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 syntax::{ast, visit};
  12 use syntax::codemap::{self, CodeMap, Span, BytePos};
  13 use syntax::parse::ParseSess;
  14
  15 use strings::string_buffer::StringBuffer;
  16
  17 use Indent;
  18 use utils::{self, CodeMapSpanUtils};
  19 use config::Config;
  20 use rewrite::{Rewrite, RewriteContext};
  21 use comment::rewrite_comment;
  22 use macros::rewrite_macro;
  23 use items::{rewrite_static, rewrite_associated_type, rewrite_type_alias, format_impl, format_trait};
  24
  25 pub struct FmtVisitor<'a> {
  26     pub parse_session: &'a ParseSess,
  27     pub codemap: &'a CodeMap,
  28     pub buffer: StringBuffer,
  29     pub last_pos: BytePos,
  30     // FIXME: use an RAII util or closure for indenting
  31     pub block_indent: Indent,
  32     pub config: &'a Config,
  33 }
  34
  35 impl<'a> FmtVisitor<'a> {
  36     fn visit_stmt(&mut self, stmt: &ast::Stmt) {
  37         match stmt.node {
  38             ast::StmtKind::Decl(ref decl, _) => {
  39                 if let ast::DeclKind::Item(ref item) = decl.node {
  40                     self.visit_item(item);
  41                 } else {
  42                     let rewrite = stmt.rewrite(&self.get_context(),
  43                                                self.config.max_width - self.block_indent.width(),
  44                                                self.block_indent);
  45
  46                     self.push_rewrite(stmt.span, rewrite);
  47                 }
  48             }
  49             ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
  50                 let rewrite = stmt.rewrite(&self.get_context(),
  51                                            self.config.max_width - self.block_indent.width(),
  52                                            self.block_indent);
  53
  54                 self.push_rewrite(stmt.span, rewrite);
  55             }
  56             ast::StmtKind::Mac(ref mac, _macro_style, _) => {
  57                 self.format_missing_with_indent(stmt.span.lo);
  58                 self.visit_mac(mac, None);
  59             }
  60         }
  61     }
  62
  63     pub fn visit_block(&mut self, b: &ast::Block) {
  64         debug!("visit_block: {:?} {:?}",
  65                self.codemap.lookup_char_pos(b.span.lo),
  66                self.codemap.lookup_char_pos(b.span.hi));
  67
  68         // Check if this block has braces.
  69         let snippet = self.snippet(b.span);
  70         let has_braces = snippet.starts_with("{") || snippet.starts_with("unsafe");
  71         let brace_compensation = if has_braces {
  72             BytePos(1)
  73         } else {
  74             BytePos(0)
  75         };
  76
  77         self.last_pos = self.last_pos + brace_compensation;
  78         self.block_indent = self.block_indent.block_indent(self.config);
  79         self.buffer.push_str("{");
  80
  81         for stmt in &b.stmts {
  82             self.visit_stmt(&stmt)
  83         }
  84
  85         if let Some(ref e) = b.expr {
  86             self.format_missing_with_indent(e.span.lo);
  87             let rewrite = e.rewrite(&self.get_context(),
  88                                     self.config.max_width - self.block_indent.width(),
  89                                     self.block_indent)
  90                            .unwrap_or_else(|| self.snippet(e.span));
  91
  92             self.buffer.push_str(&rewrite);
  93             self.last_pos = e.span.hi;
  94
  95             if utils::semicolon_for_expr(e) {
  96                 self.buffer.push_str(";");
  97             }
  98         }
  99
 100         // FIXME: we should compress any newlines here to just one
 101         self.format_missing_with_indent(b.span.hi - brace_compensation);
 102         self.close_block();
 103         self.last_pos = b.span.hi;
 104     }
 105
 106     // FIXME: this is a terrible hack to indent the comments between the last
 107     // item in the block and the closing brace to the block's level.
 108     // The closing brace itself, however, should be indented at a shallower
 109     // level.
 110     fn close_block(&mut self) {
 111         let total_len = self.buffer.len;
 112         let chars_too_many = if self.config.hard_tabs {
 113             1
 114         } else {
 115             self.config.tab_spaces
 116         };
 117         self.buffer.truncate(total_len - chars_too_many);
 118         self.buffer.push_str("}");
 119         self.block_indent = self.block_indent.block_unindent(self.config);
 120     }
 121
 122     // Note that this only gets called for function definitions. Required methods
 123     // on traits do not get handled here.
 124     fn visit_fn(&mut self,
 125                 fk: visit::FnKind,
 126                 fd: &ast::FnDecl,
 127                 b: &ast::Block,
 128                 s: Span,
 129                 _: ast::NodeId) {
 130         let indent = self.block_indent;
 131         let rewrite = match fk {
 132             visit::FnKind::ItemFn(ident, ref generics, unsafety, constness, abi, vis) => {
 133                 self.rewrite_fn(indent,
 134                                 ident,
 135                                 fd,
 136                                 None,
 137                                 generics,
 138                                 unsafety,
 139                                 constness,
 140                                 abi,
 141                                 vis,
 142                                 codemap::mk_sp(s.lo, b.span.lo),
 143                                 &b)
 144             }
 145             visit::FnKind::Method(ident, ref sig, vis) => {
 146                 self.rewrite_fn(indent,
 147                                 ident,
 148                                 fd,
 149                                 Some(&sig.explicit_self),
 150                                 &sig.generics,
 151                                 sig.unsafety,
 152                                 sig.constness,
 153                                 sig.abi,
 154                                 vis.unwrap_or(ast::Visibility::Inherited),
 155                                 codemap::mk_sp(s.lo, b.span.lo),
 156                                 &b)
 157             }
 158             visit::FnKind::Closure => None,
 159         };
 160
 161         if let Some(fn_str) = rewrite {
 162             self.format_missing_with_indent(s.lo);
 163             self.buffer.push_str(&fn_str);
 164             if let Some(c) = fn_str.chars().last() {
 165                 if c == '}' {
 166                     self.last_pos = b.span.hi;
 167                     return;
 168                 }
 169             }
 170         } else {
 171             self.format_missing(b.span.lo);
 172         }
 173
 174         self.last_pos = b.span.lo;
 175         self.visit_block(b)
 176     }
 177
 178     fn visit_item(&mut self, item: &ast::Item) {
 179         // Don't look at attributes for modules (except for rustfmt_skip).
 180         // We want to avoid looking at attributes in another file, which the AST
 181         // doesn't distinguish.
 182         // FIXME This is overly conservative and means we miss attributes on
 183         // inline modules.
 184         match item.node {
 185             ast::ItemKind::Mod(_) => {
 186                 if utils::contains_skip(&item.attrs) {
 187                     return;
 188                 }
 189             }
 190             _ => {
 191                 if self.visit_attrs(&item.attrs) {
 192                     self.push_rewrite(item.span, None);
 193                     return;
 194                 }
 195             }
 196         }
 197
 198         match item.node {
 199             ast::ItemKind::Use(ref vp) => {
 200                 self.format_import(item.vis, vp, item.span);
 201             }
 202             ast::ItemKind::Impl(..) => {
 203                 self.format_missing_with_indent(item.span.lo);
 204                 if let Some(impl_str) = format_impl(&self.get_context(), item, self.block_indent) {
 205                     self.buffer.push_str(&impl_str);
 206                     self.last_pos = item.span.hi;
 207                 }
 208             }
 209             ast::ItemKind::Trait(..) => {
 210                 self.format_missing_with_indent(item.span.lo);
 211                 if let Some(trait_str) = format_trait(&self.get_context(),
 212                                                       item,
 213                                                       self.block_indent) {
 214                     self.buffer.push_str(&trait_str);
 215                     self.last_pos = item.span.hi;
 216                 }
 217             }
 218             ast::ItemKind::ExternCrate(_) => {
 219                 self.format_missing_with_indent(item.span.lo);
 220                 let new_str = self.snippet(item.span);
 221                 self.buffer.push_str(&new_str);
 222                 self.last_pos = item.span.hi;
 223             }
 224             ast::ItemKind::Struct(ref def, ref generics) => {
 225                 let rewrite = {
 226                     let indent = self.block_indent;
 227                     let context = self.get_context();
 228                     ::items::format_struct(&context,
 229                                            "struct ",
 230                                            item.ident,
 231                                            item.vis,
 232                                            def,
 233                                            Some(generics),
 234                                            item.span,
 235                                            indent)
 236                         .map(|s| {
 237                             match *def {
 238                                 ast::VariantData::Tuple(..) => s + ";",
 239                                 _ => s,
 240                             }
 241                         })
 242                 };
 243                 self.push_rewrite(item.span, rewrite);
 244             }
 245             ast::ItemKind::Enum(ref def, ref generics) => {
 246                 self.format_missing_with_indent(item.span.lo);
 247                 self.visit_enum(item.ident, item.vis, def, generics, item.span);
 248                 self.last_pos = item.span.hi;
 249             }
 250             ast::ItemKind::Mod(ref module) => {
 251                 self.format_missing_with_indent(item.span.lo);
 252                 self.format_mod(module, item.vis, item.span, item.ident);
 253             }
 254             ast::ItemKind::Mac(ref mac) => {
 255                 self.format_missing_with_indent(item.span.lo);
 256                 self.visit_mac(mac, Some(item.ident));
 257             }
 258             ast::ItemKind::ForeignMod(ref foreign_mod) => {
 259                 self.format_missing_with_indent(item.span.lo);
 260                 self.format_foreign_mod(foreign_mod, item.span);
 261             }
 262             ast::ItemKind::Static(ref ty, mutability, ref expr) => {
 263                 let rewrite = rewrite_static("static",
 264                                              item.vis,
 265                                              item.ident,
 266                                              ty,
 267                                              mutability,
 268                                              Some(expr),
 269                                              &self.get_context());
 270                 self.push_rewrite(item.span, rewrite);
 271             }
 272             ast::ItemKind::Const(ref ty, ref expr) => {
 273                 let rewrite = rewrite_static("const",
 274                                              item.vis,
 275                                              item.ident,
 276                                              ty,
 277                                              ast::Mutability::Immutable,
 278                                              Some(expr),
 279                                              &self.get_context());
 280                 self.push_rewrite(item.span, rewrite);
 281             }
 282             ast::ItemKind::DefaultImpl(..) => {
 283                 // FIXME(#78): format impl definitions.
 284             }
 285             ast::ItemKind::Fn(ref decl, unsafety, constness, abi, ref generics, ref body) => {
 286                 self.visit_fn(visit::FnKind::ItemFn(item.ident,
 287                                                     generics,
 288                                                     unsafety,
 289                                                     constness,
 290                                                     abi,
 291                                                     item.vis),
 292                               decl,
 293                               body,
 294                               item.span,
 295                               item.id)
 296             }
 297             ast::ItemKind::Ty(ref ty, ref generics) => {
 298                 let rewrite = rewrite_type_alias(&self.get_context(),
 299                                                  self.block_indent,
 300                                                  item.ident,
 301                                                  ty,
 302                                                  generics,
 303                                                  item.vis,
 304                                                  item.span);
 305                 self.push_rewrite(item.span, rewrite);
 306             }
 307         }
 308     }
 309
 310     pub fn visit_trait_item(&mut self, ti: &ast::TraitItem) {
 311         if self.visit_attrs(&ti.attrs) {
 312             return;
 313         }
 314
 315         match ti.node {
 316             ast::TraitItemKind::Const(ref ty, ref expr_opt) => {
 317                 let rewrite = rewrite_static("const",
 318                                              ast::Visibility::Inherited,
 319                                              ti.ident,
 320                                              ty,
 321                                              ast::Mutability::Immutable,
 322                                              expr_opt.as_ref(),
 323                                              &self.get_context());
 324                 self.push_rewrite(ti.span, rewrite);
 325             }
 326             ast::TraitItemKind::Method(ref sig, None) => {
 327                 let indent = self.block_indent;
 328                 let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, ti.span);
 329                 self.push_rewrite(ti.span, rewrite);
 330             }
 331             ast::TraitItemKind::Method(ref sig, Some(ref body)) => {
 332                 self.visit_fn(visit::FnKind::Method(ti.ident, sig, None),
 333                               &sig.decl,
 334                               &body,
 335                               ti.span,
 336                               ti.id);
 337             }
 338             ast::TraitItemKind::Type(ref type_param_bounds, _) => {
 339                 let rewrite = rewrite_associated_type(ti.ident,
 340                                                       None,
 341                                                       Some(type_param_bounds),
 342                                                       &self.get_context(),
 343                                                       self.block_indent);
 344                 self.push_rewrite(ti.span, rewrite);
 345             }
 346         }
 347     }
 348
 349     pub fn visit_impl_item(&mut self, ii: &ast::ImplItem) {
 350         if self.visit_attrs(&ii.attrs) {
 351             return;
 352         }
 353
 354         match ii.node {
 355             ast::ImplItemKind::Method(ref sig, ref body) => {
 356                 self.visit_fn(visit::FnKind::Method(ii.ident, sig, Some(ii.vis)),
 357                               &sig.decl,
 358                               body,
 359                               ii.span,
 360                               ii.id);
 361             }
 362             ast::ImplItemKind::Const(ref ty, ref expr) => {
 363                 let rewrite = rewrite_static("const",
 364                                              ast::Visibility::Inherited,
 365                                              ii.ident,
 366                                              ty,
 367                                              ast::Mutability::Immutable,
 368                                              Some(expr),
 369                                              &self.get_context());
 370                 self.push_rewrite(ii.span, rewrite);
 371             }
 372             ast::ImplItemKind::Type(ref ty) => {
 373                 let rewrite = rewrite_associated_type(ii.ident,
 374                                                       Some(ty),
 375                                                       None,
 376                                                       &self.get_context(),
 377                                                       self.block_indent);
 378                 self.push_rewrite(ii.span, rewrite);
 379             }
 380             ast::ImplItemKind::Macro(ref mac) => {
 381                 self.format_missing_with_indent(ii.span.lo);
 382                 self.visit_mac(mac, Some(ii.ident));
 383             }
 384         }
 385     }
 386
 387     fn visit_mac(&mut self, mac: &ast::Mac, ident: Option<ast::Ident>) {
 388         // 1 = ;
 389         let width = self.config.max_width - self.block_indent.width() - 1;
 390         let rewrite = rewrite_macro(mac, ident, &self.get_context(), width, self.block_indent);
 391
 392         if let Some(res) = rewrite {
 393             self.buffer.push_str(&res);
 394             self.last_pos = mac.span.hi;
 395         }
 396     }
 397
 398     fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
 399         self.format_missing_with_indent(span.lo);
 400         let result = rewrite.unwrap_or_else(|| self.snippet(span));
 401         self.buffer.push_str(&result);
 402         self.last_pos = span.hi;
 403     }
 404
 405     pub fn from_codemap(parse_session: &'a ParseSess, config: &'a Config) -> FmtVisitor<'a> {
 406         FmtVisitor {
 407             parse_session: parse_session,
 408             codemap: parse_session.codemap(),
 409             buffer: StringBuffer::new(),
 410             last_pos: BytePos(0),
 411             block_indent: Indent {
 412                 block_indent: 0,
 413                 alignment: 0,
 414             },
 415             config: config,
 416         }
 417     }
 418
 419     pub fn snippet(&self, span: Span) -> String {
 420         match self.codemap.span_to_snippet(span) {
 421             Ok(s) => s,
 422             Err(_) => {
 423                 println!("Couldn't make snippet for span {:?}->{:?}",
 424                          self.codemap.lookup_char_pos(span.lo),
 425                          self.codemap.lookup_char_pos(span.hi));
 426                 "".to_owned()
 427             }
 428         }
 429     }
 430
 431     // Returns true if we should skip the following item.
 432     pub fn visit_attrs(&mut self, attrs: &[ast::Attribute]) -> bool {
 433         if utils::contains_skip(attrs) {
 434             return true;
 435         }
 436
 437         let outers: Vec<_> = attrs.iter()
 438                                   .filter(|a| a.node.style == ast::AttrStyle::Outer)
 439                                   .cloned()
 440                                   .collect();
 441         if outers.is_empty() {
 442             return false;
 443         }
 444
 445         let first = &outers[0];
 446         self.format_missing_with_indent(first.span.lo);
 447
 448         let rewrite = outers.rewrite(&self.get_context(),
 449                                      self.config.max_width - self.block_indent.width(),
 450                                      self.block_indent)
 451                             .unwrap();
 452         self.buffer.push_str(&rewrite);
 453         let last = outers.last().unwrap();
 454         self.last_pos = last.span.hi;
 455         false
 456     }
 457
 458     fn walk_mod_items(&mut self, m: &ast::Mod) {
 459         for item in &m.items {
 460             self.visit_item(&item);
 461         }
 462     }
 463
 464     fn format_mod(&mut self, m: &ast::Mod, vis: ast::Visibility, s: Span, ident: ast::Ident) {
 465         // Decide whether this is an inline mod or an external mod.
 466         let local_file_name = self.codemap.span_to_filename(s);
 467         let is_internal = local_file_name == self.codemap.span_to_filename(m.inner);
 468
 469         self.buffer.push_str(utils::format_visibility(vis));
 470         self.buffer.push_str("mod ");
 471         self.buffer.push_str(&ident.to_string());
 472
 473         if is_internal {
 474             self.buffer.push_str(" {");
 475             // Hackery to account for the closing }.
 476             let mod_lo = self.codemap.span_after(s, "{");
 477             let body_snippet = self.snippet(codemap::mk_sp(mod_lo, m.inner.hi - BytePos(1)));
 478             let body_snippet = body_snippet.trim();
 479             if body_snippet.is_empty() {
 480                 self.buffer.push_str("}");
 481             } else {
 482                 self.last_pos = mod_lo;
 483                 self.block_indent = self.block_indent.block_indent(self.config);
 484                 self.walk_mod_items(m);
 485                 self.format_missing_with_indent(m.inner.hi - BytePos(1));
 486                 self.close_block();
 487             }
 488             self.last_pos = m.inner.hi;
 489         } else {
 490             self.buffer.push_str(";");
 491             self.last_pos = s.hi;
 492         }
 493     }
 494
 495     pub fn format_separate_mod(&mut self, m: &ast::Mod) {
 496         let filemap = self.codemap.lookup_char_pos(m.inner.lo).file;
 497         self.last_pos = filemap.start_pos;
 498         self.block_indent = Indent::empty();
 499         self.walk_mod_items(m);
 500         self.format_missing(filemap.end_pos);
 501     }
 502
 503     fn format_import(&mut self, vis: ast::Visibility, vp: &ast::ViewPath, span: Span) {
 504         let vis = utils::format_visibility(vis);
 505         let mut offset = self.block_indent;
 506         offset.alignment += vis.len() + "use ".len();
 507         // 1 = ";"
 508         match vp.rewrite(&self.get_context(),
 509                          self.config.max_width - offset.width() - 1,
 510                          offset) {
 511             Some(ref s) if s.is_empty() => {
 512                 // Format up to last newline
 513                 let prev_span = codemap::mk_sp(self.last_pos, span.lo);
 514                 let span_end = match self.snippet(prev_span).rfind('\n') {
 515                     Some(offset) => self.last_pos + BytePos(offset as u32),
 516                     None => span.lo,
 517                 };
 518                 self.format_missing(span_end);
 519                 self.last_pos = span.hi;
 520             }
 521             Some(ref s) => {
 522                 let s = format!("{}use {};", vis, s);
 523                 self.format_missing_with_indent(span.lo);
 524                 self.buffer.push_str(&s);
 525                 self.last_pos = span.hi;
 526             }
 527             None => {
 528                 self.format_missing_with_indent(span.lo);
 529                 self.format_missing(span.hi);
 530             }
 531         }
 532     }
 533
 534     pub fn get_context(&self) -> RewriteContext {
 535         RewriteContext {
 536             parse_session: self.parse_session,
 537             codemap: self.codemap,
 538             config: self.config,
 539             block_indent: self.block_indent,
 540         }
 541     }
 542 }
 543
 544 impl<'a> Rewrite for [ast::Attribute] {
 545     fn rewrite(&self, context: &RewriteContext, _: usize, offset: Indent) -> Option<String> {
 546         let mut result = String::new();
 547         if self.is_empty() {
 548             return Some(result);
 549         }
 550         let indent = offset.to_string(context.config);
 551
 552         for (i, a) in self.iter().enumerate() {
 553             let a_str = context.snippet(a.span);
 554
 555             // Write comments and blank lines between attributes.
 556             if i > 0 {
 557                 let comment = context.snippet(codemap::mk_sp(self[i - 1].span.hi, a.span.lo));
 558                 // This particular horror show is to preserve line breaks in between doc
 559                 // comments. An alternative would be to force such line breaks to start
 560                 // with the usual doc comment token.
 561                 let multi_line = a_str.starts_with("//") && comment.matches('\n').count() > 1;
 562                 let comment = comment.trim();
 563                 if !comment.is_empty() {
 564                     let comment = try_opt!(rewrite_comment(comment,
 565                                                            false,
 566                                                            context.config.max_width -
 567                                                            offset.width(),
 568                                                            offset,
 569                                                            context.config));
 570                     result.push_str(&indent);
 571                     result.push_str(&comment);
 572                     result.push('\n');
 573                 } else if multi_line {
 574                     result.push('\n');
 575                 }
 576                 result.push_str(&indent);
 577             }
 578
 579             // Write the attribute itself.
 580             result.push_str(&a_str);
 581
 582             if i < self.len() - 1 {
 583                 result.push('\n');
 584             }
 585         }
 586
 587         Some(result)
 588     }
 589 }