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