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<'b, 'a: 'b> SnippetProvider<'a> {
  59     pub fn span_to_snippet(&'b self, span: Span) -> Option<&'a 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 }
  85
  86 impl<'b, 'a: 'b> FmtVisitor<'a> {
  87     pub fn shape(&self) -> Shape {
  88         Shape::indented(self.block_indent, self.config)
  89     }
  90
  91     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  92         debug!(
  93             "visit_stmt: {:?} {:?}",
  94             self.codemap.lookup_char_pos(stmt.span.lo()),
  95             self.codemap.lookup_char_pos(stmt.span.hi())
  96         );
  97
  98         match stmt.node {
  99             ast::StmtKind::Item(ref item) => {
 100                 self.visit_item(item);
 101             }
 102             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 103                 let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 104                 self.push_rewrite(stmt.span(), rewrite)
 105             }
 106             ast::StmtKind::Mac(ref mac) => {
 107                 let (ref mac, _macro_style, ref attrs) = **mac;
 108                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 109                     self.push_rewrite(stmt.span(), None);
 110                 } else {
 111                     self.visit_mac(mac, None, MacroPosition::Statement);
 112                 }
 113                 self.format_missing(stmt.span.hi());
 114             }
 115         }
 116     }
 117
 118     pub fn visit_block(
 119         &mut self,
 120         b: &ast::Block,
 121         inner_attrs: Option<&[ast::Attribute]>,
 122         has_braces: bool,
 123     ) {
 124         debug!(
 125             "visit_block: {:?} {:?}",
 126             self.codemap.lookup_char_pos(b.span.lo()),
 127             self.codemap.lookup_char_pos(b.span.hi())
 128         );
 129
 130         // Check if this block has braces.
 131         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 132
 133         self.last_pos = self.last_pos + brace_compensation;
 134         self.block_indent = self.block_indent.block_indent(self.config);
 135         self.buffer.push_str("{");
 136
 137         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 138             if let Some(first_stmt) = b.stmts.first() {
 139                 let attr_lo = inner_attrs
 140                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 141                     .or_else(|| {
 142                         // Attributes for an item in a statement position
 143                         // do not belong to the statement. (rust-lang/rust#34459)
 144                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 145                             item.attrs.first()
 146                         } else {
 147                             first_stmt.attrs().first()
 148                         }.and_then(|attr| {
 149                             // Some stmts can have embedded attributes.
 150                             // e.g. `match { #![attr] ... }`
 151                             let attr_lo = attr.span.lo();
 152                             if attr_lo < first_stmt.span.lo() {
 153                                 Some(attr_lo)
 154                             } else {
 155                                 None
 156                             }
 157                         })
 158                     });
 159
 160                 let snippet = self.snippet(mk_sp(
 161                     self.last_pos,
 162                     attr_lo.unwrap_or(first_stmt.span.lo()),
 163                 ));
 164                 let len = CommentCodeSlices::new(&snippet)
 165                     .nth(0)
 166                     .and_then(|(kind, _, s)| {
 167                         if kind == CodeCharKind::Normal {
 168                             s.rfind('\n')
 169                         } else {
 170                             None
 171                         }
 172                     });
 173                 if let Some(len) = len {
 174                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 175                 }
 176             }
 177         }
 178
 179         // Format inner attributes if available.
 180         let skip_rewrite = if let Some(attrs) = inner_attrs {
 181             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 182         } else {
 183             false
 184         };
 185
 186         if skip_rewrite {
 187             self.push_rewrite(b.span, None);
 188             self.close_block(false);
 189             self.last_pos = source!(self, b.span).hi();
 190             return;
 191         }
 192
 193         self.walk_block_stmts(b);
 194
 195         if !b.stmts.is_empty() {
 196             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 197                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 198                     self.buffer.push_str(";");
 199                 }
 200             }
 201         }
 202
 203         let mut remove_len = BytePos(0);
 204         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 205             if let Some(stmt) = b.stmts.last() {
 206                 let snippet = self.snippet(mk_sp(
 207                     stmt.span.hi(),
 208                     source!(self, b.span).hi() - brace_compensation,
 209                 ));
 210                 let len = CommentCodeSlices::new(&snippet)
 211                     .last()
 212                     .and_then(|(kind, _, s)| {
 213                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 214                             Some(s.len())
 215                         } else {
 216                             None
 217                         }
 218                     });
 219                 if let Some(len) = len {
 220                     remove_len = BytePos::from_usize(len);
 221                 }
 222             }
 223         }
 224
 225         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 226             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 227             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 228             snippet.contains("//") || snippet.contains("/*")
 229         };
 230         // FIXME: we should compress any newlines here to just one
 231         if unindent_comment {
 232             self.block_indent = self.block_indent.block_unindent(self.config);
 233         }
 234         self.format_missing_with_indent(
 235             source!(self, b.span).hi() - brace_compensation - remove_len,
 236         );
 237         if unindent_comment {
 238             self.block_indent = self.block_indent.block_indent(self.config);
 239         }
 240         self.close_block(unindent_comment);
 241         self.last_pos = source!(self, b.span).hi();
 242     }
 243
 244     // FIXME: this is a terrible hack to indent the comments between the last
 245     // item in the block and the closing brace to the block's level.
 246     // The closing brace itself, however, should be indented at a shallower
 247     // level.
 248     fn close_block(&mut self, unindent_comment: bool) {
 249         let total_len = self.buffer.len;
 250         let chars_too_many = if unindent_comment {
 251             0
 252         } else if self.config.hard_tabs() {
 253             1
 254         } else {
 255             self.config.tab_spaces()
 256         };
 257         self.buffer.truncate(total_len - chars_too_many);
 258         self.buffer.push_str("}");
 259         self.block_indent = self.block_indent.block_unindent(self.config);
 260     }
 261
 262     // Note that this only gets called for function definitions. Required methods
 263     // on traits do not get handled here.
 264     fn visit_fn(
 265         &mut self,
 266         fk: visit::FnKind,
 267         generics: &ast::Generics,
 268         fd: &ast::FnDecl,
 269         s: Span,
 270         defaultness: ast::Defaultness,
 271         inner_attrs: Option<&[ast::Attribute]>,
 272     ) {
 273         let indent = self.block_indent;
 274         let block;
 275         let rewrite = match fk {
 276             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 277                 block = b;
 278                 self.rewrite_fn(
 279                     indent,
 280                     ident,
 281                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 282                     mk_sp(s.lo(), b.span.lo()),
 283                     b,
 284                 )
 285             }
 286             visit::FnKind::Closure(_) => unreachable!(),
 287         };
 288
 289         if let Some(fn_str) = rewrite {
 290             self.format_missing_with_indent(source!(self, s).lo());
 291             self.buffer.push_str(&fn_str);
 292             if let Some(c) = fn_str.chars().last() {
 293                 if c == '}' {
 294                     self.last_pos = source!(self, block.span).hi();
 295                     return;
 296                 }
 297             }
 298         } else {
 299             self.format_missing(source!(self, block.span).lo());
 300         }
 301
 302         self.last_pos = source!(self, block.span).lo();
 303         self.visit_block(block, inner_attrs, true)
 304     }
 305
 306     pub fn visit_item(&mut self, item: &ast::Item) {
 307         skip_out_of_file_lines_range_visitor!(self, item.span);
 308
 309         // This is where we bail out if there is a skip attribute. This is only
 310         // complex in the module case. It is complex because the module could be
 311         // in a separate file and there might be attributes in both files, but
 312         // the AST lumps them all together.
 313         let filtered_attrs;
 314         let mut attrs = &item.attrs;
 315         match item.node {
 316             ast::ItemKind::Mod(ref m) => {
 317                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 318                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 319                 if outer_file.name == inner_file.name {
 320                     // Module is inline, in this case we treat modules like any
 321                     // other item.
 322                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 323                         self.push_rewrite(item.span, None);
 324                         return;
 325                     }
 326                 } else if contains_skip(&item.attrs) {
 327                     // Module is not inline, but should be skipped.
 328                     return;
 329                 } else {
 330                     // Module is not inline and should not be skipped. We want
 331                     // to process only the attributes in the current file.
 332                     filtered_attrs = item.attrs
 333                         .iter()
 334                         .filter_map(|a| {
 335                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 336                             if attr_file.name == outer_file.name {
 337                                 Some(a.clone())
 338                             } else {
 339                                 None
 340                             }
 341                         })
 342                         .collect::<Vec<_>>();
 343                     // Assert because if we should skip it should be caught by
 344                     // the above case.
 345                     assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 346                     attrs = &filtered_attrs;
 347                 }
 348             }
 349             _ => {
 350                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 351                     self.push_rewrite(item.span, None);
 352                     return;
 353                 }
 354             }
 355         }
 356
 357         match item.node {
 358             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 359             ast::ItemKind::Impl(..) => {
 360                 let snippet = self.snippet(item.span);
 361                 let where_span_end = snippet
 362                     .find_uncommented("{")
 363                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 364                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 365                 self.push_rewrite(item.span, rw);
 366             }
 367             ast::ItemKind::Trait(..) => {
 368                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 369                 self.push_rewrite(item.span, rw);
 370             }
 371             ast::ItemKind::ExternCrate(_) => {
 372                 let rw = rewrite_extern_crate(&self.get_context(), item);
 373                 self.push_rewrite(item.span, rw);
 374             }
 375             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 376                 self.visit_struct(&StructParts::from_item(item));
 377             }
 378             ast::ItemKind::Enum(ref def, ref generics) => {
 379                 self.format_missing_with_indent(source!(self, item.span).lo());
 380                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 381                 self.last_pos = source!(self, item.span).hi();
 382             }
 383             ast::ItemKind::Mod(ref module) => {
 384                 self.format_missing_with_indent(source!(self, item.span).lo());
 385                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 386             }
 387             ast::ItemKind::Mac(ref mac) => {
 388                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 389             }
 390             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 391                 self.format_missing_with_indent(source!(self, item.span).lo());
 392                 self.format_foreign_mod(foreign_mod, item.span);
 393             }
 394             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 395                 self.visit_static(&StaticParts::from_item(item));
 396             }
 397             ast::ItemKind::AutoImpl(..) => {
 398                 // FIXME(#78): format impl definitions.
 399             }
 400             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 401                 self.visit_fn(
 402                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 403                     generics,
 404                     decl,
 405                     item.span,
 406                     ast::Defaultness::Final,
 407                     Some(&item.attrs),
 408                 )
 409             }
 410             ast::ItemKind::Ty(ref ty, ref generics) => {
 411                 let rewrite = rewrite_type_alias(
 412                     &self.get_context(),
 413                     self.block_indent,
 414                     item.ident,
 415                     ty,
 416                     generics,
 417                     &item.vis,
 418                     item.span,
 419                 );
 420                 self.push_rewrite(item.span, rewrite);
 421             }
 422             ast::ItemKind::GlobalAsm(..) => {
 423                 let snippet = Some(self.snippet(item.span).into());
 424                 self.push_rewrite(item.span, snippet);
 425             }
 426             ast::ItemKind::MacroDef(..) => {
 427                 // FIXME(#1539): macros 2.0
 428                 let mac_snippet = Some(remove_trailing_white_spaces(&self.snippet(item.span)));
 429                 self.push_rewrite(item.span, mac_snippet);
 430             }
 431         }
 432     }
 433
 434     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 435         skip_out_of_file_lines_range_visitor!(self, ti.span);
 436
 437         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 438             self.push_rewrite(ti.span, None);
 439             return;
 440         }
 441
 442         match ti.node {
 443             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 444             ast::TraitItemKind::Method(ref sig, None) => {
 445                 let indent = self.block_indent;
 446                 let rewrite =
 447                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 448                 self.push_rewrite(ti.span, rewrite);
 449             }
 450             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 451                 self.visit_fn(
 452                     visit::FnKind::Method(ti.ident, sig, None, body),
 453                     &ti.generics,
 454                     &sig.decl,
 455                     ti.span,
 456                     ast::Defaultness::Final,
 457                     Some(&ti.attrs),
 458                 );
 459             }
 460             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 461                 let rewrite = rewrite_associated_type(
 462                     ti.ident,
 463                     type_default.as_ref(),
 464                     Some(type_param_bounds),
 465                     &self.get_context(),
 466                     self.block_indent,
 467                 );
 468                 self.push_rewrite(ti.span, rewrite);
 469             }
 470             ast::TraitItemKind::Macro(ref mac) => {
 471                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 472             }
 473         }
 474     }
 475
 476     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 477         skip_out_of_file_lines_range_visitor!(self, ii.span);
 478
 479         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 480             self.push_rewrite(ii.span, None);
 481             return;
 482         }
 483
 484         match ii.node {
 485             ast::ImplItemKind::Method(ref sig, ref body) => {
 486                 self.visit_fn(
 487                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 488                     &ii.generics,
 489                     &sig.decl,
 490                     ii.span,
 491                     ii.defaultness,
 492                     Some(&ii.attrs),
 493                 );
 494             }
 495             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 496             ast::ImplItemKind::Type(ref ty) => {
 497                 let rewrite = rewrite_associated_impl_type(
 498                     ii.ident,
 499                     ii.defaultness,
 500                     Some(ty),
 501                     None,
 502                     &self.get_context(),
 503                     self.block_indent,
 504                 );
 505                 self.push_rewrite(ii.span, rewrite);
 506             }
 507             ast::ImplItemKind::Macro(ref mac) => {
 508                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 509             }
 510         }
 511     }
 512
 513     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 514         skip_out_of_file_lines_range_visitor!(self, mac.span);
 515
 516         // 1 = ;
 517         let shape = self.shape().sub_width(1).unwrap();
 518         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 519         self.push_rewrite(mac.span, rewrite);
 520     }
 521
 522     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 523         self.format_missing_with_indent(source!(self, span).lo());
 524         if let Some(ref s) = rewrite {
 525             self.buffer.push_str(s);
 526         } else {
 527             let snippet = self.snippet(span);
 528             self.buffer.push_str(snippet);
 529         }
 530         self.last_pos = source!(self, span).hi();
 531     }
 532
 533     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 534         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 535     }
 536
 537     pub fn from_codemap(
 538         parse_session: &'a ParseSess,
 539         config: &'a Config,
 540         snippet_provider: &'a SnippetProvider,
 541     ) -> FmtVisitor<'a> {
 542         FmtVisitor {
 543             parse_session: parse_session,
 544             codemap: parse_session.codemap(),
 545             buffer: StringBuffer::new(),
 546             last_pos: BytePos(0),
 547             block_indent: Indent::empty(),
 548             config: config,
 549             is_if_else_block: false,
 550             snippet_provider: snippet_provider,
 551         }
 552     }
 553
 554     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 555         self.snippet_provider.span_to_snippet(span)
 556     }
 557
 558     pub fn snippet(&'b self, span: Span) -> &'a str {
 559         self.opt_snippet(span).unwrap()
 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             snippet_provider: &self.snippet_provider,
 757         }
 758     }
 759 }
 760
 761 impl Rewrite for ast::NestedMetaItem {
 762     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 763         match self.node {
 764             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 765             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 766         }
 767     }
 768 }
 769
 770 impl Rewrite for ast::MetaItem {
 771     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 772         Some(match self.node {
 773             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 774             ast::MetaItemKind::List(ref list) => {
 775                 let name = self.name.as_str();
 776                 // 1 = `(`, 2 = `]` and `)`
 777                 let item_shape = shape
 778                     .visual_indent(0)
 779                     .shrink_left(name.len() + 1)
 780                     .and_then(|s| s.sub_width(2))?;
 781                 let items = itemize_list(
 782                     context.codemap,
 783                     list.iter(),
 784                     ")",
 785                     ",",
 786                     |nested_meta_item| nested_meta_item.span.lo(),
 787                     |nested_meta_item| nested_meta_item.span.hi(),
 788                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 789                     self.span.lo(),
 790                     self.span.hi(),
 791                     false,
 792                 );
 793                 let item_vec = items.collect::<Vec<_>>();
 794                 let fmt = ListFormatting {
 795                     tactic: DefinitiveListTactic::Mixed,
 796                     separator: ",",
 797                     trailing_separator: SeparatorTactic::Never,
 798                     separator_place: SeparatorPlace::Back,
 799                     shape: item_shape,
 800                     ends_with_newline: false,
 801                     preserve_newline: false,
 802                     config: context.config,
 803                 };
 804                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 805             }
 806             ast::MetaItemKind::NameValue(ref literal) => {
 807                 let name = self.name.as_str();
 808                 // 3 = ` = `
 809                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 810                 let value = rewrite_literal(context, literal, lit_shape)?;
 811                 format!("{} = {}", name, value)
 812             }
 813         })
 814     }
 815 }
 816
 817 impl Rewrite for ast::Attribute {
 818     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 819         let prefix = match self.style {
 820             ast::AttrStyle::Inner => "#!",
 821             ast::AttrStyle::Outer => "#",
 822         };
 823         let snippet = context.snippet(self.span);
 824         if self.is_sugared_doc {
 825             let doc_shape = Shape {
 826                 width: cmp::min(shape.width, context.config.comment_width())
 827                     .checked_sub(shape.indent.width())
 828                     .unwrap_or(0),
 829                 ..shape
 830             };
 831             rewrite_comment(snippet, false, doc_shape, context.config)
 832         } else {
 833             if contains_comment(snippet) {
 834                 return Some(snippet.into());
 835             }
 836             // 1 = `[`
 837             let shape = shape.offset_left(prefix.len() + 1)?;
 838             self.meta()?
 839                 .rewrite(context, shape)
 840                 .map(|rw| format!("{}[{}]", prefix, rw))
 841         }
 842     }
 843 }
 844
 845 /// Returns the first group of attributes that fills the given predicate.
 846 /// We consider two doc comments are in different group if they are separated by normal comments.
 847 fn take_while_with_pred<'a, P>(
 848     context: &RewriteContext,
 849     attrs: &'a [ast::Attribute],
 850     pred: P,
 851 ) -> &'a [ast::Attribute]
 852 where
 853     P: Fn(&ast::Attribute) -> bool,
 854 {
 855     let mut last_index = 0;
 856     let mut iter = attrs.iter().enumerate().peekable();
 857     while let Some((i, attr)) = iter.next() {
 858         if !pred(attr) {
 859             break;
 860         }
 861         if let Some(&(_, next_attr)) = iter.peek() {
 862             // Extract comments between two attributes.
 863             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 864             let snippet = context.snippet(span_between_attr);
 865             if count_newlines(&snippet) >= 2 || snippet.contains('/') {
 866                 break;
 867             }
 868         }
 869         last_index = i;
 870     }
 871     if last_index == 0 {
 872         &[]
 873     } else {
 874         &attrs[..last_index + 1]
 875     }
 876 }
 877
 878 fn rewrite_first_group_attrs(
 879     context: &RewriteContext,
 880     attrs: &[ast::Attribute],
 881     shape: Shape,
 882 ) -> Option<(usize, String)> {
 883     if attrs.is_empty() {
 884         return Some((0, String::new()));
 885     }
 886     // Rewrite doc comments
 887     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 888     if !sugared_docs.is_empty() {
 889         let snippet = sugared_docs
 890             .iter()
 891             .map(|a| context.snippet(a.span))
 892             .collect::<Vec<_>>()
 893             .join("\n");
 894         return Some((
 895             sugared_docs.len(),
 896             rewrite_comment(&snippet, false, shape, context.config)?,
 897         ));
 898     }
 899     // Rewrite `#[derive(..)]`s.
 900     if context.config.merge_derives() {
 901         let derives = take_while_with_pred(context, attrs, is_derive);
 902         if !derives.is_empty() {
 903             let mut derive_args = vec![];
 904             for derive in derives {
 905                 derive_args.append(&mut get_derive_args(context, derive)?);
 906             }
 907             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 908         }
 909     }
 910     // Rewrite the first attribute.
 911     Some((1, attrs[0].rewrite(context, shape)?))
 912 }
 913
 914 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 915     // Look at before and after comment and see if there are any empty lines.
 916     let comment_begin = comment.chars().position(|c| c == '/');
 917     let len = comment_begin.unwrap_or_else(|| comment.len());
 918     let mlb = count_newlines(&comment[..len]) > 1;
 919     let mla = if comment_begin.is_none() {
 920         mlb
 921     } else {
 922         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 923         let len = comment_end.unwrap();
 924         comment
 925             .chars()
 926             .rev()
 927             .take(len)
 928             .filter(|c| *c == '\n')
 929             .count() > 1
 930     };
 931     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 932 }
 933
 934 impl<'a> Rewrite for [ast::Attribute] {
 935     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 936         if self.is_empty() {
 937             return Some(String::new());
 938         }
 939         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 940         if self.len() == 1 || first_group_len == self.len() {
 941             Some(first_group_str)
 942         } else {
 943             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 944             let missing_span = mk_sp(
 945                 self[first_group_len - 1].span.hi(),
 946                 self[first_group_len].span.lo(),
 947             );
 948             // Preserve an empty line before/after doc comments.
 949             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 950                 let snippet = context.snippet(missing_span);
 951                 let (mla, mlb) = has_newlines_before_after_comment(&snippet);
 952                 let comment = ::comment::recover_missing_comment_in_span(
 953                     missing_span,
 954                     shape.with_max_width(context.config),
 955                     context,
 956                     0,
 957                 )?;
 958                 let comment = if comment.is_empty() {
 959                     format!("\n{}", mlb)
 960                 } else {
 961                     format!("{}{}\n{}", mla, comment, mlb)
 962                 };
 963                 Some(format!(
 964                     "{}{}{}{}",
 965                     first_group_str,
 966                     comment,
 967                     shape.indent.to_string(context.config),
 968                     rest_str
 969                 ))
 970             } else {
 971                 combine_strs_with_missing_comments(
 972                     context,
 973                     &first_group_str,
 974                     &rest_str,
 975                     missing_span,
 976                     shape,
 977                     false,
 978                 )
 979             }
 980         }
 981     }
 982 }
 983
 984 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
 985 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
 986     let mut result = String::with_capacity(128);
 987     result.push_str("#[derive(");
 988     // 11 = `#[derive()]`
 989     let initial_budget = shape.width.checked_sub(11)?;
 990     let mut budget = initial_budget;
 991     let num = derive_args.len();
 992     for (i, a) in derive_args.iter().enumerate() {
 993         // 2 = `, ` or `)]`
 994         let width = a.len() + 2;
 995         if width > budget {
 996             if i > 0 {
 997                 // Remove trailing whitespace.
 998                 result.pop();
 999             }
1000             result.push('\n');
1001             // 9 = `#[derive(`
1002             result.push_str(&(shape.indent + 9).to_string(context.config));
1003             budget = initial_budget;
1004         } else {
1005             budget = budget.checked_sub(width).unwrap_or(0);
1006         }
1007         result.push_str(a);
1008         if i != num - 1 {
1009             result.push_str(", ")
1010         }
1011     }
1012     result.push_str(")]");
1013     Some(result)
1014 }
1015
1016 fn is_derive(attr: &ast::Attribute) -> bool {
1017     match attr.meta() {
1018         Some(meta_item) => match meta_item.node {
1019             ast::MetaItemKind::List(..) => meta_item.name.as_str() == "derive",
1020             _ => false,
1021         },
1022         _ => false,
1023     }
1024 }
1025
1026 /// Returns the arguments of `#[derive(...)]`.
1027 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1028     attr.meta().and_then(|meta_item| match meta_item.node {
1029         ast::MetaItemKind::List(ref args) if meta_item.name.as_str() == "derive" => {
1030             // Every argument of `derive` should be `NestedMetaItemKind::Literal`.
1031             Some(
1032                 args.iter()
1033                     .map(|a| context.snippet(a.span))
1034                     .collect::<Vec<_>>(),
1035             )
1036         }
1037         _ => None,
1038     })
1039 }
1040
1041 // Rewrite `extern crate foo;` WITHOUT attributes.
1042 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1043     assert!(is_extern_crate(item));
1044     let new_str = context.snippet(item.span);
1045     Some(if contains_comment(&new_str) {
1046         new_str.into()
1047     } else {
1048         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1049         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1050     })
1051 }