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