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