src/visitor.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::cmp;
  12
  13 use strings::string_buffer::StringBuffer;
  14 use syntax::{ast, visit};
  15 use syntax::attr::HasAttrs;
  16 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  17 use syntax::parse::ParseSess;
  18
  19 use expr::rewrite_literal;
  20 use spanned::Spanned;
  21 use codemap::{LineRangeUtils, SpanUtils};
  22 use comment::{combine_strs_with_missing_comments, contains_comment, remove_trailing_white_spaces,
  23               CodeCharKind, CommentCodeSlices, FindUncommented};
  24 use comment::rewrite_comment;
  25 use config::{BraceStyle, Config};
  26 use items::{format_impl, format_trait, rewrite_associated_impl_type, rewrite_associated_type,
  27             rewrite_type_alias, FnSig, StaticParts, StructParts};
  28 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  29             SeparatorTactic};
  30 use macros::{rewrite_macro, MacroPosition};
  31 use regex::Regex;
  32 use rewrite::{Rewrite, RewriteContext};
  33 use shape::{Indent, Shape};
  34 use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  35
  36 fn is_use_item(item: &ast::Item) -> bool {
  37     match item.node {
  38         ast::ItemKind::Use(_) => true,
  39         _ => false,
  40     }
  41 }
  42
  43 fn is_extern_crate(item: &ast::Item) -> bool {
  44     match item.node {
  45         ast::ItemKind::ExternCrate(..) => true,
  46         _ => false,
  47     }
  48 }
  49
  50 /// Creates a string slice corresponding to the specified span.
  51 pub struct SnippetProvider<'a> {
  52     /// A pointer to the content of the file we are formatting.
  53     big_snippet: &'a str,
  54     /// A position of the start of `big_snippet`, used as an offset.
  55     start_pos: usize,
  56 }
  57
  58 impl<'a> SnippetProvider<'a> {
  59     pub fn span_to_snippet(&self, span: Span) -> Option<&str> {
  60         let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
  61         let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
  62         Some(&self.big_snippet[start_index..end_index])
  63     }
  64
  65     pub fn new(start_pos: BytePos, big_snippet: &'a str) -> Self {
  66         let start_pos = start_pos.to_usize();
  67         SnippetProvider {
  68             big_snippet,
  69             start_pos,
  70         }
  71     }
  72 }
  73
  74 pub struct FmtVisitor<'a> {
  75     pub parse_session: &'a ParseSess,
  76     pub codemap: &'a CodeMap,
  77     pub buffer: StringBuffer,
  78     pub last_pos: BytePos,
  79     // FIXME: use an RAII util or closure for indenting
  80     pub block_indent: Indent,
  81     pub config: &'a Config,
  82     pub is_if_else_block: bool,
  83     pub snippet_provider: &'a SnippetProvider<'a>,
  84     pub line_number: usize,
  85     pub skipped_range: Vec<(usize, usize)>,
  86 }
  87
  88 impl<'b, 'a: 'b> FmtVisitor<'a> {
  89     pub fn shape(&self) -> Shape {
  90         Shape::indented(self.block_indent, self.config)
  91     }
  92
  93     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  94         debug!(
  95             "visit_stmt: {:?} {:?}",
  96             self.codemap.lookup_char_pos(stmt.span.lo()),
  97             self.codemap.lookup_char_pos(stmt.span.hi())
  98         );
  99
 100         match stmt.node {
 101             ast::StmtKind::Item(ref item) => {
 102                 self.visit_item(item);
 103             }
 104             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 105                 if contains_skip(get_attrs_from_stmt(stmt)) {
 106                     self.push_skipped_with_span(stmt.span());
 107                 } else {
 108                     let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 109                     self.push_rewrite(stmt.span(), rewrite)
 110                 }
 111             }
 112             ast::StmtKind::Mac(ref mac) => {
 113                 let (ref mac, _macro_style, ref attrs) = **mac;
 114                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 115                     self.push_skipped_with_span(stmt.span());
 116                 } else {
 117                     self.visit_mac(mac, None, MacroPosition::Statement);
 118                 }
 119                 self.format_missing(stmt.span.hi());
 120             }
 121         }
 122     }
 123
 124     pub fn visit_block(
 125         &mut self,
 126         b: &ast::Block,
 127         inner_attrs: Option<&[ast::Attribute]>,
 128         has_braces: bool,
 129     ) {
 130         debug!(
 131             "visit_block: {:?} {:?}",
 132             self.codemap.lookup_char_pos(b.span.lo()),
 133             self.codemap.lookup_char_pos(b.span.hi())
 134         );
 135
 136         // Check if this block has braces.
 137         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 138
 139         self.last_pos = self.last_pos + brace_compensation;
 140         self.block_indent = self.block_indent.block_indent(self.config);
 141         self.push_str("{");
 142
 143         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 144             if let Some(first_stmt) = b.stmts.first() {
 145                 let attr_lo = inner_attrs
 146                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 147                     .or_else(|| {
 148                         // Attributes for an item in a statement position
 149                         // do not belong to the statement. (rust-lang/rust#34459)
 150                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 151                             item.attrs.first()
 152                         } else {
 153                             first_stmt.attrs().first()
 154                         }.and_then(|attr| {
 155                             // Some stmts can have embedded attributes.
 156                             // e.g. `match { #![attr] ... }`
 157                             let attr_lo = attr.span.lo();
 158                             if attr_lo < first_stmt.span.lo() {
 159                                 Some(attr_lo)
 160                             } else {
 161                                 None
 162                             }
 163                         })
 164                     });
 165
 166                 let snippet = self.snippet(mk_sp(
 167                     self.last_pos,
 168                     attr_lo.unwrap_or(first_stmt.span.lo()),
 169                 ));
 170                 let len = CommentCodeSlices::new(&snippet)
 171                     .nth(0)
 172                     .and_then(|(kind, _, s)| {
 173                         if kind == CodeCharKind::Normal {
 174                             s.rfind('\n')
 175                         } else {
 176                             None
 177                         }
 178                     });
 179                 if let Some(len) = len {
 180                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 181                 }
 182             }
 183         }
 184
 185         // Format inner attributes if available.
 186         let skip_rewrite = if let Some(attrs) = inner_attrs {
 187             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 188         } else {
 189             false
 190         };
 191
 192         if skip_rewrite {
 193             self.push_rewrite(b.span, None);
 194             self.close_block(false);
 195             self.last_pos = source!(self, b.span).hi();
 196             return;
 197         }
 198
 199         self.walk_block_stmts(b);
 200
 201         if !b.stmts.is_empty() {
 202             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 203                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 204                     self.push_str(";");
 205                 }
 206             }
 207         }
 208
 209         let mut remove_len = BytePos(0);
 210         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 211             if let Some(stmt) = b.stmts.last() {
 212                 let snippet = self.snippet(mk_sp(
 213                     stmt.span.hi(),
 214                     source!(self, b.span).hi() - brace_compensation,
 215                 ));
 216                 let len = CommentCodeSlices::new(&snippet)
 217                     .last()
 218                     .and_then(|(kind, _, s)| {
 219                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 220                             Some(s.len())
 221                         } else {
 222                             None
 223                         }
 224                     });
 225                 if let Some(len) = len {
 226                     remove_len = BytePos::from_usize(len);
 227                 }
 228             }
 229         }
 230
 231         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 232             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 233             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 234             snippet.contains("//") || snippet.contains("/*")
 235         };
 236         // FIXME: we should compress any newlines here to just one
 237         if unindent_comment {
 238             self.block_indent = self.block_indent.block_unindent(self.config);
 239         }
 240         self.format_missing_with_indent(
 241             source!(self, b.span).hi() - brace_compensation - remove_len,
 242         );
 243         if unindent_comment {
 244             self.block_indent = self.block_indent.block_indent(self.config);
 245         }
 246         self.close_block(unindent_comment);
 247         self.last_pos = source!(self, b.span).hi();
 248     }
 249
 250     // FIXME: this is a terrible hack to indent the comments between the last
 251     // item in the block and the closing brace to the block's level.
 252     // The closing brace itself, however, should be indented at a shallower
 253     // level.
 254     fn close_block(&mut self, unindent_comment: bool) {
 255         let total_len = self.buffer.len;
 256         let chars_too_many = if unindent_comment {
 257             0
 258         } else if self.config.hard_tabs() {
 259             1
 260         } else {
 261             self.config.tab_spaces()
 262         };
 263         self.buffer.truncate(total_len - chars_too_many);
 264         self.push_str("}");
 265         self.block_indent = self.block_indent.block_unindent(self.config);
 266     }
 267
 268     // Note that this only gets called for function definitions. Required methods
 269     // on traits do not get handled here.
 270     fn visit_fn(
 271         &mut self,
 272         fk: visit::FnKind,
 273         generics: &ast::Generics,
 274         fd: &ast::FnDecl,
 275         s: Span,
 276         defaultness: ast::Defaultness,
 277         inner_attrs: Option<&[ast::Attribute]>,
 278     ) {
 279         let indent = self.block_indent;
 280         let block;
 281         let rewrite = match fk {
 282             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 283                 block = b;
 284                 self.rewrite_fn(
 285                     indent,
 286                     ident,
 287                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 288                     mk_sp(s.lo(), b.span.lo()),
 289                     b,
 290                 )
 291             }
 292             visit::FnKind::Closure(_) => unreachable!(),
 293         };
 294
 295         if let Some(fn_str) = rewrite {
 296             self.format_missing_with_indent(source!(self, s).lo());
 297             self.push_str(&fn_str);
 298             if let Some(c) = fn_str.chars().last() {
 299                 if c == '}' {
 300                     self.last_pos = source!(self, block.span).hi();
 301                     return;
 302                 }
 303             }
 304         } else {
 305             self.format_missing(source!(self, block.span).lo());
 306         }
 307
 308         self.last_pos = source!(self, block.span).lo();
 309         self.visit_block(block, inner_attrs, true)
 310     }
 311
 312     pub fn visit_item(&mut self, item: &ast::Item) {
 313         skip_out_of_file_lines_range_visitor!(self, item.span);
 314
 315         // This is where we bail out if there is a skip attribute. This is only
 316         // complex in the module case. It is complex because the module could be
 317         // in a separate file and there might be attributes in both files, but
 318         // the AST lumps them all together.
 319         let filtered_attrs;
 320         let mut attrs = &item.attrs;
 321         match item.node {
 322             ast::ItemKind::Mod(ref m) => {
 323                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 324                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 325                 if outer_file.name == inner_file.name {
 326                     // Module is inline, in this case we treat modules like any
 327                     // other item.
 328                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 329                         self.push_skipped_with_span(item.span());
 330                         return;
 331                     }
 332                 } else if contains_skip(&item.attrs) {
 333                     // Module is not inline, but should be skipped.
 334                     return;
 335                 } else {
 336                     // Module is not inline and should not be skipped. We want
 337                     // to process only the attributes in the current file.
 338                     filtered_attrs = item.attrs
 339                         .iter()
 340                         .filter_map(|a| {
 341                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 342                             if attr_file.name == outer_file.name {
 343                                 Some(a.clone())
 344                             } else {
 345                                 None
 346                             }
 347                         })
 348                         .collect::<Vec<_>>();
 349                     // Assert because if we should skip it should be caught by
 350                     // the above case.
 351                     assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 352                     attrs = &filtered_attrs;
 353                 }
 354             }
 355             _ => {
 356                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 357                     self.push_skipped_with_span(item.span());
 358                     return;
 359                 }
 360             }
 361         }
 362
 363         match item.node {
 364             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 365             ast::ItemKind::Impl(..) => {
 366                 let snippet = self.snippet(item.span);
 367                 let where_span_end = snippet
 368                     .find_uncommented("{")
 369                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 370                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 371                 self.push_rewrite(item.span, rw);
 372             }
 373             ast::ItemKind::Trait(..) => {
 374                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 375                 self.push_rewrite(item.span, rw);
 376             }
 377             ast::ItemKind::ExternCrate(_) => {
 378                 let rw = rewrite_extern_crate(&self.get_context(), item);
 379                 self.push_rewrite(item.span, rw);
 380             }
 381             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 382                 self.visit_struct(&StructParts::from_item(item));
 383             }
 384             ast::ItemKind::Enum(ref def, ref generics) => {
 385                 self.format_missing_with_indent(source!(self, item.span).lo());
 386                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 387                 self.last_pos = source!(self, item.span).hi();
 388             }
 389             ast::ItemKind::Mod(ref module) => {
 390                 self.format_missing_with_indent(source!(self, item.span).lo());
 391                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 392             }
 393             ast::ItemKind::Mac(ref mac) => {
 394                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 395             }
 396             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 397                 self.format_missing_with_indent(source!(self, item.span).lo());
 398                 self.format_foreign_mod(foreign_mod, item.span);
 399             }
 400             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 401                 self.visit_static(&StaticParts::from_item(item));
 402             }
 403             ast::ItemKind::AutoImpl(..) => {
 404                 // FIXME(#78): format impl definitions.
 405             }
 406             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 407                 self.visit_fn(
 408                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 409                     generics,
 410                     decl,
 411                     item.span,
 412                     ast::Defaultness::Final,
 413                     Some(&item.attrs),
 414                 )
 415             }
 416             ast::ItemKind::Ty(ref ty, ref generics) => {
 417                 let rewrite = rewrite_type_alias(
 418                     &self.get_context(),
 419                     self.block_indent,
 420                     item.ident,
 421                     ty,
 422                     generics,
 423                     &item.vis,
 424                     item.span,
 425                 );
 426                 self.push_rewrite(item.span, rewrite);
 427             }
 428             ast::ItemKind::GlobalAsm(..) => {
 429                 let snippet = Some(self.snippet(item.span).to_owned());
 430                 self.push_rewrite(item.span, snippet);
 431             }
 432             ast::ItemKind::MacroDef(..) => {
 433                 // FIXME(#1539): macros 2.0
 434                 let mac_snippet = Some(remove_trailing_white_spaces(&self.snippet(item.span)));
 435                 self.push_rewrite(item.span, mac_snippet);
 436             }
 437         }
 438     }
 439
 440     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 441         skip_out_of_file_lines_range_visitor!(self, ti.span);
 442
 443         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 444             self.push_skipped_with_span(ti.span());
 445             return;
 446         }
 447
 448         match ti.node {
 449             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 450             ast::TraitItemKind::Method(ref sig, None) => {
 451                 let indent = self.block_indent;
 452                 let rewrite =
 453                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 454                 self.push_rewrite(ti.span, rewrite);
 455             }
 456             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 457                 self.visit_fn(
 458                     visit::FnKind::Method(ti.ident, sig, None, body),
 459                     &ti.generics,
 460                     &sig.decl,
 461                     ti.span,
 462                     ast::Defaultness::Final,
 463                     Some(&ti.attrs),
 464                 );
 465             }
 466             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 467                 let rewrite = rewrite_associated_type(
 468                     ti.ident,
 469                     type_default.as_ref(),
 470                     Some(type_param_bounds),
 471                     &self.get_context(),
 472                     self.block_indent,
 473                 );
 474                 self.push_rewrite(ti.span, rewrite);
 475             }
 476             ast::TraitItemKind::Macro(ref mac) => {
 477                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 478             }
 479         }
 480     }
 481
 482     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 483         skip_out_of_file_lines_range_visitor!(self, ii.span);
 484
 485         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 486             self.push_skipped_with_span(ii.span());
 487             return;
 488         }
 489
 490         match ii.node {
 491             ast::ImplItemKind::Method(ref sig, ref body) => {
 492                 self.visit_fn(
 493                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 494                     &ii.generics,
 495                     &sig.decl,
 496                     ii.span,
 497                     ii.defaultness,
 498                     Some(&ii.attrs),
 499                 );
 500             }
 501             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 502             ast::ImplItemKind::Type(ref ty) => {
 503                 let rewrite = rewrite_associated_impl_type(
 504                     ii.ident,
 505                     ii.defaultness,
 506                     Some(ty),
 507                     None,
 508                     &self.get_context(),
 509                     self.block_indent,
 510                 );
 511                 self.push_rewrite(ii.span, rewrite);
 512             }
 513             ast::ImplItemKind::Macro(ref mac) => {
 514                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 515             }
 516         }
 517     }
 518
 519     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 520         skip_out_of_file_lines_range_visitor!(self, mac.span);
 521
 522         // 1 = ;
 523         let shape = self.shape().sub_width(1).unwrap();
 524         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 525         self.push_rewrite(mac.span, rewrite);
 526     }
 527
 528     pub fn push_str(&mut self, s: &str) {
 529         self.line_number += count_newlines(s);
 530         self.buffer.push_str(s);
 531     }
 532
 533     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 534         if let Some(ref s) = rewrite {
 535             self.push_str(s);
 536         } else {
 537             let snippet = self.snippet(span);
 538             self.push_str(snippet);
 539         }
 540         self.last_pos = source!(self, span).hi();
 541     }
 542
 543     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 544         self.format_missing_with_indent(source!(self, span).lo());
 545         self.push_rewrite_inner(span, rewrite);
 546     }
 547
 548     pub fn push_skipped_with_span(&mut self, span: Span) {
 549         self.format_missing_with_indent(source!(self, span).lo());
 550         let lo = self.line_number + 1;
 551         self.push_rewrite_inner(span, None);
 552         let hi = self.line_number + 1;
 553         self.skipped_range.push((lo, hi));
 554     }
 555
 556     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 557         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 558     }
 559
 560     pub fn from_codemap(
 561         parse_session: &'a ParseSess,
 562         config: &'a Config,
 563         snippet_provider: &'a SnippetProvider,
 564     ) -> FmtVisitor<'a> {
 565         FmtVisitor {
 566             parse_session: parse_session,
 567             codemap: parse_session.codemap(),
 568             buffer: StringBuffer::new(),
 569             last_pos: BytePos(0),
 570             block_indent: Indent::empty(),
 571             config: config,
 572             is_if_else_block: false,
 573             snippet_provider: snippet_provider,
 574             line_number: 0,
 575             skipped_range: vec![],
 576         }
 577     }
 578
 579     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 580         self.snippet_provider.span_to_snippet(span)
 581     }
 582
 583     pub fn snippet(&'b self, span: Span) -> &'a str {
 584         self.opt_snippet(span).unwrap()
 585     }
 586
 587     // Returns true if we should skip the following item.
 588     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 589         if contains_skip(attrs) {
 590             return true;
 591         }
 592
 593         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 594         if attrs.is_empty() {
 595             return false;
 596         }
 597
 598         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 599         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 600         self.push_rewrite(span, rewrite);
 601
 602         false
 603     }
 604
 605     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 606     where
 607         F: Fn(&ast::Item) -> bool,
 608     {
 609         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 610         let item_length = items_left
 611             .iter()
 612             .take_while(|ppi| {
 613                 is_item(&***ppi) && (!in_group || {
 614                     let current = self.codemap.lookup_line_range(ppi.span());
 615                     let in_same_group = current.lo < last.hi + 2;
 616                     last = current;
 617                     in_same_group
 618                 })
 619             })
 620             .count();
 621         let items = &items_left[..item_length];
 622
 623         let at_least_one_in_file_lines = items
 624             .iter()
 625             .any(|item| !out_of_file_lines_range!(self, item.span));
 626
 627         if at_least_one_in_file_lines {
 628             self.format_imports(items);
 629         } else {
 630             for item in items {
 631                 self.push_rewrite(item.span, None);
 632             }
 633         }
 634
 635         item_length
 636     }
 637
 638     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 639         while !items_left.is_empty() {
 640             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 641             // to be potentially reordered within `format_imports`. Otherwise, just format the
 642             // next item for output.
 643             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 644                 let used_items_len = self.reorder_items(
 645                     items_left,
 646                     &is_use_item,
 647                     self.config.reorder_imports_in_group(),
 648                 );
 649                 let (_, rest) = items_left.split_at(used_items_len);
 650                 items_left = rest;
 651             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 652                 let used_items_len = self.reorder_items(
 653                     items_left,
 654                     &is_extern_crate,
 655                     self.config.reorder_extern_crates_in_group(),
 656                 );
 657                 let (_, rest) = items_left.split_at(used_items_len);
 658                 items_left = rest;
 659             } else {
 660                 // `unwrap()` is safe here because we know `items_left`
 661                 // has elements from the loop condition
 662                 let (item, rest) = items_left.split_first().unwrap();
 663                 self.visit_item(item);
 664                 items_left = rest;
 665             }
 666         }
 667     }
 668
 669     fn walk_mod_items(&mut self, m: &ast::Mod) {
 670         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 671     }
 672
 673     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 674         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 675             match stmt.node {
 676                 ast::StmtKind::Item(ref item) => Some(&**item),
 677                 _ => None,
 678             }
 679         }
 680
 681         if stmts.is_empty() {
 682             return;
 683         }
 684
 685         // Extract leading `use ...;`.
 686         let items: Vec<_> = stmts
 687             .iter()
 688             .take_while(|stmt| to_stmt_item(stmt).is_some())
 689             .filter_map(|stmt| to_stmt_item(stmt))
 690             .take_while(|item| is_use_item(item))
 691             .collect();
 692
 693         if items.is_empty() {
 694             self.visit_stmt(&stmts[0]);
 695             self.walk_stmts(&stmts[1..]);
 696         } else {
 697             self.walk_items(&items);
 698             self.walk_stmts(&stmts[items.len()..]);
 699         }
 700     }
 701
 702     fn walk_block_stmts(&mut self, b: &ast::Block) {
 703         self.walk_stmts(&b.stmts)
 704     }
 705
 706     fn format_mod(
 707         &mut self,
 708         m: &ast::Mod,
 709         vis: &ast::Visibility,
 710         s: Span,
 711         ident: ast::Ident,
 712         attrs: &[ast::Attribute],
 713     ) {
 714         // Decide whether this is an inline mod or an external mod.
 715         let local_file_name = self.codemap.span_to_filename(s);
 716         let inner_span = source!(self, m.inner);
 717         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 718             && local_file_name == self.codemap.span_to_filename(inner_span);
 719
 720         self.push_str(&*utils::format_visibility(vis));
 721         self.push_str("mod ");
 722         self.push_str(&ident.to_string());
 723
 724         if is_internal {
 725             match self.config.brace_style() {
 726                 BraceStyle::AlwaysNextLine => {
 727                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 728                     self.push_str(&sep_str);
 729                 }
 730                 _ => self.push_str(" {"),
 731             }
 732             // Hackery to account for the closing }.
 733             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 734             let body_snippet =
 735                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 736             let body_snippet = body_snippet.trim();
 737             if body_snippet.is_empty() {
 738                 self.push_str("}");
 739             } else {
 740                 self.last_pos = mod_lo;
 741                 self.block_indent = self.block_indent.block_indent(self.config);
 742                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 743                 self.walk_mod_items(m);
 744                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 745                 self.close_block(false);
 746             }
 747             self.last_pos = source!(self, m.inner).hi();
 748         } else {
 749             self.push_str(";");
 750             self.last_pos = source!(self, s).hi();
 751         }
 752     }
 753
 754     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 755         self.block_indent = Indent::empty();
 756         self.walk_mod_items(m);
 757         self.format_missing_with_indent(filemap.end_pos);
 758     }
 759
 760     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 761         while let Some(pos) = self.codemap
 762             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 763         {
 764             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 765                 if snippet.trim().is_empty() {
 766                     self.last_pos = pos;
 767                 } else {
 768                     return;
 769                 }
 770             }
 771         }
 772     }
 773
 774     pub fn get_context(&self) -> RewriteContext {
 775         RewriteContext {
 776             parse_session: self.parse_session,
 777             codemap: self.codemap,
 778             config: self.config,
 779             inside_macro: false,
 780             use_block: false,
 781             is_if_else_block: false,
 782             force_one_line_chain: false,
 783             snippet_provider: &self.snippet_provider,
 784         }
 785     }
 786 }
 787
 788 impl Rewrite for ast::NestedMetaItem {
 789     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 790         match self.node {
 791             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 792             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 793         }
 794     }
 795 }
 796
 797 impl Rewrite for ast::MetaItem {
 798     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 799         Some(match self.node {
 800             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 801             ast::MetaItemKind::List(ref list) => {
 802                 let name = self.name.as_str();
 803                 // 1 = `(`, 2 = `]` and `)`
 804                 let item_shape = shape
 805                     .visual_indent(0)
 806                     .shrink_left(name.len() + 1)
 807                     .and_then(|s| s.sub_width(2))?;
 808                 let items = itemize_list(
 809                     context.codemap,
 810                     list.iter(),
 811                     ")",
 812                     ",",
 813                     |nested_meta_item| nested_meta_item.span.lo(),
 814                     |nested_meta_item| nested_meta_item.span.hi(),
 815                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 816                     self.span.lo(),
 817                     self.span.hi(),
 818                     false,
 819                 );
 820                 let item_vec = items.collect::<Vec<_>>();
 821                 let fmt = ListFormatting {
 822                     tactic: DefinitiveListTactic::Mixed,
 823                     separator: ",",
 824                     trailing_separator: SeparatorTactic::Never,
 825                     separator_place: SeparatorPlace::Back,
 826                     shape: item_shape,
 827                     ends_with_newline: false,
 828                     preserve_newline: false,
 829                     config: context.config,
 830                 };
 831                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 832             }
 833             ast::MetaItemKind::NameValue(ref literal) => {
 834                 let name = self.name.as_str();
 835                 // 3 = ` = `
 836                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 837                 let value = rewrite_literal(context, literal, lit_shape)?;
 838                 format!("{} = {}", name, value)
 839             }
 840         })
 841     }
 842 }
 843
 844 impl Rewrite for ast::Attribute {
 845     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 846         let prefix = match self.style {
 847             ast::AttrStyle::Inner => "#!",
 848             ast::AttrStyle::Outer => "#",
 849         };
 850         let snippet = context.snippet(self.span);
 851         if self.is_sugared_doc {
 852             let doc_shape = Shape {
 853                 width: cmp::min(shape.width, context.config.comment_width())
 854                     .checked_sub(shape.indent.width())
 855                     .unwrap_or(0),
 856                 ..shape
 857             };
 858             rewrite_comment(snippet, false, doc_shape, context.config)
 859         } else {
 860             if contains_comment(snippet) {
 861                 return Some(snippet.to_owned());
 862             }
 863             // 1 = `[`
 864             let shape = shape.offset_left(prefix.len() + 1)?;
 865             self.meta()?
 866                 .rewrite(context, shape)
 867                 .map(|rw| format!("{}[{}]", prefix, rw))
 868         }
 869     }
 870 }
 871
 872 /// Returns the first group of attributes that fills the given predicate.
 873 /// We consider two doc comments are in different group if they are separated by normal comments.
 874 fn take_while_with_pred<'a, P>(
 875     context: &RewriteContext,
 876     attrs: &'a [ast::Attribute],
 877     pred: P,
 878 ) -> &'a [ast::Attribute]
 879 where
 880     P: Fn(&ast::Attribute) -> bool,
 881 {
 882     let mut last_index = 0;
 883     let mut iter = attrs.iter().enumerate().peekable();
 884     while let Some((i, attr)) = iter.next() {
 885         if !pred(attr) {
 886             break;
 887         }
 888         if let Some(&(_, next_attr)) = iter.peek() {
 889             // Extract comments between two attributes.
 890             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 891             let snippet = context.snippet(span_between_attr);
 892             if count_newlines(&snippet) >= 2 || snippet.contains('/') {
 893                 break;
 894             }
 895         }
 896         last_index = i;
 897     }
 898     if last_index == 0 {
 899         &[]
 900     } else {
 901         &attrs[..last_index + 1]
 902     }
 903 }
 904
 905 fn rewrite_first_group_attrs(
 906     context: &RewriteContext,
 907     attrs: &[ast::Attribute],
 908     shape: Shape,
 909 ) -> Option<(usize, String)> {
 910     if attrs.is_empty() {
 911         return Some((0, String::new()));
 912     }
 913     // Rewrite doc comments
 914     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 915     if !sugared_docs.is_empty() {
 916         let snippet = sugared_docs
 917             .iter()
 918             .map(|a| context.snippet(a.span))
 919             .collect::<Vec<_>>()
 920             .join("\n");
 921         return Some((
 922             sugared_docs.len(),
 923             rewrite_comment(&snippet, false, shape, context.config)?,
 924         ));
 925     }
 926     // Rewrite `#[derive(..)]`s.
 927     if context.config.merge_derives() {
 928         let derives = take_while_with_pred(context, attrs, is_derive);
 929         if !derives.is_empty() {
 930             let mut derive_args = vec![];
 931             for derive in derives {
 932                 derive_args.append(&mut get_derive_args(context, derive)?);
 933             }
 934             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 935         }
 936     }
 937     // Rewrite the first attribute.
 938     Some((1, attrs[0].rewrite(context, shape)?))
 939 }
 940
 941 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 942     // Look at before and after comment and see if there are any empty lines.
 943     let comment_begin = comment.chars().position(|c| c == '/');
 944     let len = comment_begin.unwrap_or_else(|| comment.len());
 945     let mlb = count_newlines(&comment[..len]) > 1;
 946     let mla = if comment_begin.is_none() {
 947         mlb
 948     } else {
 949         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 950         let len = comment_end.unwrap();
 951         comment
 952             .chars()
 953             .rev()
 954             .take(len)
 955             .filter(|c| *c == '\n')
 956             .count() > 1
 957     };
 958     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 959 }
 960
 961 impl<'a> Rewrite for [ast::Attribute] {
 962     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 963         if self.is_empty() {
 964             return Some(String::new());
 965         }
 966         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 967         if self.len() == 1 || first_group_len == self.len() {
 968             Some(first_group_str)
 969         } else {
 970             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 971             let missing_span = mk_sp(
 972                 self[first_group_len - 1].span.hi(),
 973                 self[first_group_len].span.lo(),
 974             );
 975             // Preserve an empty line before/after doc comments.
 976             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 977                 let snippet = context.snippet(missing_span);
 978                 let (mla, mlb) = has_newlines_before_after_comment(&snippet);
 979                 let comment = ::comment::recover_missing_comment_in_span(
 980                     missing_span,
 981                     shape.with_max_width(context.config),
 982                     context,
 983                     0,
 984                 )?;
 985                 let comment = if comment.is_empty() {
 986                     format!("\n{}", mlb)
 987                 } else {
 988                     format!("{}{}\n{}", mla, comment, mlb)
 989                 };
 990                 Some(format!(
 991                     "{}{}{}{}",
 992                     first_group_str,
 993                     comment,
 994                     shape.indent.to_string(context.config),
 995                     rest_str
 996                 ))
 997             } else {
 998                 combine_strs_with_missing_comments(
 999                     context,
1000                     &first_group_str,
1001                     &rest_str,
1002                     missing_span,
1003                     shape,
1004                     false,
1005                 )
1006             }
1007         }
1008     }
1009 }
1010
1011 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1012 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1013     let mut result = String::with_capacity(128);
1014     result.push_str("#[derive(");
1015     // 11 = `#[derive()]`
1016     let initial_budget = shape.width.checked_sub(11)?;
1017     let mut budget = initial_budget;
1018     let num = derive_args.len();
1019     for (i, a) in derive_args.iter().enumerate() {
1020         // 2 = `, ` or `)]`
1021         let width = a.len() + 2;
1022         if width > budget {
1023             if i > 0 {
1024                 // Remove trailing whitespace.
1025                 result.pop();
1026             }
1027             result.push('\n');
1028             // 9 = `#[derive(`
1029             result.push_str(&(shape.indent + 9).to_string(context.config));
1030             budget = initial_budget;
1031         } else {
1032             budget = budget.checked_sub(width).unwrap_or(0);
1033         }
1034         result.push_str(a);
1035         if i != num - 1 {
1036             result.push_str(", ")
1037         }
1038     }
1039     result.push_str(")]");
1040     Some(result)
1041 }
1042
1043 fn is_derive(attr: &ast::Attribute) -> bool {
1044     match attr.meta() {
1045         Some(meta_item) => match meta_item.node {
1046             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1047             _ => false,
1048         },
1049         _ => false,
1050     }
1051 }
1052
1053 /// Returns the arguments of `#[derive(...)]`.
1054 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1055     attr.meta().and_then(|meta_item| match meta_item.node {
1056         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1057             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1058             Some(
1059                 args.iter()
1060                     .map(|a| context.snippet(a.span))
1061                     .collect::<Vec<_>>(),
1062             )
1063         }
1064         _ => None,
1065     })
1066 }
1067
1068 // Rewrite `extern crate foo;` WITHOUT attributes.
1069 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1070     assert!(is_extern_crate(item));
1071     let new_str = context.snippet(item.span);
1072     Some(if contains_comment(&new_str) {
1073         new_str.to_owned()
1074     } else {
1075         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1076         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1077     })
1078 }
1079
1080 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1081     match stmt.node {
1082         ast::StmtKind::Local(ref local) => &local.attrs,
1083         ast::StmtKind::Item(ref item) => &item.attrs,
1084         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1085         ast::StmtKind::Mac(ref mac) => &mac.2,
1086     }
1087 }