src/visitor.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::cmp;
  12
  13 use syntax::{ast, visit};
  14 use syntax::attr::HasAttrs;
  15 use syntax::codemap::{self, BytePos, CodeMap, Pos, Span};
  16 use syntax::parse::ParseSess;
  17
  18 use codemap::{LineRangeUtils, SpanUtils};
  19 use comment::{combine_strs_with_missing_comments, contains_comment, CodeCharKind,
  20               CommentCodeSlices, FindUncommented};
  21 use comment::rewrite_comment;
  22 use config::{BraceStyle, Config};
  23 use expr::rewrite_literal;
  24 use items::{format_impl, format_trait, format_trait_alias, rewrite_associated_impl_type,
  25             rewrite_associated_type, rewrite_type_alias, FnSig, StaticParts, StructParts};
  26 use lists::{itemize_list, write_list, DefinitiveListTactic, ListFormatting, SeparatorPlace,
  27             SeparatorTactic};
  28 use macros::{rewrite_macro, rewrite_macro_def, MacroPosition};
  29 use regex::Regex;
  30 use rewrite::{Rewrite, RewriteContext};
  31 use shape::{Indent, Shape};
  32 use spanned::Spanned;
  33 use utils::{self, contains_skip, count_newlines, inner_attributes, mk_sp, ptr_vec_to_ref_vec};
  34
  35 fn is_use_item(item: &ast::Item) -> bool {
  36     match item.node {
  37         ast::ItemKind::Use(_) => true,
  38         _ => false,
  39     }
  40 }
  41
  42 fn is_extern_crate(item: &ast::Item) -> bool {
  43     match item.node {
  44         ast::ItemKind::ExternCrate(..) => true,
  45         _ => false,
  46     }
  47 }
  48
  49 /// Creates a string slice corresponding to the specified span.
  50 pub struct SnippetProvider<'a> {
  51     /// A pointer to the content of the file we are formatting.
  52     big_snippet: &'a str,
  53     /// A position of the start of `big_snippet`, used as an offset.
  54     start_pos: usize,
  55 }
  56
  57 impl<'a> SnippetProvider<'a> {
  58     pub fn span_to_snippet(&self, span: Span) -> Option<&str> {
  59         let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
  60         let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
  61         Some(&self.big_snippet[start_index..end_index])
  62     }
  63
  64     pub fn new(start_pos: BytePos, big_snippet: &'a str) -> Self {
  65         let start_pos = start_pos.to_usize();
  66         SnippetProvider {
  67             big_snippet,
  68             start_pos,
  69         }
  70     }
  71 }
  72
  73 pub struct FmtVisitor<'a> {
  74     pub parse_session: &'a ParseSess,
  75     pub codemap: &'a CodeMap,
  76     pub buffer: String,
  77     pub last_pos: BytePos,
  78     // FIXME: use an RAII util or closure for indenting
  79     pub block_indent: Indent,
  80     pub config: &'a Config,
  81     pub is_if_else_block: bool,
  82     pub snippet_provider: &'a SnippetProvider<'a>,
  83     pub line_number: usize,
  84     pub skipped_range: Vec<(usize, usize)>,
  85 }
  86
  87 impl<'b, 'a: 'b> FmtVisitor<'a> {
  88     pub fn shape(&self) -> Shape {
  89         Shape::indented(self.block_indent, self.config)
  90     }
  91
  92     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  93         debug!(
  94             "visit_stmt: {:?} {:?}",
  95             self.codemap.lookup_char_pos(stmt.span.lo()),
  96             self.codemap.lookup_char_pos(stmt.span.hi())
  97         );
  98
  99         match stmt.node {
 100             ast::StmtKind::Item(ref item) => {
 101                 self.visit_item(item);
 102             }
 103             ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
 104                 if contains_skip(get_attrs_from_stmt(stmt)) {
 105                     self.push_skipped_with_span(stmt.span());
 106                 } else {
 107                     let rewrite = stmt.rewrite(&self.get_context(), self.shape());
 108                     self.push_rewrite(stmt.span(), rewrite)
 109                 }
 110             }
 111             ast::StmtKind::Mac(ref mac) => {
 112                 let (ref mac, _macro_style, ref attrs) = **mac;
 113                 if self.visit_attrs(attrs, ast::AttrStyle::Outer) {
 114                     self.push_skipped_with_span(stmt.span());
 115                 } else {
 116                     self.visit_mac(mac, None, MacroPosition::Statement);
 117                 }
 118                 self.format_missing(stmt.span.hi());
 119             }
 120         }
 121     }
 122
 123     pub fn visit_block(
 124         &mut self,
 125         b: &ast::Block,
 126         inner_attrs: Option<&[ast::Attribute]>,
 127         has_braces: bool,
 128     ) {
 129         debug!(
 130             "visit_block: {:?} {:?}",
 131             self.codemap.lookup_char_pos(b.span.lo()),
 132             self.codemap.lookup_char_pos(b.span.hi())
 133         );
 134
 135         // Check if this block has braces.
 136         let brace_compensation = BytePos(if has_braces { 1 } else { 0 });
 137
 138         self.last_pos = self.last_pos + brace_compensation;
 139         self.block_indent = self.block_indent.block_indent(self.config);
 140         self.push_str("{");
 141
 142         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 143             if let Some(first_stmt) = b.stmts.first() {
 144                 let attr_lo = inner_attrs
 145                     .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
 146                     .or_else(|| {
 147                         // Attributes for an item in a statement position
 148                         // do not belong to the statement. (rust-lang/rust#34459)
 149                         if let ast::StmtKind::Item(ref item) = first_stmt.node {
 150                             item.attrs.first()
 151                         } else {
 152                             first_stmt.attrs().first()
 153                         }.and_then(|attr| {
 154                             // Some stmts can have embedded attributes.
 155                             // e.g. `match { #![attr] ... }`
 156                             let attr_lo = attr.span.lo();
 157                             if attr_lo < first_stmt.span.lo() {
 158                                 Some(attr_lo)
 159                             } else {
 160                                 None
 161                             }
 162                         })
 163                     });
 164
 165                 let snippet = self.snippet(mk_sp(
 166                     self.last_pos,
 167                     attr_lo.unwrap_or(first_stmt.span.lo()),
 168                 ));
 169                 let len = CommentCodeSlices::new(snippet)
 170                     .nth(0)
 171                     .and_then(|(kind, _, s)| {
 172                         if kind == CodeCharKind::Normal {
 173                             s.rfind('\n')
 174                         } else {
 175                             None
 176                         }
 177                     });
 178                 if let Some(len) = len {
 179                     self.last_pos = self.last_pos + BytePos::from_usize(len);
 180                 }
 181             }
 182         }
 183
 184         // Format inner attributes if available.
 185         let skip_rewrite = if let Some(attrs) = inner_attrs {
 186             self.visit_attrs(attrs, ast::AttrStyle::Inner)
 187         } else {
 188             false
 189         };
 190
 191         if skip_rewrite {
 192             self.push_rewrite(b.span, None);
 193             self.close_block(false);
 194             self.last_pos = source!(self, b.span).hi();
 195             return;
 196         }
 197
 198         self.walk_block_stmts(b);
 199
 200         if !b.stmts.is_empty() {
 201             if let Some(expr) = utils::stmt_expr(&b.stmts[b.stmts.len() - 1]) {
 202                 if utils::semicolon_for_expr(&self.get_context(), expr) {
 203                     self.push_str(";");
 204                 }
 205             }
 206         }
 207
 208         let mut remove_len = BytePos(0);
 209         if self.config.remove_blank_lines_at_start_or_end_of_block() {
 210             if let Some(stmt) = b.stmts.last() {
 211                 let snippet = self.snippet(mk_sp(
 212                     stmt.span.hi(),
 213                     source!(self, b.span).hi() - brace_compensation,
 214                 ));
 215                 let len = CommentCodeSlices::new(snippet)
 216                     .last()
 217                     .and_then(|(kind, _, s)| {
 218                         if kind == CodeCharKind::Normal && s.trim().is_empty() {
 219                             Some(s.len())
 220                         } else {
 221                             None
 222                         }
 223                     });
 224                 if let Some(len) = len {
 225                     remove_len = BytePos::from_usize(len);
 226                 }
 227             }
 228         }
 229
 230         let unindent_comment = (self.is_if_else_block && !b.stmts.is_empty()) && {
 231             let end_pos = source!(self, b.span).hi() - brace_compensation - remove_len;
 232             let snippet = self.snippet(mk_sp(self.last_pos, end_pos));
 233             snippet.contains("//") || snippet.contains("/*")
 234         };
 235         // FIXME: we should compress any newlines here to just one
 236         if unindent_comment {
 237             self.block_indent = self.block_indent.block_unindent(self.config);
 238         }
 239         self.format_missing_with_indent(
 240             source!(self, b.span).hi() - brace_compensation - remove_len,
 241         );
 242         if unindent_comment {
 243             self.block_indent = self.block_indent.block_indent(self.config);
 244         }
 245         self.close_block(unindent_comment);
 246         self.last_pos = source!(self, b.span).hi();
 247     }
 248
 249     // FIXME: this is a terrible hack to indent the comments between the last
 250     // item in the block and the closing brace to the block's level.
 251     // The closing brace itself, however, should be indented at a shallower
 252     // level.
 253     fn close_block(&mut self, unindent_comment: bool) {
 254         let total_len = self.buffer.len();
 255         let chars_too_many = if unindent_comment {
 256             0
 257         } else if self.config.hard_tabs() {
 258             1
 259         } else {
 260             self.config.tab_spaces()
 261         };
 262         self.buffer.truncate(total_len - chars_too_many);
 263         self.push_str("}");
 264         self.block_indent = self.block_indent.block_unindent(self.config);
 265     }
 266
 267     // Note that this only gets called for function definitions. Required methods
 268     // on traits do not get handled here.
 269     fn visit_fn(
 270         &mut self,
 271         fk: visit::FnKind,
 272         generics: &ast::Generics,
 273         fd: &ast::FnDecl,
 274         s: Span,
 275         defaultness: ast::Defaultness,
 276         inner_attrs: Option<&[ast::Attribute]>,
 277     ) {
 278         let indent = self.block_indent;
 279         let block;
 280         let rewrite = match fk {
 281             visit::FnKind::ItemFn(ident, _, _, _, _, b) | visit::FnKind::Method(ident, _, _, b) => {
 282                 block = b;
 283                 self.rewrite_fn(
 284                     indent,
 285                     ident,
 286                     &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
 287                     mk_sp(s.lo(), b.span.lo()),
 288                     b,
 289                 )
 290             }
 291             visit::FnKind::Closure(_) => unreachable!(),
 292         };
 293
 294         if let Some(fn_str) = rewrite {
 295             self.format_missing_with_indent(source!(self, s).lo());
 296             self.push_str(&fn_str);
 297             if let Some(c) = fn_str.chars().last() {
 298                 if c == '}' {
 299                     self.last_pos = source!(self, block.span).hi();
 300                     return;
 301                 }
 302             }
 303         } else {
 304             self.format_missing(source!(self, block.span).lo());
 305         }
 306
 307         self.last_pos = source!(self, block.span).lo();
 308         self.visit_block(block, inner_attrs, true)
 309     }
 310
 311     pub fn visit_item(&mut self, item: &ast::Item) {
 312         skip_out_of_file_lines_range_visitor!(self, item.span);
 313
 314         // This is where we bail out if there is a skip attribute. This is only
 315         // complex in the module case. It is complex because the module could be
 316         // in a separate file and there might be attributes in both files, but
 317         // the AST lumps them all together.
 318         let filtered_attrs;
 319         let mut attrs = &item.attrs;
 320         match item.node {
 321             ast::ItemKind::Mod(ref m) => {
 322                 let outer_file = self.codemap.lookup_char_pos(item.span.lo()).file;
 323                 let inner_file = self.codemap.lookup_char_pos(m.inner.lo()).file;
 324                 if outer_file.name == inner_file.name {
 325                     // Module is inline, in this case we treat modules like any
 326                     // other item.
 327                     if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 328                         self.push_skipped_with_span(item.span());
 329                         return;
 330                     }
 331                 } else if contains_skip(&item.attrs) {
 332                     // Module is not inline, but should be skipped.
 333                     return;
 334                 } else {
 335                     // Module is not inline and should not be skipped. We want
 336                     // to process only the attributes in the current file.
 337                     filtered_attrs = item.attrs
 338                         .iter()
 339                         .filter_map(|a| {
 340                             let attr_file = self.codemap.lookup_char_pos(a.span.lo()).file;
 341                             if attr_file.name == outer_file.name {
 342                                 Some(a.clone())
 343                             } else {
 344                                 None
 345                             }
 346                         })
 347                         .collect::<Vec<_>>();
 348                     // Assert because if we should skip it should be caught by
 349                     // the above case.
 350                     assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
 351                     attrs = &filtered_attrs;
 352                 }
 353             }
 354             _ => {
 355                 if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
 356                     self.push_skipped_with_span(item.span());
 357                     return;
 358                 }
 359             }
 360         }
 361
 362         match item.node {
 363             ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
 364             ast::ItemKind::Impl(..) => {
 365                 let snippet = self.snippet(item.span);
 366                 let where_span_end = snippet
 367                     .find_uncommented("{")
 368                     .map(|x| (BytePos(x as u32)) + source!(self, item.span).lo());
 369                 let rw = format_impl(&self.get_context(), item, self.block_indent, where_span_end);
 370                 self.push_rewrite(item.span, rw);
 371             }
 372             ast::ItemKind::Trait(..) => {
 373                 let rw = format_trait(&self.get_context(), item, self.block_indent);
 374                 self.push_rewrite(item.span, rw);
 375             }
 376             ast::ItemKind::TraitAlias(ref generics, ref ty_param_bounds) => {
 377                 let shape = Shape::indented(self.block_indent, self.config);
 378                 let rw = format_trait_alias(
 379                     &self.get_context(),
 380                     item.ident,
 381                     generics,
 382                     ty_param_bounds,
 383                     shape,
 384                 );
 385                 self.push_rewrite(item.span, rw);
 386             }
 387             ast::ItemKind::ExternCrate(_) => {
 388                 let rw = rewrite_extern_crate(&self.get_context(), item);
 389                 self.push_rewrite(item.span, rw);
 390             }
 391             ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
 392                 self.visit_struct(&StructParts::from_item(item));
 393             }
 394             ast::ItemKind::Enum(ref def, ref generics) => {
 395                 self.format_missing_with_indent(source!(self, item.span).lo());
 396                 self.visit_enum(item.ident, &item.vis, def, generics, item.span);
 397                 self.last_pos = source!(self, item.span).hi();
 398             }
 399             ast::ItemKind::Mod(ref module) => {
 400                 self.format_missing_with_indent(source!(self, item.span).lo());
 401                 self.format_mod(module, &item.vis, item.span, item.ident, attrs);
 402             }
 403             ast::ItemKind::Mac(ref mac) => {
 404                 self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
 405             }
 406             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 407                 self.format_missing_with_indent(source!(self, item.span).lo());
 408                 self.format_foreign_mod(foreign_mod, item.span);
 409             }
 410             ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
 411                 self.visit_static(&StaticParts::from_item(item));
 412             }
 413             ast::ItemKind::AutoImpl(..) => {
 414                 // FIXME(#78): format impl definitions.
 415             }
 416             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 417                 self.visit_fn(
 418                     visit::FnKind::ItemFn(item.ident, unsafety, constness, abi, &item.vis, body),
 419                     generics,
 420                     decl,
 421                     item.span,
 422                     ast::Defaultness::Final,
 423                     Some(&item.attrs),
 424                 )
 425             }
 426             ast::ItemKind::Ty(ref ty, ref generics) => {
 427                 let rewrite = rewrite_type_alias(
 428                     &self.get_context(),
 429                     self.block_indent,
 430                     item.ident,
 431                     ty,
 432                     generics,
 433                     &item.vis,
 434                     item.span,
 435                 );
 436                 self.push_rewrite(item.span, rewrite);
 437             }
 438             ast::ItemKind::GlobalAsm(..) => {
 439                 let snippet = Some(self.snippet(item.span).to_owned());
 440                 self.push_rewrite(item.span, snippet);
 441             }
 442             ast::ItemKind::MacroDef(ref def) => {
 443                 let rewrite = rewrite_macro_def(
 444                     &self.get_context(),
 445                     self.block_indent,
 446                     def,
 447                     item.ident,
 448                     &item.vis,
 449                     item.span,
 450                 );
 451                 self.push_rewrite(item.span, rewrite);
 452             }
 453         }
 454     }
 455
 456     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 457         skip_out_of_file_lines_range_visitor!(self, ti.span);
 458
 459         if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
 460             self.push_skipped_with_span(ti.span());
 461             return;
 462         }
 463
 464         match ti.node {
 465             ast::TraitItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
 466             ast::TraitItemKind::Method(ref sig, None) => {
 467                 let indent = self.block_indent;
 468                 let rewrite =
 469                     self.rewrite_required_fn(indent, ti.ident, sig, &ti.generics, ti.span);
 470                 self.push_rewrite(ti.span, rewrite);
 471             }
 472             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 473                 self.visit_fn(
 474                     visit::FnKind::Method(ti.ident, sig, None, body),
 475                     &ti.generics,
 476                     &sig.decl,
 477                     ti.span,
 478                     ast::Defaultness::Final,
 479                     Some(&ti.attrs),
 480                 );
 481             }
 482             ast::TraitItemKind::Type(ref type_param_bounds, ref type_default) => {
 483                 let rewrite = rewrite_associated_type(
 484                     ti.ident,
 485                     type_default.as_ref(),
 486                     Some(type_param_bounds),
 487                     &self.get_context(),
 488                     self.block_indent,
 489                 );
 490                 self.push_rewrite(ti.span, rewrite);
 491             }
 492             ast::TraitItemKind::Macro(ref mac) => {
 493                 self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
 494             }
 495         }
 496     }
 497
 498     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 499         skip_out_of_file_lines_range_visitor!(self, ii.span);
 500
 501         if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
 502             self.push_skipped_with_span(ii.span());
 503             return;
 504         }
 505
 506         match ii.node {
 507             ast::ImplItemKind::Method(ref sig, ref body) => {
 508                 self.visit_fn(
 509                     visit::FnKind::Method(ii.ident, sig, Some(&ii.vis), body),
 510                     &ii.generics,
 511                     &sig.decl,
 512                     ii.span,
 513                     ii.defaultness,
 514                     Some(&ii.attrs),
 515                 );
 516             }
 517             ast::ImplItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
 518             ast::ImplItemKind::Type(ref ty) => {
 519                 let rewrite = rewrite_associated_impl_type(
 520                     ii.ident,
 521                     ii.defaultness,
 522                     Some(ty),
 523                     None,
 524                     &self.get_context(),
 525                     self.block_indent,
 526                 );
 527                 self.push_rewrite(ii.span, rewrite);
 528             }
 529             ast::ImplItemKind::Macro(ref mac) => {
 530                 self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
 531             }
 532         }
 533     }
 534
 535     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>, pos: MacroPosition) {
 536         skip_out_of_file_lines_range_visitor!(self, mac.span);
 537
 538         // 1 = ;
 539         let shape = self.shape().sub_width(1).unwrap();
 540         let rewrite = rewrite_macro(mac, ident, &self.get_context(), shape, pos);
 541         self.push_rewrite(mac.span, rewrite);
 542     }
 543
 544     pub fn push_str(&mut self, s: &str) {
 545         self.line_number += count_newlines(s);
 546         self.buffer.push_str(s);
 547     }
 548
 549     fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
 550         if let Some(ref s) = rewrite {
 551             self.push_str(s);
 552         } else {
 553             let snippet = self.snippet(span);
 554             self.push_str(snippet);
 555         }
 556         self.last_pos = source!(self, span).hi();
 557     }
 558
 559     pub fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 560         self.format_missing_with_indent(source!(self, span).lo());
 561         self.push_rewrite_inner(span, rewrite);
 562     }
 563
 564     pub fn push_skipped_with_span(&mut self, span: Span) {
 565         self.format_missing_with_indent(source!(self, span).lo());
 566         let lo = self.line_number + 1;
 567         self.push_rewrite_inner(span, None);
 568         let hi = self.line_number + 1;
 569         self.skipped_range.push((lo, hi));
 570     }
 571
 572     pub fn from_context(ctx: &'a RewriteContext) -> FmtVisitor<'a> {
 573         FmtVisitor::from_codemap(ctx.parse_session, ctx.config, ctx.snippet_provider)
 574     }
 575
 576     pub fn from_codemap(
 577         parse_session: &'a ParseSess,
 578         config: &'a Config,
 579         snippet_provider: &'a SnippetProvider,
 580     ) -> FmtVisitor<'a> {
 581         FmtVisitor {
 582             parse_session: parse_session,
 583             codemap: parse_session.codemap(),
 584             buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
 585             last_pos: BytePos(0),
 586             block_indent: Indent::empty(),
 587             config: config,
 588             is_if_else_block: false,
 589             snippet_provider: snippet_provider,
 590             line_number: 0,
 591             skipped_range: vec![],
 592         }
 593     }
 594
 595     pub fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
 596         self.snippet_provider.span_to_snippet(span)
 597     }
 598
 599     pub fn snippet(&'b self, span: Span) -> &'a str {
 600         self.opt_snippet(span).unwrap()
 601     }
 602
 603     // Returns true if we should skip the following item.
 604     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
 605         if contains_skip(attrs) {
 606             return true;
 607         }
 608
 609         let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
 610         if attrs.is_empty() {
 611             return false;
 612         }
 613
 614         let rewrite = attrs.rewrite(&self.get_context(), self.shape());
 615         let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
 616         self.push_rewrite(span, rewrite);
 617
 618         false
 619     }
 620
 621     fn reorder_items<F>(&mut self, items_left: &[&ast::Item], is_item: &F, in_group: bool) -> usize
 622     where
 623         F: Fn(&ast::Item) -> bool,
 624     {
 625         let mut last = self.codemap.lookup_line_range(items_left[0].span());
 626         let item_length = items_left
 627             .iter()
 628             .take_while(|ppi| {
 629                 is_item(&***ppi) && (!in_group || {
 630                     let current = self.codemap.lookup_line_range(ppi.span());
 631                     let in_same_group = current.lo < last.hi + 2;
 632                     last = current;
 633                     in_same_group
 634                 })
 635             })
 636             .count();
 637         let items = &items_left[..item_length];
 638
 639         let at_least_one_in_file_lines = items
 640             .iter()
 641             .any(|item| !out_of_file_lines_range!(self, item.span));
 642
 643         if at_least_one_in_file_lines {
 644             self.format_imports(items);
 645         } else {
 646             for item in items {
 647                 self.push_rewrite(item.span, None);
 648             }
 649         }
 650
 651         item_length
 652     }
 653
 654     fn walk_items(&mut self, mut items_left: &[&ast::Item]) {
 655         while !items_left.is_empty() {
 656             // If the next item is a `use` declaration, then extract it and any subsequent `use`s
 657             // to be potentially reordered within `format_imports`. Otherwise, just format the
 658             // next item for output.
 659             if self.config.reorder_imports() && is_use_item(&*items_left[0]) {
 660                 let used_items_len = self.reorder_items(
 661                     items_left,
 662                     &is_use_item,
 663                     self.config.reorder_imports_in_group(),
 664                 );
 665                 let (_, rest) = items_left.split_at(used_items_len);
 666                 items_left = rest;
 667             } else if self.config.reorder_extern_crates() && is_extern_crate(&*items_left[0]) {
 668                 let used_items_len = self.reorder_items(
 669                     items_left,
 670                     &is_extern_crate,
 671                     self.config.reorder_extern_crates_in_group(),
 672                 );
 673                 let (_, rest) = items_left.split_at(used_items_len);
 674                 items_left = rest;
 675             } else {
 676                 // `unwrap()` is safe here because we know `items_left`
 677                 // has elements from the loop condition
 678                 let (item, rest) = items_left.split_first().unwrap();
 679                 self.visit_item(item);
 680                 items_left = rest;
 681             }
 682         }
 683     }
 684
 685     fn walk_mod_items(&mut self, m: &ast::Mod) {
 686         self.walk_items(&ptr_vec_to_ref_vec(&m.items));
 687     }
 688
 689     fn walk_stmts(&mut self, stmts: &[ast::Stmt]) {
 690         fn to_stmt_item(stmt: &ast::Stmt) -> Option<&ast::Item> {
 691             match stmt.node {
 692                 ast::StmtKind::Item(ref item) => Some(&**item),
 693                 _ => None,
 694             }
 695         }
 696
 697         if stmts.is_empty() {
 698             return;
 699         }
 700
 701         // Extract leading `use ...;`.
 702         let items: Vec<_> = stmts
 703             .iter()
 704             .take_while(|stmt| to_stmt_item(stmt).map_or(false, is_use_item))
 705             .filter_map(|stmt| to_stmt_item(stmt))
 706             .collect();
 707
 708         if items.is_empty() {
 709             self.visit_stmt(&stmts[0]);
 710             self.walk_stmts(&stmts[1..]);
 711         } else {
 712             self.walk_items(&items);
 713             self.walk_stmts(&stmts[items.len()..]);
 714         }
 715     }
 716
 717     fn walk_block_stmts(&mut self, b: &ast::Block) {
 718         self.walk_stmts(&b.stmts)
 719     }
 720
 721     fn format_mod(
 722         &mut self,
 723         m: &ast::Mod,
 724         vis: &ast::Visibility,
 725         s: Span,
 726         ident: ast::Ident,
 727         attrs: &[ast::Attribute],
 728     ) {
 729         // Decide whether this is an inline mod or an external mod.
 730         let local_file_name = self.codemap.span_to_filename(s);
 731         let inner_span = source!(self, m.inner);
 732         let is_internal = !(inner_span.lo().0 == 0 && inner_span.hi().0 == 0)
 733             && local_file_name == self.codemap.span_to_filename(inner_span);
 734
 735         self.push_str(&*utils::format_visibility(vis));
 736         self.push_str("mod ");
 737         self.push_str(&ident.to_string());
 738
 739         if is_internal {
 740             match self.config.brace_style() {
 741                 BraceStyle::AlwaysNextLine => {
 742                     let sep_str = format!("\n{}{{", self.block_indent.to_string(self.config));
 743                     self.push_str(&sep_str);
 744                 }
 745                 _ => self.push_str(" {"),
 746             }
 747             // Hackery to account for the closing }.
 748             let mod_lo = self.codemap.span_after(source!(self, s), "{");
 749             let body_snippet =
 750                 self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
 751             let body_snippet = body_snippet.trim();
 752             if body_snippet.is_empty() {
 753                 self.push_str("}");
 754             } else {
 755                 self.last_pos = mod_lo;
 756                 self.block_indent = self.block_indent.block_indent(self.config);
 757                 self.visit_attrs(attrs, ast::AttrStyle::Inner);
 758                 self.walk_mod_items(m);
 759                 self.format_missing_with_indent(source!(self, m.inner).hi() - BytePos(1));
 760                 self.close_block(false);
 761             }
 762             self.last_pos = source!(self, m.inner).hi();
 763         } else {
 764             self.push_str(";");
 765             self.last_pos = source!(self, s).hi();
 766         }
 767     }
 768
 769     pub fn format_separate_mod(&mut self, m: &ast::Mod, filemap: &codemap::FileMap) {
 770         self.block_indent = Indent::empty();
 771         self.walk_mod_items(m);
 772         self.format_missing_with_indent(filemap.end_pos);
 773     }
 774
 775     pub fn skip_empty_lines(&mut self, end_pos: BytePos) {
 776         while let Some(pos) = self.codemap
 777             .opt_span_after(mk_sp(self.last_pos, end_pos), "\n")
 778         {
 779             if let Some(snippet) = self.opt_snippet(mk_sp(self.last_pos, pos)) {
 780                 if snippet.trim().is_empty() {
 781                     self.last_pos = pos;
 782                 } else {
 783                     return;
 784                 }
 785             }
 786         }
 787     }
 788
 789     pub fn get_context(&self) -> RewriteContext {
 790         RewriteContext {
 791             parse_session: self.parse_session,
 792             codemap: self.codemap,
 793             config: self.config,
 794             inside_macro: false,
 795             use_block: false,
 796             is_if_else_block: false,
 797             force_one_line_chain: false,
 798             snippet_provider: self.snippet_provider,
 799         }
 800     }
 801 }
 802
 803 impl Rewrite for ast::NestedMetaItem {
 804     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 805         match self.node {
 806             ast::NestedMetaItemKind::MetaItem(ref meta_item) => meta_item.rewrite(context, shape),
 807             ast::NestedMetaItemKind::Literal(ref l) => rewrite_literal(context, l, shape),
 808         }
 809     }
 810 }
 811
 812 impl Rewrite for ast::MetaItem {
 813     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 814         Some(match self.node {
 815             ast::MetaItemKind::Word => String::from(&*self.name.as_str()),
 816             ast::MetaItemKind::List(ref list) => {
 817                 let name = self.name.as_str();
 818                 // 1 = `(`, 2 = `]` and `)`
 819                 let item_shape = shape
 820                     .visual_indent(0)
 821                     .shrink_left(name.len() + 1)
 822                     .and_then(|s| s.sub_width(2))?;
 823                 let items = itemize_list(
 824                     context.codemap,
 825                     list.iter(),
 826                     ")",
 827                     ",",
 828                     |nested_meta_item| nested_meta_item.span.lo(),
 829                     |nested_meta_item| nested_meta_item.span.hi(),
 830                     |nested_meta_item| nested_meta_item.rewrite(context, item_shape),
 831                     self.span.lo(),
 832                     self.span.hi(),
 833                     false,
 834                 );
 835                 let item_vec = items.collect::<Vec<_>>();
 836                 let fmt = ListFormatting {
 837                     tactic: DefinitiveListTactic::Mixed,
 838                     separator: ",",
 839                     trailing_separator: SeparatorTactic::Never,
 840                     separator_place: SeparatorPlace::Back,
 841                     shape: item_shape,
 842                     ends_with_newline: false,
 843                     preserve_newline: false,
 844                     config: context.config,
 845                 };
 846                 format!("{}({})", name, write_list(&item_vec, &fmt)?)
 847             }
 848             ast::MetaItemKind::NameValue(ref literal) => {
 849                 let name = self.name.as_str();
 850                 // 3 = ` = `
 851                 let lit_shape = shape.shrink_left(name.len() + 3)?;
 852                 let value = rewrite_literal(context, literal, lit_shape)?;
 853                 format!("{} = {}", name, value)
 854             }
 855         })
 856     }
 857 }
 858
 859 impl Rewrite for ast::Attribute {
 860     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 861         let prefix = match self.style {
 862             ast::AttrStyle::Inner => "#!",
 863             ast::AttrStyle::Outer => "#",
 864         };
 865         let snippet = context.snippet(self.span);
 866         if self.is_sugared_doc {
 867             let doc_shape = Shape {
 868                 width: cmp::min(shape.width, context.config.comment_width())
 869                     .checked_sub(shape.indent.width())
 870                     .unwrap_or(0),
 871                 ..shape
 872             };
 873             rewrite_comment(snippet, false, doc_shape, context.config)
 874         } else {
 875             if contains_comment(snippet) {
 876                 return Some(snippet.to_owned());
 877             }
 878             // 1 = `[`
 879             let shape = shape.offset_left(prefix.len() + 1)?;
 880             self.meta()?
 881                 .rewrite(context, shape)
 882                 .map(|rw| format!("{}[{}]", prefix, rw))
 883         }
 884     }
 885 }
 886
 887 /// Returns the first group of attributes that fills the given predicate.
 888 /// We consider two doc comments are in different group if they are separated by normal comments.
 889 fn take_while_with_pred<'a, P>(
 890     context: &RewriteContext,
 891     attrs: &'a [ast::Attribute],
 892     pred: P,
 893 ) -> &'a [ast::Attribute]
 894 where
 895     P: Fn(&ast::Attribute) -> bool,
 896 {
 897     let mut last_index = 0;
 898     let mut iter = attrs.iter().enumerate().peekable();
 899     while let Some((i, attr)) = iter.next() {
 900         if !pred(attr) {
 901             break;
 902         }
 903         if let Some(&(_, next_attr)) = iter.peek() {
 904             // Extract comments between two attributes.
 905             let span_between_attr = mk_sp(attr.span.hi(), next_attr.span.lo());
 906             let snippet = context.snippet(span_between_attr);
 907             if count_newlines(snippet) >= 2 || snippet.contains('/') {
 908                 break;
 909             }
 910         }
 911         last_index = i;
 912     }
 913     if last_index == 0 {
 914         &[]
 915     } else {
 916         &attrs[..last_index + 1]
 917     }
 918 }
 919
 920 fn rewrite_first_group_attrs(
 921     context: &RewriteContext,
 922     attrs: &[ast::Attribute],
 923     shape: Shape,
 924 ) -> Option<(usize, String)> {
 925     if attrs.is_empty() {
 926         return Some((0, String::new()));
 927     }
 928     // Rewrite doc comments
 929     let sugared_docs = take_while_with_pred(context, attrs, |a| a.is_sugared_doc);
 930     if !sugared_docs.is_empty() {
 931         let snippet = sugared_docs
 932             .iter()
 933             .map(|a| context.snippet(a.span))
 934             .collect::<Vec<_>>()
 935             .join("\n");
 936         return Some((
 937             sugared_docs.len(),
 938             rewrite_comment(&snippet, false, shape, context.config)?,
 939         ));
 940     }
 941     // Rewrite `#[derive(..)]`s.
 942     if context.config.merge_derives() {
 943         let derives = take_while_with_pred(context, attrs, is_derive);
 944         if !derives.is_empty() {
 945             let mut derive_args = vec![];
 946             for derive in derives {
 947                 derive_args.append(&mut get_derive_args(context, derive)?);
 948             }
 949             return Some((derives.len(), format_derive(context, &derive_args, shape)?));
 950         }
 951     }
 952     // Rewrite the first attribute.
 953     Some((1, attrs[0].rewrite(context, shape)?))
 954 }
 955
 956 fn has_newlines_before_after_comment(comment: &str) -> (&str, &str) {
 957     // Look at before and after comment and see if there are any empty lines.
 958     let comment_begin = comment.chars().position(|c| c == '/');
 959     let len = comment_begin.unwrap_or_else(|| comment.len());
 960     let mlb = count_newlines(&comment[..len]) > 1;
 961     let mla = if comment_begin.is_none() {
 962         mlb
 963     } else {
 964         let comment_end = comment.chars().rev().position(|c| !c.is_whitespace());
 965         let len = comment_end.unwrap();
 966         comment
 967             .chars()
 968             .rev()
 969             .take(len)
 970             .filter(|c| *c == '\n')
 971             .count() > 1
 972     };
 973     (if mlb { "\n" } else { "" }, if mla { "\n" } else { "" })
 974 }
 975
 976 impl<'a> Rewrite for [ast::Attribute] {
 977     fn rewrite(&self, context: &RewriteContext, shape: Shape) -> Option<String> {
 978         if self.is_empty() {
 979             return Some(String::new());
 980         }
 981         let (first_group_len, first_group_str) = rewrite_first_group_attrs(context, self, shape)?;
 982         if self.len() == 1 || first_group_len == self.len() {
 983             Some(first_group_str)
 984         } else {
 985             let rest_str = self[first_group_len..].rewrite(context, shape)?;
 986             let missing_span = mk_sp(
 987                 self[first_group_len - 1].span.hi(),
 988                 self[first_group_len].span.lo(),
 989             );
 990             // Preserve an empty line before/after doc comments.
 991             if self[0].is_sugared_doc || self[first_group_len].is_sugared_doc {
 992                 let snippet = context.snippet(missing_span);
 993                 let (mla, mlb) = has_newlines_before_after_comment(snippet);
 994                 let comment = ::comment::recover_missing_comment_in_span(
 995                     missing_span,
 996                     shape.with_max_width(context.config),
 997                     context,
 998                     0,
 999                 )?;
1000                 let comment = if comment.is_empty() {
1001                     format!("\n{}", mlb)
1002                 } else {
1003                     format!("{}{}\n{}", mla, comment, mlb)
1004                 };
1005                 Some(format!(
1006                     "{}{}{}{}",
1007                     first_group_str,
1008                     comment,
1009                     shape.indent.to_string(context.config),
1010                     rest_str
1011                 ))
1012             } else {
1013                 combine_strs_with_missing_comments(
1014                     context,
1015                     &first_group_str,
1016                     &rest_str,
1017                     missing_span,
1018                     shape,
1019                     false,
1020                 )
1021             }
1022         }
1023     }
1024 }
1025
1026 // Format `#[derive(..)]`, using visual indent & mixed style when we need to go multiline.
1027 fn format_derive(context: &RewriteContext, derive_args: &[&str], shape: Shape) -> Option<String> {
1028     let mut result = String::with_capacity(128);
1029     result.push_str("#[derive(");
1030     // 11 = `#[derive()]`
1031     let initial_budget = shape.width.checked_sub(11)?;
1032     let mut budget = initial_budget;
1033     let num = derive_args.len();
1034     for (i, a) in derive_args.iter().enumerate() {
1035         // 2 = `, ` or `)]`
1036         let width = a.len() + 2;
1037         if width > budget {
1038             if i > 0 {
1039                 // Remove trailing whitespace.
1040                 result.pop();
1041             }
1042             result.push('\n');
1043             // 9 = `#[derive(`
1044             result.push_str(&(shape.indent + 9).to_string(context.config));
1045             budget = initial_budget;
1046         } else {
1047             budget = budget.checked_sub(width).unwrap_or(0);
1048         }
1049         result.push_str(a);
1050         if i != num - 1 {
1051             result.push_str(", ")
1052         }
1053     }
1054     result.push_str(")]");
1055     Some(result)
1056 }
1057
1058 fn is_derive(attr: &ast::Attribute) -> bool {
1059     attr.check_name("derive")
1060 }
1061
1062 /// Returns the arguments of `#[derive(...)]`.
1063 fn get_derive_args<'a>(context: &'a RewriteContext, attr: &ast::Attribute) -> Option<Vec<&'a str>> {
1064     attr.meta_item_list().map(|meta_item_list| {
1065         meta_item_list
1066             .iter()
1067             .map(|nested_meta_item| context.snippet(nested_meta_item.span))
1068             .collect()
1069     })
1070 }
1071
1072 // Rewrite `extern crate foo;` WITHOUT attributes.
1073 pub fn rewrite_extern_crate(context: &RewriteContext, item: &ast::Item) -> Option<String> {
1074     assert!(is_extern_crate(item));
1075     let new_str = context.snippet(item.span);
1076     Some(if contains_comment(new_str) {
1077         new_str.to_owned()
1078     } else {
1079         let no_whitespace = &new_str.split_whitespace().collect::<Vec<&str>>().join(" ");
1080         String::from(&*Regex::new(r"\s;").unwrap().replace(no_whitespace, ";"))
1081     })
1082 }
1083
1084 fn get_attrs_from_stmt(stmt: &ast::Stmt) -> &[ast::Attribute] {
1085     match stmt.node {
1086         ast::StmtKind::Local(ref local) => &local.attrs,
1087         ast::StmtKind::Item(ref item) => &item.attrs,
1088         ast::StmtKind::Expr(ref expr) | ast::StmtKind::Semi(ref expr) => &expr.attrs,
1089         ast::StmtKind::Mac(ref mac) => &mac.2,
1090     }
1091 }