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 codemap::{LineRangeUtils, SpanUtils};
  19 use comment::{combine_strs_with_missing_comments, contains_comment, CodeCharKind,
  20               CommentCodeSlices, FindUncommented};
  21 use comment::rewrite_comment;
  22 use config::{BraceStyle, Config};
  23 use expr::rewrite_literal;
  24 use items::{format_impl, format_trait, format_trait_alias, rewrite_associated_impl_type,
  25             rewrite_associated_type, rewrite_type_alias, FnSig, StaticParts, StructParts};
  26 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  27             SeparatorTactic};
  28 use macros::{rewrite_macro, rewrite_macro_def, MacroPosition};
  29 use regex::Regex;
  30 use rewrite::{Rewrite, RewriteContext};
  31 use shape::{Indent, Shape};
  32 use spanned::Spanned;
  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::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 414                 self.visit_fn(
 415                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 416                     generics,
 417                     decl,
 418                     item.span,
 419                     ast::Defaultness::Final,
 420                     Some(&item.attrs),
 421                 )
 422             }
 423             ast::ItemKind::Ty(ref ty, ref generics) => {
 424                 let rewrite = rewrite_type_alias(
 425                     &self.get_context(),
 426                     self.block_indent,
 427                     item.ident,
 428                     ty,
 429                     generics,
 430                     &item.vis,
 431                     item.span,
 432                 );
 433                 self.push_rewrite(item.span, rewrite);
 434             }
 435             ast::ItemKind::GlobalAsm(..) => {
 436                 let snippet = Some(self.snippet(item.span).to_owned());
 437                 self.push_rewrite(item.span, snippet);
 438             }
 439             ast::ItemKind::MacroDef(ref def) => {
 440                 let rewrite = rewrite_macro_def(
 441                     &self.get_context(),
 442                     self.block_indent,
 443                     def,
 444                     item.ident,
 445                     &item.vis,
 446                     item.span,
 447                 );
 448                 self.push_rewrite(item.span, rewrite);
 449             }
 450         }
 451     }
 452
 453     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 454         skip_out_of_file_lines_range_visitor!(self, ti.span);
 455
 456         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 457             self.push_skipped_with_span(ti.span());
 458             return;
 459         }
 460
 461         match ti.node {
 462             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 463             ast::TraitItemKind::Method(ref sig, None) => {
 464                 let indent = self.block_indent;
 465                 let rewrite =
 466                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 467                 self.push_rewrite(ti.span, rewrite);
 468             }
 469             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 470                 self.visit_fn(
 471                     visit::FnKind::Method(ti.ident, sig, None, body),
 472                     &ti.generics,
 473                     &sig.decl,
 474                     ti.span,
 475                     ast::Defaultness::Final,
 476                     Some(&ti.attrs),
 477                 );
 478             }
 479             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 480                 let rewrite = rewrite_associated_type(
 481                     ti.ident,
 482                     type_default.as_ref(),
 483                     Some(type_param_bounds),
 484                     &self.get_context(),
 485                     self.block_indent,
 486                 );
 487                 self.push_rewrite(ti.span, rewrite);
 488             }
 489             ast::TraitItemKind::Macro(ref mac) => {
 490                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 491             }
 492         }
 493     }
 494
 495     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 496         skip_out_of_file_lines_range_visitor!(self, ii.span);
 497
 498         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 499             self.push_skipped_with_span(ii.span());
 500             return;
 501         }
 502
 503         match ii.node {
 504             ast::ImplItemKind::Method(ref sig, ref body) => {
 505                 self.visit_fn(
 506                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 507                     &ii.generics,
 508                     &sig.decl,
 509                     ii.span,
 510                     ii.defaultness,
 511                     Some(&ii.attrs),
 512                 );
 513             }
 514             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 515             ast::ImplItemKind::Type(ref ty) => {
 516                 let rewrite = rewrite_associated_impl_type(
 517                     ii.ident,
 518                     ii.defaultness,
 519                     Some(ty),
 520                     None,
 521                     &self.get_context(),
 522                     self.block_indent,
 523                 );
 524                 self.push_rewrite(ii.span, rewrite);
 525             }
 526             ast::ImplItemKind::Macro(ref mac) => {
 527                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 528             }
 529         }
 530     }
 531
 532     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 533         skip_out_of_file_lines_range_visitor!(self, mac.span);
 534
 535         // 1 = ;
 536         let shape = self.shape().sub_width(1).unwrap();
 537         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 538         self.push_rewrite(mac.span, rewrite);
 539     }
 540
 541     pub fn push_str(&mut self, s: &str) {
 542         self.line_number += count_newlines(s);
 543         self.buffer.push_str(s);
 544     }
 545
 546     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 547         if let Some(ref s) = rewrite {
 548             self.push_str(s);
 549         } else {
 550             let snippet = self.snippet(span);
 551             self.push_str(snippet);
 552         }
 553         self.last_pos = source!(self, span).hi();
 554     }
 555
 556     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 557         self.format_missing_with_indent(source!(self, span).lo());
 558         self.push_rewrite_inner(span, rewrite);
 559     }
 560
 561     pub fn push_skipped_with_span(&mut self, span: Span) {
 562         self.format_missing_with_indent(source!(self, span).lo());
 563         let lo = self.line_number + 1;
 564         self.push_rewrite_inner(span, None);
 565         let hi = self.line_number + 1;
 566         self.skipped_range.push((lo, hi));
 567     }
 568
 569     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 570         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 571     }
 572
 573     pub fn from_codemap(
 574         parse_session: &'a ParseSess,
 575         config: &'a Config,
 576         snippet_provider: &'a SnippetProvider,
 577     ) -> FmtVisitor<'a> {
 578         FmtVisitor {
 579             parse_session,
 580             codemap: parse_session.codemap(),
 581             buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
 582             last_pos: BytePos(0),
 583             block_indent: Indent::empty(),
 584             config,
 585             is_if_else_block: false,
 586             snippet_provider,
 587             line_number: 0,
 588             skipped_range: vec![],
 589         }
 590     }
 591
 592     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 593         self.snippet_provider.span_to_snippet(span)
 594     }
 595
 596     pub fn snippet(&'b self, span: Span) -> &'a str {
 597         self.opt_snippet(span).unwrap()
 598     }
 599
 600     // Returns true if we should skip the following item.
 601     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 602         if contains_skip(attrs) {
 603             return true;
 604         }
 605
 606         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 607         if attrs.is_empty() {
 608             return false;
 609         }
 610
 611         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 612         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 613         self.push_rewrite(span, rewrite);
 614
 615         false
 616     }
 617
 618     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 619     where
 620         F: Fn(&ast::Item) -> bool,
 621     {
 622         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 623         let item_length = items_left
 624             .iter()
 625             .take_while(|ppi| {
 626                 is_item(&***ppi) && (!in_group || {
 627                     let current = self.codemap.lookup_line_range(ppi.span());
 628                     let in_same_group = current.lo < last.hi + 2;
 629                     last = current;
 630                     in_same_group
 631                 })
 632             })
 633             .count();
 634         let items = &items_left[..item_length];
 635
 636         let at_least_one_in_file_lines = items
 637             .iter()
 638             .any(|item| !out_of_file_lines_range!(self, item.span));
 639
 640         if at_least_one_in_file_lines {
 641             self.format_imports(items);
 642         } else {
 643             for item in items {
 644                 self.push_rewrite(item.span, None);
 645             }
 646         }
 647
 648         item_length
 649     }
 650
 651     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 652         while !items_left.is_empty() {
 653             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 654             // to be potentially reordered within `format_imports`. Otherwise, just format the
 655             // next item for output.
 656             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 657                 let used_items_len = self.reorder_items(
 658                     items_left,
 659                     &is_use_item,
 660                     self.config.reorder_imports_in_group(),
 661                 );
 662                 let (_, rest) = items_left.split_at(used_items_len);
 663                 items_left = rest;
 664             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 665                 let used_items_len = self.reorder_items(
 666                     items_left,
 667                     &is_extern_crate,
 668                     self.config.reorder_extern_crates_in_group(),
 669                 );
 670                 let (_, rest) = items_left.split_at(used_items_len);
 671                 items_left = rest;
 672             } else {
 673                 // `unwrap()` is safe here because we know `items_left`
 674                 // has elements from the loop condition
 675                 let (item, rest) = items_left.split_first().unwrap();
 676                 self.visit_item(item);
 677                 items_left = rest;
 678             }
 679         }
 680     }
 681
 682     fn walk_mod_items(&mut self, m: &ast::Mod) {
 683         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 684     }
 685
 686     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 687         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 688             match stmt.node {
 689                 ast::StmtKind::Item(ref item) => Some(&**item),
 690                 _ => None,
 691             }
 692         }
 693
 694         if stmts.is_empty() {
 695             return;
 696         }
 697
 698         // Extract leading `use ...;`.
 699         let items: Vec<_> = stmts
 700             .iter()
 701             .take_while(|stmt| to_stmt_item(stmt).map_or(false, is_use_item))
 702             .filter_map(|stmt| to_stmt_item(stmt))
 703             .collect();
 704
 705         if items.is_empty() {
 706             self.visit_stmt(&stmts[0]);
 707             self.walk_stmts(&stmts[1..]);
 708         } else {
 709             self.walk_items(&items);
 710             self.walk_stmts(&stmts[items.len()..]);
 711         }
 712     }
 713
 714     fn walk_block_stmts(&mut self, b: &ast::Block) {
 715         self.walk_stmts(&b.stmts)
 716     }
 717
 718     fn format_mod(
 719         &mut self,
 720         m: &ast::Mod,
 721         vis: &ast::Visibility,
 722         s: Span,
 723         ident: ast::Ident,
 724         attrs: &[ast::Attribute],
 725     ) {
 726         // Decide whether this is an inline mod or an external mod.
 727         let local_file_name = self.codemap.span_to_filename(s);
 728         let inner_span = source!(self, m.inner);
 729         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 730             && local_file_name == self.codemap.span_to_filename(inner_span);
 731
 732         self.push_str(&*utils::format_visibility(vis));
 733         self.push_str("mod ");
 734         self.push_str(&ident.to_string());
 735
 736         if is_internal {
 737             match self.config.brace_style() {
 738                 BraceStyle::AlwaysNextLine => {
 739                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 740                     self.push_str(&sep_str);
 741                 }
 742                 _ => self.push_str(" {"),
 743             }
 744             // Hackery to account for the closing }.
 745             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 746             let body_snippet =
 747                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 748             let body_snippet = body_snippet.trim();
 749             if body_snippet.is_empty() {
 750                 self.push_str("}");
 751             } else {
 752                 self.last_pos = mod_lo;
 753                 self.block_indent = self.block_indent.block_indent(self.config);
 754                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 755                 self.walk_mod_items(m);
 756                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 757                 self.close_block(false);
 758             }
 759             self.last_pos = source!(self, m.inner).hi();
 760         } else {
 761             self.push_str(";");
 762             self.last_pos = source!(self, s).hi();
 763         }
 764     }
 765
 766     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 767         self.block_indent = Indent::empty();
 768         self.walk_mod_items(m);
 769         self.format_missing_with_indent(filemap.end_pos);
 770     }
 771
 772     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 773         while let Some(pos) = self.codemap
 774             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 775         {
 776             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 777                 if snippet.trim().is_empty() {
 778                     self.last_pos = pos;
 779                 } else {
 780                     return;
 781                 }
 782             }
 783         }
 784     }
 785
 786     pub fn get_context(&self) -> RewriteContext {
 787         RewriteContext {
 788             parse_session: self.parse_session,
 789             codemap: self.codemap,
 790             config: self.config,
 791             inside_macro: false,
 792             use_block: false,
 793             is_if_else_block: false,
 794             force_one_line_chain: false,
 795             snippet_provider: self.snippet_provider,
 796         }
 797     }
 798 }
 799
 800 impl Rewrite for ast::NestedMetaItem {
 801     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 802         match self.node {
 803             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 804             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 805         }
 806     }
 807 }
 808
 809 impl Rewrite for ast::MetaItem {
 810     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 811         Some(match self.node {
 812             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 813             ast::MetaItemKind::List(ref list) => {
 814                 let name = self.name.as_str();
 815                 // 1 = `(`, 2 = `]` and `)`
 816                 let item_shape = shape
 817                     .visual_indent(0)
 818                     .shrink_left(name.len() + 1)
 819                     .and_then(|s| s.sub_width(2))?;
 820                 let items = itemize_list(
 821                     context.codemap,
 822                     list.iter(),
 823                     ")",
 824                     ",",
 825                     |nested_meta_item| nested_meta_item.span.lo(),
 826                     |nested_meta_item| nested_meta_item.span.hi(),
 827                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 828                     self.span.lo(),
 829                     self.span.hi(),
 830                     false,
 831                 );
 832                 let item_vec = items.collect::<Vec<_>>();
 833                 let fmt = ListFormatting {
 834                     tactic: DefinitiveListTactic::Mixed,
 835                     separator: ",",
 836                     trailing_separator: SeparatorTactic::Never,
 837                     separator_place: SeparatorPlace::Back,
 838                     shape: item_shape,
 839                     ends_with_newline: false,
 840                     preserve_newline: false,
 841                     config: context.config,
 842                 };
 843                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 844             }
 845             ast::MetaItemKind::NameValue(ref literal) => {
 846                 let name = self.name.as_str();
 847                 // 3 = ` = `
 848                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 849                 let value = rewrite_literal(context, literal, lit_shape)?;
 850                 format!("{} = {}", name, value)
 851             }
 852         })
 853     }
 854 }
 855
 856 impl Rewrite for ast::Attribute {
 857     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 858         let prefix = match self.style {
 859             ast::AttrStyle::Inner => "#!",
 860             ast::AttrStyle::Outer => "#",
 861         };
 862         let snippet = context.snippet(self.span);
 863         if self.is_sugared_doc {
 864             let doc_shape = Shape {
 865                 width: cmp::min(shape.width, context.config.comment_width())
 866                     .checked_sub(shape.indent.width())
 867                     .unwrap_or(0),
 868                 ..shape
 869             };
 870             rewrite_comment(snippet, false, doc_shape, context.config)
 871         } else {
 872             if contains_comment(snippet) {
 873                 return Some(snippet.to_owned());
 874             }
 875             // 1 = `[`
 876             let shape = shape.offset_left(prefix.len() + 1)?;
 877             self.meta()?
 878                 .rewrite(context, shape)
 879                 .map(|rw| format!("{}[{}]", prefix, rw))
 880         }
 881     }
 882 }
 883
 884 /// Returns the first group of attributes that fills the given predicate.
 885 /// We consider two doc comments are in different group if they are separated by normal comments.
 886 fn take_while_with_pred<'a, P>(
 887     context: &RewriteContext,
 888     attrs: &'a [ast::Attribute],
 889     pred: P,
 890 ) -> &'a [ast::Attribute]
 891 where
 892     P: Fn(&ast::Attribute) -> bool,
 893 {
 894     let mut last_index = 0;
 895     let mut iter = attrs.iter().enumerate().peekable();
 896     while let Some((i, attr)) = iter.next() {
 897         if !pred(attr) {
 898             break;
 899         }
 900         if let Some(&(_, next_attr)) = iter.peek() {
 901             // Extract comments between two attributes.
 902             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 903             let snippet = context.snippet(span_between_attr);
 904             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 905                 break;
 906             }
 907         }
 908         last_index = i;
 909     }
 910     if last_index == 0 {
 911         &[]
 912     } else {
 913         &attrs[..last_index + 1]
 914     }
 915 }
 916
 917 fn rewrite_first_group_attrs(
 918     context: &RewriteContext,
 919     attrs: &[ast::Attribute],
 920     shape: Shape,
 921 ) -> Option<(usize, String)> {
 922     if attrs.is_empty() {
 923         return Some((0, String::new()));
 924     }
 925     // Rewrite doc comments
 926     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 927     if !sugared_docs.is_empty() {
 928         let snippet = sugared_docs
 929             .iter()
 930             .map(|a| context.snippet(a.span))
 931             .collect::<Vec<_>>()
 932             .join("\n");
 933         return Some((
 934             sugared_docs.len(),
 935             rewrite_comment(&snippet, false, shape, context.config)?,
 936         ));
 937     }
 938     // Rewrite `#[derive(..)]`s.
 939     if context.config.merge_derives() {
 940         let derives = take_while_with_pred(context, attrs, is_derive);
 941         if !derives.is_empty() {
 942             let mut derive_args = vec![];
 943             for derive in derives {
 944                 derive_args.append(&mut get_derive_args(context, derive)?);
 945             }
 946             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 947         }
 948     }
 949     // Rewrite the first attribute.
 950     Some((1, attrs[0].rewrite(context, shape)?))
 951 }
 952
 953 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 954     // Look at before and after comment and see if there are any empty lines.
 955     let comment_begin = comment.chars().position(|c| c == '/');
 956     let len = comment_begin.unwrap_or_else(|| comment.len());
 957     let mlb = count_newlines(&comment[..len]) > 1;
 958     let mla = if comment_begin.is_none() {
 959         mlb
 960     } else {
 961         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 962         let len = comment_end.unwrap();
 963         comment
 964             .chars()
 965             .rev()
 966             .take(len)
 967             .filter(|c| *c == '\n')
 968             .count() > 1
 969     };
 970     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 971 }
 972
 973 impl<'a> Rewrite for [ast::Attribute] {
 974     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 975         if self.is_empty() {
 976             return Some(String::new());
 977         }
 978         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 979         if self.len() == 1 || first_group_len == self.len() {
 980             Some(first_group_str)
 981         } else {
 982             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 983             let missing_span = mk_sp(
 984                 self[first_group_len - 1].span.hi(),
 985                 self[first_group_len].span.lo(),
 986             );
 987             // Preserve an empty line before/after doc comments.
 988             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 989                 let snippet = context.snippet(missing_span);
 990                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
 991                 let comment = ::comment::recover_missing_comment_in_span(
 992                     missing_span,
 993                     shape.with_max_width(context.config),
 994                     context,
 995                     0,
 996                 )?;
 997                 let comment = if comment.is_empty() {
 998                     format!("\n{}", mlb)
 999                 } else {
1000                     format!("{}{}\n{}", mla, comment, mlb)
1001                 };
1002                 Some(format!(
1003                     "{}{}{}{}",
1004                     first_group_str,
1005                     comment,
1006                     shape.indent.to_string(context.config),
1007                     rest_str
1008                 ))
1009             } else {
1010                 combine_strs_with_missing_comments(
1011                     context,
1012                     &first_group_str,
1013                     &rest_str,
1014                     missing_span,
1015                     shape,
1016                     false,
1017                 )
1018             }
1019         }
1020     }
1021 }
1022
1023 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1024 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1025     let mut result = String::with_capacity(128);
1026     result.push_str("#[derive(");
1027     // 11 = `#[derive()]`
1028     let initial_budget = shape.width.checked_sub(11)?;
1029     let mut budget = initial_budget;
1030     let num = derive_args.len();
1031     for (i, a) in derive_args.iter().enumerate() {
1032         // 2 = `, ` or `)]`
1033         let width = a.len() + 2;
1034         if width > budget {
1035             if i > 0 {
1036                 // Remove trailing whitespace.
1037                 result.pop();
1038             }
1039             result.push('\n');
1040             // 9 = `#[derive(`
1041             result.push_str(&(shape.indent + 9).to_string(context.config));
1042             budget = initial_budget;
1043         } else {
1044             budget = budget.checked_sub(width).unwrap_or(0);
1045         }
1046         result.push_str(a);
1047         if i != num - 1 {
1048             result.push_str(", ")
1049         }
1050     }
1051     result.push_str(")]");
1052     Some(result)
1053 }
1054
1055 fn is_derive(attr: &ast::Attribute) -> bool {
1056     attr.check_name("derive")
1057 }
1058
1059 /// Returns the arguments of `#[derive(...)]`.
1060 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1061     attr.meta_item_list().map(|meta_item_list| {
1062         meta_item_list
1063             .iter()
1064             .map(|nested_meta_item| context.snippet(nested_meta_item.span))
1065             .collect()
1066     })
1067 }
1068
1069 // Rewrite `extern crate foo;` WITHOUT attributes.
1070 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1071     assert!(is_extern_crate(item));
1072     let new_str = context.snippet(item.span);
1073     Some(if contains_comment(new_str) {
1074         new_str.to_owned()
1075     } else {
1076         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1077         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1078     })
1079 }
1080
1081 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1082     match stmt.node {
1083         ast::StmtKind::Local(ref local) => &local.attrs,
1084         ast::StmtKind::Item(ref item) => &item.attrs,
1085         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1086         ast::StmtKind::Mac(ref mac) => &mac.2,
1087     }
1088 }