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