 796             codemap: self.codemap,
 797             config: self.config,
 798             inside_macro: false,
 799             use_block: false,
 800             is_if_else_block: false,
 801             force_one_line_chain: false,
 802         }
 803     }
 804 }
 805
 806 impl Rewrite for ast::NestedMetaItem {
 807     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 808         match self.node {
 809             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 810             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 811         }
 812     }
 813 }
 814
 815 impl Rewrite for ast::MetaItem {
 816     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 817         Some(match self.node {
 818             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 819             ast::MetaItemKind::List(ref list) => {
 820                 let name = self.name.as_str();
 821                 // 1 = `(`, 2 = `]` and `)`
 822                 let item_shape = shape
 823                     .visual_indent(0)
 824                     .shrink_left(name.len() + 1)
 825                     .and_then(|s| s.sub_width(2))?;
 826                 let items = itemize_list(
 827                     context.codemap,
 828                     list.iter(),
 829                     ")",
 830                     |nested_meta_item| nested_meta_item.span.lo(),
 831                     |nested_meta_item| nested_meta_item.span.hi(),
 832                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 833                     self.span.lo(),
 834                     self.span.hi(),
 835                     false,
 836                 );
 837                 let item_vec = items.collect::<Vec<_>>();
 838                 let fmt = ListFormatting {
 839                     tactic: DefinitiveListTactic::Mixed,
 840                     separator: ",",
 841                     trailing_separator: SeparatorTactic::Never,
 842                     separator_place: SeparatorPlace::Back,
 843                     shape: item_shape,
 844                     ends_with_newline: false,
 845                     preserve_newline: false,
 846                     config: context.config,
 847                 };
 848                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 849             }
 850             ast::MetaItemKind::NameValue(ref literal) => {
 851                 let name = self.name.as_str();
 852                 // 3 = ` = `
 853                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 854                 let value = rewrite_literal(context, literal, lit_shape)?;
 855                 format!("{} = {}", name, value)
 856             }
 857         })
 858     }
 859 }
 860
 861 impl Rewrite for ast::Attribute {
 862     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 863         let prefix = match self.style {
 864             ast::AttrStyle::Inner => "#!",
 865             ast::AttrStyle::Outer => "#",
 866         };
 867         let snippet = context.snippet(self.span);
 868         if self.is_sugared_doc {
 869             let doc_shape = Shape {
 870                 width: cmp::min(shape.width, context.config.comment_width())
 871                     .checked_sub(shape.indent.width())
 872                     .unwrap_or(0),
 873                 ..shape
 874             };
 875             rewrite_comment(&snippet, false, doc_shape, context.config)
 876         } else {
 877             if contains_comment(&snippet) {
 878                 return Some(snippet);
 879             }
 880             // 1 = `[`
 881             let shape = shape.offset_left(prefix.len() + 1)?;
 882             self.meta()?
 883                 .rewrite(context, shape)
 884                 .map(|rw| format!("{}[{}]", prefix, rw))
 885         }
 886     }
 887 }
 888
 889 impl<'a> Rewrite for [ast::Attribute] {
 890     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 891         if self.is_empty() {
 892             return Some(String::new());
 893         }
 894         let mut result = String::with_capacity(128);
 895         let indent = shape.indent.to_string(context.config);
 896
 897         let mut derive_args = Vec::new();
 898
 899         let mut iter = self.iter().enumerate().peekable();
 900         let mut insert_new_line = true;
 901         let mut is_prev_sugared_doc = false;
 902         while let Some((i, a)) = iter.next() {
 903             let a_str = a.rewrite(context, shape)?;
 904
 905             // Write comments and blank lines between attributes.
 906             if i > 0 {
 907                 let comment = context.snippet(mk_sp(self[i - 1].span.hi(), a.span.lo()));
 908                 // This particular horror show is to preserve line breaks in between doc
 909                 // comments. An alternative would be to force such line breaks to start
 910                 // with the usual doc comment token.
 911                 let (multi_line_before, multi_line_after) = if a.is_sugared_doc
 912                     || is_prev_sugared_doc
 913                 {
 914                     // Look at before and after comment and see if there are any empty lines.
 915                     let comment_begin = comment.chars().position(|c| c == '/');
 916                     let len = comment_begin.unwrap_or_else(|| comment.len());
 917                     let mlb = comment.chars().take(len).filter(|c| *c == '\n').count() > 1;
 918                     let mla = if comment_begin.is_none() {
 919                         mlb
 920                     } else {
 921                         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 922                         let len = comment_end.unwrap();
 923                         comment
 924                             .chars()
 925                             .rev()
 926                             .take(len)
 927                             .filter(|c| *c == '\n')
 928                             .count() > 1
 929                     };
 930                     (mlb, mla)
 931                 } else {
 932                     (false, false)
 933                 };
 934
 935                 let comment = recover_missing_comment_in_span(
 936                     mk_sp(self[i - 1].span.hi(), a.span.lo()),
 937                     shape.with_max_width(context.config),
 938                     context,
 939                     0,
 940                 )?;
 941
 942                 if !comment.is_empty() {
 943                     if multi_line_before {
 944                         result.push('\n');
 945                     }
 946                     result.push_str(&comment);
 947                     result.push('\n');
 948                     if multi_line_after {
 949                         result.push('\n')
 950                     }
 951                 } else if insert_new_line {
 952                     result.push('\n');
 953                     if multi_line_after {
 954                         result.push('\n')
 955                     }
 956                 }
 957
 958                 if derive_args.is_empty() {
 959                     result.push_str(&indent);
 960                 }
 961
 962                 insert_new_line = true;
 963             }
 964
 965             // Write the attribute itself.
 966             if context.config.merge_derives() {
 967                 // If the attribute is `#[derive(...)]`, take the arguments.
 968                 if let Some(mut args) = get_derive_args(context, a) {
 969                     derive_args.append(&mut args);
 970                     match iter.peek() {
 971                         // If the next attribute is `#[derive(...)]` as well, skip rewriting.
 972                         Some(&(_, next_attr)) if is_derive(next_attr) => insert_new_line = false,
 973                         // If not, rewrite the merged derives.
 974                         _ => {
 975                             result.push_str(&format_derive(context, &derive_args, shape)?);
 976                             derive_args.clear();
 977                         }
 978                     }
 979                 } else {
 980                     result.push_str(&a_str);
 981                 }
 982             } else {
 983                 result.push_str(&a_str);
 984             }
 985
 986             is_prev_sugared_doc = a.is_sugared_doc;
 987         }
 988         Some(result)
 989     }
 990 }
 991
 992 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 993 fn format_derive(context: &RewriteContext, derive_args: &[String], shape: Shape) -> Option<String> {
 994     let mut result = String::with_capacity(128);
 995     result.push_str("#[derive(");
 996     // 11 = `#[derive()]`
 997     let initial_budget = shape.width.checked_sub(11)?;
 998     let mut budget = initial_budget;
 999     let num = derive_args.len();
1000     for (i, a) in derive_args.iter().enumerate() {
1001         // 2 = `, ` or `)]`
1002         let width = a.len() + 2;
1003         if width > budget {
1004             if i > 0 {
1005                 // Remove trailing whitespace.
1006                 result.pop();
1007             }
1008             result.push('\n');
1009             // 9 = `#[derive(`
1010             result.push_str(&(shape.indent + 9).to_string(context.config));
1011             budget = initial_budget;
1012         } else {
1013             budget = budget.checked_sub(width).unwrap_or(0);
1014         }
1015         result.push_str(a);
1016         if i != num - 1 {
1017             result.push_str(", ")
1018         }
1019     }
1020     result.push_str(")]");
1021     Some(result)
1022 }
1023
1024 fn is_derive(attr: &ast::Attribute) -> bool {
1025     match attr.meta() {
1026         Some(meta_item) => match meta_item.node {
1027             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1028             _ => false,
1029         },
1030         _ => false,
1031     }
1032 }
1033
1034 /// Returns the arguments of `#[derive(...)]`.
1035 fn get_derive_args(context: &RewriteContext, attr: &ast::Attribute) -> Option<Vec<String>> {
1036     attr.meta().and_then(|meta_item| match meta_item.node {
1037         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1038             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1039             Some(
1040                 args.iter()
1041                     .map(|a| context.snippet(a.span))
1042                     .collect::<Vec<_>>(),
1043             )
1044         }
1045         _ => None,
1046     })
1047 }
1048
1049 // Rewrite `extern crate foo;` WITHOUT attributes.
1050 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1051     assert!(is_extern_crate(item));
1052     let new_str = context.snippet(item.span);
1053     Some(if contains_comment(&new_str) {
1054         new_str
1055     } else {
1056         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1057         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1058     })
1059 }