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 syntax::{ast, visit};
  14 use syntax::attr::HasAttrs;
  15 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  16 use syntax::parse::ParseSess;
  17
  18 use expr::rewrite_literal;
  19 use spanned::Spanned;
  20 use codemap::{LineRangeUtils, SpanUtils};
  21 use comment::{combine_strs_with_missing_comments, contains_comment, remove_trailing_white_spaces,
  22               CodeCharKind, CommentCodeSlices, FindUncommented};
  23 use comment::rewrite_comment;
  24 use config::{BraceStyle, Config};
  25 use items::{format_impl, format_trait, format_trait_alias, rewrite_associated_impl_type,
  26             rewrite_associated_type, rewrite_type_alias, FnSig, StaticParts, StructParts};
  27 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  28             SeparatorTactic};
  29 use macros::{rewrite_macro, MacroPosition};
  30 use regex::Regex;
  31 use rewrite::{Rewrite, RewriteContext};
  32 use shape::{Indent, Shape};
  33 use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  34
  35 fn is_use_item(item: &ast::Item) -> bool {
  36     match item.node {
  37         ast::ItemKind::Use(_) => true,
  38         _ => false,
  39     }
  40 }
  41
  42 fn is_extern_crate(item: &ast::Item) -> bool {
  43     match item.node {
  44         ast::ItemKind::ExternCrate(..) => true,
  45         _ => false,
  46     }
  47 }
  48
  49 /// Creates a string slice corresponding to the specified span.
  50 pub struct SnippetProvider<'a> {
  51     /// A pointer to the content of the file we are formatting.
  52     big_snippet: &'a str,
  53     /// A position of the start of `big_snippet`, used as an offset.
  54     start_pos: usize,
  55 }
  56
  57 impl<'a> SnippetProvider<'a> {
  58     pub fn span_to_snippet(&self, span: Span) -> Option<&str> {
  59         let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
  60         let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
  61         Some(&self.big_snippet[start_index..end_index])
  62     }
  63
  64     pub fn new(start_pos: BytePos, big_snippet: &'a str) -> Self {
  65         let start_pos = start_pos.to_usize();
  66         SnippetProvider {
  67             big_snippet,
  68             start_pos,
  69         }
  70     }
  71 }
  72
  73 pub struct FmtVisitor<'a> {
  74     pub parse_session: &'a ParseSess,
  75     pub codemap: &'a CodeMap,
  76     pub buffer: String,
  77     pub last_pos: BytePos,
  78     // FIXME: use an RAII util or closure for indenting
  79     pub block_indent: Indent,
  80     pub config: &'a Config,
  81     pub is_if_else_block: bool,
  82     pub snippet_provider: &'a SnippetProvider<'a>,
  83     pub line_number: usize,
  84     pub skipped_range: Vec<(usize, usize)>,
  85 }
  86
  87 impl<'b, 'a: 'b> FmtVisitor<'a> {
  88     pub fn shape(&self) -> Shape {
  89         Shape::indented(self.block_indent, self.config)
  90     }
  91
  92     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  93         debug!(
  94             "visit_stmt: {:?} {:?}",
  95             self.codemap.lookup_char_pos(stmt.span.lo()),
  96             self.codemap.lookup_char_pos(stmt.span.hi())
  97         );
  98
  99         match stmt.node {
 100             ast::StmtKind::Item(ref item) => {
 101                 self.visit_item(item);
 102             }
 103             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 104                 if contains_skip(get_attrs_from_stmt(stmt)) {
 105                     self.push_skipped_with_span(stmt.span());
 106                 } else {
 107                     let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 108                     self.push_rewrite(stmt.span(), rewrite)
 109                 }
 110             }
 111             ast::StmtKind::Mac(ref mac) => {
 112                 let (ref mac, _macro_style, ref attrs) = **mac;
 113                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 114                     self.push_skipped_with_span(stmt.span());
 115                 } else {
 116                     self.visit_mac(mac, None, MacroPosition::Statement);
 117                 }
 118                 self.format_missing(stmt.span.hi());
 119             }
 120         }
 121     }
 122
 123     pub fn visit_block(
 124         &mut self,
 125         b: &ast::Block,
 126         inner_attrs: Option<&[ast::Attribute]>,
 127         has_braces: bool,
 128     ) {
 129         debug!(
 130             "visit_block: {:?} {:?}",
 131             self.codemap.lookup_char_pos(b.span.lo()),
 132             self.codemap.lookup_char_pos(b.span.hi())
 133         );
 134
 135         // Check if this block has braces.
 136         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 137
 138         self.last_pos = self.last_pos + brace_compensation;
 139         self.block_indent = self.block_indent.block_indent(self.config);
 140         self.push_str("{");
 141
 142         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 143             if let Some(first_stmt) = b.stmts.first() {
 144                 let attr_lo = inner_attrs
 145                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 146                     .or_else(|| {
 147                         // Attributes for an item in a statement position
 148                         // do not belong to the statement. (rust-lang/rust#34459)
 149                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 150                             item.attrs.first()
 151                         } else {
 152                             first_stmt.attrs().first()
 153                         }.and_then(|attr| {
 154                             // Some stmts can have embedded attributes.
 155                             // e.g. `match { #![attr] ... }`
 156                             let attr_lo = attr.span.lo();
 157                             if attr_lo < first_stmt.span.lo() {
 158                                 Some(attr_lo)
 159                             } else {
 160                                 None
 161                             }
 162                         })
 163                     });
 164
 165                 let snippet = self.snippet(mk_sp(
 166                     self.last_pos,
 167                     attr_lo.unwrap_or(first_stmt.span.lo()),
 168                 ));
 169                 let len = CommentCodeSlices::new(snippet)
 170                     .nth(0)
 171                     .and_then(|(kind, _, s)| {
 172                         if kind == CodeCharKind::Normal {
 173                             s.rfind('\n')
 174                         } else {
 175                             None
 176                         }
 177                     });
 178                 if let Some(len) = len {
 179                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 180                 }
 181             }
 182         }
 183
 184         // Format inner attributes if available.
 185         let skip_rewrite = if let Some(attrs) = inner_attrs {
 186             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 187         } else {
 188             false
 189         };
 190
 191         if skip_rewrite {
 192             self.push_rewrite(b.span, None);
 193             self.close_block(false);
 194             self.last_pos = source!(self, b.span).hi();
 195             return;
 196         }
 197
 198         self.walk_block_stmts(b);
 199
 200         if !b.stmts.is_empty() {
 201             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 202                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 203                     self.push_str(";");
 204                 }
 205             }
 206         }
 207
 208         let mut remove_len = BytePos(0);
 209         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 210             if let Some(stmt) = b.stmts.last() {
 211                 let snippet = self.snippet(mk_sp(
 212                     stmt.span.hi(),
 213                     source!(self, b.span).hi() - brace_compensation,
 214                 ));
 215                 let len = CommentCodeSlices::new(snippet)
 216                     .last()
 217                     .and_then(|(kind, _, s)| {
 218                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 219                             Some(s.len())
 220                         } else {
 221                             None
 222                         }
 223                     });
 224                 if let Some(len) = len {
 225                     remove_len = BytePos::from_usize(len);
 226                 }
 227             }
 228         }
 229
 230         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 231             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 232             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 233             snippet.contains("//") || snippet.contains("/*")
 234         };
 235         // FIXME: we should compress any newlines here to just one
 236         if unindent_comment {
 237             self.block_indent = self.block_indent.block_unindent(self.config);
 238         }
 239         self.format_missing_with_indent(
 240             source!(self, b.span).hi() - brace_compensation - remove_len,
 241         );
 242         if unindent_comment {
 243             self.block_indent = self.block_indent.block_indent(self.config);
 244         }
 245         self.close_block(unindent_comment);
 246         self.last_pos = source!(self, b.span).hi();
 247     }
 248
 249     // FIXME: this is a terrible hack to indent the comments between the last
 250     // item in the block and the closing brace to the block's level.
 251     // The closing brace itself, however, should be indented at a shallower
 252     // level.
 253     fn close_block(&mut self, unindent_comment: bool) {
 254         let total_len = self.buffer.len();
 255         let chars_too_many = if unindent_comment {
 256             0
 257         } else if self.config.hard_tabs() {
 258             1
 259         } else {
 260             self.config.tab_spaces()
 261         };
 262         self.buffer.truncate(total_len - chars_too_many);
 263         self.push_str("}");
 264         self.block_indent = self.block_indent.block_unindent(self.config);
 265     }
 266
 267     // Note that this only gets called for function definitions. Required methods
 268     // on traits do not get handled here.
 269     fn visit_fn(
 270         &mut self,
 271         fk: visit::FnKind,
 272         generics: &ast::Generics,
 273         fd: &ast::FnDecl,
 274         s: Span,
 275         defaultness: ast::Defaultness,
 276         inner_attrs: Option<&[ast::Attribute]>,
 277     ) {
 278         let indent = self.block_indent;
 279         let block;
 280         let rewrite = match fk {
 281             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 282                 block = b;
 283                 self.rewrite_fn(
 284                     indent,
 285                     ident,
 286                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 287                     mk_sp(s.lo(), b.span.lo()),
 288                     b,
 289                 )
 290             }
 291             visit::FnKind::Closure(_) => unreachable!(),
 292         };
 293
 294         if let Some(fn_str) = rewrite {
 295             self.format_missing_with_indent(source!(self, s).lo());
 296             self.push_str(&fn_str);
 297             if let Some(c) = fn_str.chars().last() {
 298                 if c == '}' {
 299                     self.last_pos = source!(self, block.span).hi();
 300                     return;
 301                 }
 302             }
 303         } else {
 304             self.format_missing(source!(self, block.span).lo());
 305         }
 306
 307         self.last_pos = source!(self, block.span).lo();
 308         self.visit_block(block, inner_attrs, true)
 309     }
 310
 311     pub fn visit_item(&mut self, item: &ast::Item) {
 312         skip_out_of_file_lines_range_visitor!(self, item.span);
 313
 314         // This is where we bail out if there is a skip attribute. This is only
 315         // complex in the module case. It is complex because the module could be
 316         // in a separate file and there might be attributes in both files, but
 317         // the AST lumps them all together.
 318         let filtered_attrs;
 319         let mut attrs = &item.attrs;
 320         match item.node {
 321             ast::ItemKind::Mod(ref m) => {
 322                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 323                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 324                 if outer_file.name == inner_file.name {
 325                     // Module is inline, in this case we treat modules like any
 326                     // other item.
 327                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 328                         self.push_skipped_with_span(item.span());
 329                         return;
 330                     }
 331                 } else if contains_skip(&item.attrs) {
 332                     // Module is not inline, but should be skipped.
 333                     return;
 334                 } else {
 335                     // Module is not inline and should not be skipped. We want
 336                     // to process only the attributes in the current file.
 337                     filtered_attrs = item.attrs
 338                         .iter()
 339                         .filter_map(|a| {
 340                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 341                             if attr_file.name == outer_file.name {
 342                                 Some(a.clone())
 343                             } else {
 344                                 None
 345                             }
 346                         })
 347                         .collect::<Vec<_>>();
 348                     // Assert because if we should skip it should be caught by
 349                     // the above case.
 350                     assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 351                     attrs = &filtered_attrs;
 352                 }
 353             }
 354             _ => {
 355                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 356                     self.push_skipped_with_span(item.span());
 357                     return;
 358                 }
 359             }
 360         }
 361
 362         match item.node {
 363             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 364             ast::ItemKind::Impl(..) => {
 365                 let snippet = self.snippet(item.span);
 366                 let where_span_end = snippet
 367                     .find_uncommented("{")
 368                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 369                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 370                 self.push_rewrite(item.span, rw);
 371             }
 372             ast::ItemKind::Trait(..) => {
 373                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 374                 self.push_rewrite(item.span, rw);
 375             }
 376             ast::ItemKind::TraitAlias(ref generics, ref ty_param_bounds) => {
 377                 let shape = Shape::indented(self.block_indent, self.config);
 378                 let rw = format_trait_alias(
 379                     &self.get_context(),
 380                     item.ident,
 381                     generics,
 382                     ty_param_bounds,
 383                     shape,
 384                 );
 385                 self.push_rewrite(item.span, rw);
 386             }
 387             ast::ItemKind::ExternCrate(_) => {
 388                 let rw = rewrite_extern_crate(&self.get_context(), item);
 389                 self.push_rewrite(item.span, rw);
 390             }
 391             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 392                 self.visit_struct(&StructParts::from_item(item));
 393             }
 394             ast::ItemKind::Enum(ref def, ref generics) => {
 395                 self.format_missing_with_indent(source!(self, item.span).lo());
 396                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 397                 self.last_pos = source!(self, item.span).hi();
 398             }
 399             ast::ItemKind::Mod(ref module) => {
 400                 self.format_missing_with_indent(source!(self, item.span).lo());
 401                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 402             }
 403             ast::ItemKind::Mac(ref mac) => {
 404                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 405             }
 406             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 407                 self.format_missing_with_indent(source!(self, item.span).lo());
 408                 self.format_foreign_mod(foreign_mod, item.span);
 409             }
 410             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 411                 self.visit_static(&StaticParts::from_item(item));
 412             }
 413             ast::ItemKind::AutoImpl(..) => {
 414                 // FIXME(#78): format impl definitions.
 415             }
 416             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 417                 self.visit_fn(
 418                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 419                     generics,
 420                     decl,
 421                     item.span,
 422                     ast::Defaultness::Final,
 423                     Some(&item.attrs),
 424                 )
 425             }
 426             ast::ItemKind::Ty(ref ty, ref generics) => {
 427                 let rewrite = rewrite_type_alias(
 428                     &self.get_context(),
 429                     self.block_indent,
 430                     item.ident,
 431                     ty,
 432                     generics,
 433                     &item.vis,
 434                     item.span,
 435                 );
 436                 self.push_rewrite(item.span, rewrite);
 437             }
 438             ast::ItemKind::GlobalAsm(..) => {
 439                 let snippet = Some(self.snippet(item.span).to_owned());
 440                 self.push_rewrite(item.span, snippet);
 441             }
 442             ast::ItemKind::MacroDef(..) => {
 443                 // FIXME(#1539): macros 2.0
 444                 let mac_snippet = Some(remove_trailing_white_spaces(self.snippet(item.span)));
 445                 self.push_rewrite(item.span, mac_snippet);
 446             }
 447         }
 448     }
 449
 450     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 451         skip_out_of_file_lines_range_visitor!(self, ti.span);
 452
 453         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 454             self.push_skipped_with_span(ti.span());
 455             return;
 456         }
 457
 458         match ti.node {
 459             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 460             ast::TraitItemKind::Method(ref sig, None) => {
 461                 let indent = self.block_indent;
 462                 let rewrite =
 463                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 464                 self.push_rewrite(ti.span, rewrite);
 465             }
 466             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 467                 self.visit_fn(
 468                     visit::FnKind::Method(ti.ident, sig, None, body),
 469                     &ti.generics,
 470                     &sig.decl,
 471                     ti.span,
 472                     ast::Defaultness::Final,
 473                     Some(&ti.attrs),
 474                 );
 475             }
 476             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 477                 let rewrite = rewrite_associated_type(
 478                     ti.ident,
 479                     type_default.as_ref(),
 480                     Some(type_param_bounds),
 481                     &self.get_context(),
 482                     self.block_indent,
 483                 );
 484                 self.push_rewrite(ti.span, rewrite);
 485             }
 486             ast::TraitItemKind::Macro(ref mac) => {
 487                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 488             }
 489         }
 490     }
 491
 492     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 493         skip_out_of_file_lines_range_visitor!(self, ii.span);
 494
 495         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 496             self.push_skipped_with_span(ii.span());
 497             return;
 498         }
 499
 500         match ii.node {
 501             ast::ImplItemKind::Method(ref sig, ref body) => {
 502                 self.visit_fn(
 503                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 504                     &ii.generics,
 505                     &sig.decl,
 506                     ii.span,
 507                     ii.defaultness,
 508                     Some(&ii.attrs),
 509                 );
 510             }
 511             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 512             ast::ImplItemKind::Type(ref ty) => {
 513                 let rewrite = rewrite_associated_impl_type(
 514                     ii.ident,
 515                     ii.defaultness,
 516                     Some(ty),
 517                     None,
 518                     &self.get_context(),
 519                     self.block_indent,
 520                 );
 521                 self.push_rewrite(ii.span, rewrite);
 522             }
 523             ast::ImplItemKind::Macro(ref mac) => {
 524                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 525             }
 526         }
 527     }
 528
 529     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 530         skip_out_of_file_lines_range_visitor!(self, mac.span);
 531
 532         // 1 = ;
 533         let shape = self.shape().sub_width(1).unwrap();
 534         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 535         self.push_rewrite(mac.span, rewrite);
 536     }
 537
 538     pub fn push_str(&mut self, s: &str) {
 539         self.line_number += count_newlines(s);
 540         self.buffer.push_str(s);
 541     }
 542
 543     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 544         if let Some(ref s) = rewrite {
 545             self.push_str(s);
 546         } else {
 547             let snippet = self.snippet(span);
 548             self.push_str(snippet);
 549         }
 550         self.last_pos = source!(self, span).hi();
 551     }
 552
 553     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 554         self.format_missing_with_indent(source!(self, span).lo());
 555         self.push_rewrite_inner(span, rewrite);
 556     }
 557
 558     pub fn push_skipped_with_span(&mut self, span: Span) {
 559         self.format_missing_with_indent(source!(self, span).lo());
 560         let lo = self.line_number + 1;
 561         self.push_rewrite_inner(span, None);
 562         let hi = self.line_number + 1;
 563         self.skipped_range.push((lo, hi));
 564     }
 565
 566     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 567         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 568     }
 569
 570     pub fn from_codemap(
 571         parse_session: &'a ParseSess,
 572         config: &'a Config,
 573         snippet_provider: &'a SnippetProvider,
 574     ) -> FmtVisitor<'a> {
 575         FmtVisitor {
 576             parse_session: parse_session,
 577             codemap: parse_session.codemap(),
 578             buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
 579             last_pos: BytePos(0),
 580             block_indent: Indent::empty(),
 581             config: config,
 582             is_if_else_block: false,
 583             snippet_provider: snippet_provider,
 584             line_number: 0,
 585             skipped_range: vec![],
 586         }
 587     }
 588
 589     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 590         self.snippet_provider.span_to_snippet(span)
 591     }
 592
 593     pub fn snippet(&'b self, span: Span) -> &'a str {
 594         self.opt_snippet(span).unwrap()
 595     }
 596
 597     // Returns true if we should skip the following item.
 598     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 599         if contains_skip(attrs) {
 600             return true;
 601         }
 602
 603         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 604         if attrs.is_empty() {
 605             return false;
 606         }
 607
 608         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 609         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 610         self.push_rewrite(span, rewrite);
 611
 612         false
 613     }
 614
 615     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 616     where
 617         F: Fn(&ast::Item) -> bool,
 618     {
 619         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 620         let item_length = items_left
 621             .iter()
 622             .take_while(|ppi| {
 623                 is_item(&***ppi) && (!in_group || {
 624                     let current = self.codemap.lookup_line_range(ppi.span());
 625                     let in_same_group = current.lo < last.hi + 2;
 626                     last = current;
 627                     in_same_group
 628                 })
 629             })
 630             .count();
 631         let items = &items_left[..item_length];
 632
 633         let at_least_one_in_file_lines = items
 634             .iter()
 635             .any(|item| !out_of_file_lines_range!(self, item.span));
 636
 637         if at_least_one_in_file_lines {
 638             self.format_imports(items);
 639         } else {
 640             for item in items {
 641                 self.push_rewrite(item.span, None);
 642             }
 643         }
 644
 645         item_length
 646     }
 647
 648     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 649         while !items_left.is_empty() {
 650             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 651             // to be potentially reordered within `format_imports`. Otherwise, just format the
 652             // next item for output.
 653             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 654                 let used_items_len = self.reorder_items(
 655                     items_left,
 656                     &is_use_item,
 657                     self.config.reorder_imports_in_group(),
 658                 );
 659                 let (_, rest) = items_left.split_at(used_items_len);
 660                 items_left = rest;
 661             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 662                 let used_items_len = self.reorder_items(
 663                     items_left,
 664                     &is_extern_crate,
 665                     self.config.reorder_extern_crates_in_group(),
 666                 );
 667                 let (_, rest) = items_left.split_at(used_items_len);
 668                 items_left = rest;
 669             } else {
 670                 // `unwrap()` is safe here because we know `items_left`
 671                 // has elements from the loop condition
 672                 let (item, rest) = items_left.split_first().unwrap();
 673                 self.visit_item(item);
 674                 items_left = rest;
 675             }
 676         }
 677     }
 678
 679     fn walk_mod_items(&mut self, m: &ast::Mod) {
 680         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 681     }
 682
 683     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 684         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 685             match stmt.node {
 686                 ast::StmtKind::Item(ref item) => Some(&**item),
 687                 _ => None,
 688             }
 689         }
 690
 691         if stmts.is_empty() {
 692             return;
 693         }
 694
 695         // Extract leading `use ...;`.
 696         let items: Vec<_> = stmts
 697             .iter()
 698             .take_while(|stmt| to_stmt_item(stmt).map_or(false, is_use_item))
 699             .filter_map(|stmt| to_stmt_item(stmt))
 700             .collect();
 701
 702         if items.is_empty() {
 703             self.visit_stmt(&stmts[0]);
 704             self.walk_stmts(&stmts[1..]);
 705         } else {
 706             self.walk_items(&items);
 707             self.walk_stmts(&stmts[items.len()..]);
 708         }
 709     }
 710
 711     fn walk_block_stmts(&mut self, b: &ast::Block) {
 712         self.walk_stmts(&b.stmts)
 713     }
 714
 715     fn format_mod(
 716         &mut self,
 717         m: &ast::Mod,
 718         vis: &ast::Visibility,
 719         s: Span,
 720         ident: ast::Ident,
 721         attrs: &[ast::Attribute],
 722     ) {
 723         // Decide whether this is an inline mod or an external mod.
 724         let local_file_name = self.codemap.span_to_filename(s);
 725         let inner_span = source!(self, m.inner);
 726         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 727             && local_file_name == self.codemap.span_to_filename(inner_span);
 728
 729         self.push_str(&*utils::format_visibility(vis));
 730         self.push_str("mod ");
 731         self.push_str(&ident.to_string());
 732
 733         if is_internal {
 734             match self.config.brace_style() {
 735                 BraceStyle::AlwaysNextLine => {
 736                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 737                     self.push_str(&sep_str);
 738                 }
 739                 _ => self.push_str(" {"),
 740             }
 741             // Hackery to account for the closing }.
 742             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 743             let body_snippet =
 744                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 745             let body_snippet = body_snippet.trim();
 746             if body_snippet.is_empty() {
 747                 self.push_str("}");
 748             } else {
 749                 self.last_pos = mod_lo;
 750                 self.block_indent = self.block_indent.block_indent(self.config);
 751                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 752                 self.walk_mod_items(m);
 753                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 754                 self.close_block(false);
 755             }
 756             self.last_pos = source!(self, m.inner).hi();
 757         } else {
 758             self.push_str(";");
 759             self.last_pos = source!(self, s).hi();
 760         }
 761     }
 762
 763     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 764         self.block_indent = Indent::empty();
 765         self.walk_mod_items(m);
 766         self.format_missing_with_indent(filemap.end_pos);
 767     }
 768
 769     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 770         while let Some(pos) = self.codemap
 771             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 772         {
 773             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 774                 if snippet.trim().is_empty() {
 775                     self.last_pos = pos;
 776                 } else {
 777                     return;
 778                 }
 779             }
 780         }
 781     }
 782
 783     pub fn get_context(&self) -> RewriteContext {
 784         RewriteContext {
 785             parse_session: self.parse_session,
 786             codemap: self.codemap,
 787             config: self.config,
 788             inside_macro: false,
 789             use_block: false,
 790             is_if_else_block: false,
 791             force_one_line_chain: false,
 792             snippet_provider: self.snippet_provider,
 793         }
 794     }
 795 }
 796
 797 impl Rewrite for ast::NestedMetaItem {
 798     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 799         match self.node {
 800             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 801             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 802         }
 803     }
 804 }
 805
 806 impl Rewrite for ast::MetaItem {
 807     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 808         Some(match self.node {
 809             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 810             ast::MetaItemKind::List(ref list) => {
 811                 let name = self.name.as_str();
 812                 // 1 = `(`, 2 = `]` and `)`
 813                 let item_shape = shape
 814                     .visual_indent(0)
 815                     .shrink_left(name.len() + 1)
 816                     .and_then(|s| s.sub_width(2))?;
 817                 let items = itemize_list(
 818                     context.codemap,
 819                     list.iter(),
 820                     ")",
 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.to_owned());
 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 /// Returns the first group of attributes that fills the given predicate.
 882 /// We consider two doc comments are in different group if they are separated by normal comments.
 883 fn take_while_with_pred<'a, P>(
 884     context: &RewriteContext,
 885     attrs: &'a [ast::Attribute],
 886     pred: P,
 887 ) -> &'a [ast::Attribute]
 888 where
 889     P: Fn(&ast::Attribute) -> bool,
 890 {
 891     let mut last_index = 0;
 892     let mut iter = attrs.iter().enumerate().peekable();
 893     while let Some((i, attr)) = iter.next() {
 894         if !pred(attr) {
 895             break;
 896         }
 897         if let Some(&(_, next_attr)) = iter.peek() {
 898             // Extract comments between two attributes.
 899             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 900             let snippet = context.snippet(span_between_attr);
 901             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 902                 break;
 903             }
 904         }
 905         last_index = i;
 906     }
 907     if last_index == 0 {
 908         &[]
 909     } else {
 910         &attrs[..last_index + 1]
 911     }
 912 }
 913
 914 fn rewrite_first_group_attrs(
 915     context: &RewriteContext,
 916     attrs: &[ast::Attribute],
 917     shape: Shape,
 918 ) -> Option<(usize, String)> {
 919     if attrs.is_empty() {
 920         return Some((0, String::new()));
 921     }
 922     // Rewrite doc comments
 923     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 924     if !sugared_docs.is_empty() {
 925         let snippet = sugared_docs
 926             .iter()
 927             .map(|a| context.snippet(a.span))
 928             .collect::<Vec<_>>()
 929             .join("\n");
 930         return Some((
 931             sugared_docs.len(),
 932             rewrite_comment(&snippet, false, shape, context.config)?,
 933         ));
 934     }
 935     // Rewrite `#[derive(..)]`s.
 936     if context.config.merge_derives() {
 937         let derives = take_while_with_pred(context, attrs, is_derive);
 938         if !derives.is_empty() {
 939             let mut derive_args = vec![];
 940             for derive in derives {
 941                 derive_args.append(&mut get_derive_args(context, derive)?);
 942             }
 943             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 944         }
 945     }
 946     // Rewrite the first attribute.
 947     Some((1, attrs[0].rewrite(context, shape)?))
 948 }
 949
 950 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 951     // Look at before and after comment and see if there are any empty lines.
 952     let comment_begin = comment.chars().position(|c| c == '/');
 953     let len = comment_begin.unwrap_or_else(|| comment.len());
 954     let mlb = count_newlines(&comment[..len]) > 1;
 955     let mla = if comment_begin.is_none() {
 956         mlb
 957     } else {
 958         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 959         let len = comment_end.unwrap();
 960         comment
 961             .chars()
 962             .rev()
 963             .take(len)
 964             .filter(|c| *c == '\n')
 965             .count() > 1
 966     };
 967     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 968 }
 969
 970 impl<'a> Rewrite for [ast::Attribute] {
 971     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 972         if self.is_empty() {
 973             return Some(String::new());
 974         }
 975         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 976         if self.len() == 1 || first_group_len == self.len() {
 977             Some(first_group_str)
 978         } else {
 979             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 980             let missing_span = mk_sp(
 981                 self[first_group_len - 1].span.hi(),
 982                 self[first_group_len].span.lo(),
 983             );
 984             // Preserve an empty line before/after doc comments.
 985             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 986                 let snippet = context.snippet(missing_span);
 987                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
 988                 let comment = ::comment::recover_missing_comment_in_span(
 989                     missing_span,
 990                     shape.with_max_width(context.config),
 991                     context,
 992                     0,
 993                 )?;
 994                 let comment = if comment.is_empty() {
 995                     format!("\n{}", mlb)
 996                 } else {
 997                     format!("{}{}\n{}", mla, comment, mlb)
 998                 };
 999                 Some(format!(
1000                     "{}{}{}{}",
1001                     first_group_str,
1002                     comment,
1003                     shape.indent.to_string(context.config),
1004                     rest_str
1005                 ))
1006             } else {
1007                 combine_strs_with_missing_comments(
1008                     context,
1009                     &first_group_str,
1010                     &rest_str,
1011                     missing_span,
1012                     shape,
1013                     false,
1014                 )
1015             }
1016         }
1017     }
1018 }
1019
1020 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1021 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1022     let mut result = String::with_capacity(128);
1023     result.push_str("#[derive(");
1024     // 11 = `#[derive()]`
1025     let initial_budget = shape.width.checked_sub(11)?;
1026     let mut budget = initial_budget;
1027     let num = derive_args.len();
1028     for (i, a) in derive_args.iter().enumerate() {
1029         // 2 = `, ` or `)]`
1030         let width = a.len() + 2;
1031         if width > budget {
1032             if i > 0 {
1033                 // Remove trailing whitespace.
1034                 result.pop();
1035             }
1036             result.push('\n');
1037             // 9 = `#[derive(`
1038             result.push_str(&(shape.indent + 9).to_string(context.config));
1039             budget = initial_budget;
1040         } else {
1041             budget = budget.checked_sub(width).unwrap_or(0);
1042         }
1043         result.push_str(a);
1044         if i != num - 1 {
1045             result.push_str(", ")
1046         }
1047     }
1048     result.push_str(")]");
1049     Some(result)
1050 }
1051
1052 fn is_derive(attr: &ast::Attribute) -> bool {
1053     match attr.meta() {
1054         Some(meta_item) => match meta_item.node {
1055             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1056             _ => false,
1057         },
1058         _ => false,
1059     }
1060 }
1061
1062 /// Returns the arguments of `#[derive(...)]`.
1063 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1064     attr.meta().and_then(|meta_item| match meta_item.node {
1065         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1066             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1067             Some(
1068                 args.iter()
1069                     .map(|a| context.snippet(a.span))
1070                     .collect::<Vec<_>>(),
1071             )
1072         }
1073         _ => None,
1074     })
1075 }
1076
1077 // Rewrite `extern crate foo;` WITHOUT attributes.
1078 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1079     assert!(is_extern_crate(item));
1080     let new_str = context.snippet(item.span);
1081     Some(if contains_comment(new_str) {
1082         new_str.to_owned()
1083     } else {
1084         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1085         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1086     })
1087 }
1088
1089 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1090     match stmt.node {
1091         ast::StmtKind::Local(ref local) => &local.attrs,
1092         ast::StmtKind::Item(ref item) => &item.attrs,
1093         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1094         ast::StmtKind::Mac(ref mac) => &mac.2,
1095     }
1096 }