src/librustdoc/html/highlight.rs

   1 // Copyright 2014-2016 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 //! Basic syntax highlighting functionality.
  12 //!
  13 //! This module uses libsyntax's lexer to provide token-based highlighting for
  14 //! the HTML documentation generated by rustdoc.
  15 //!
  16 //! If you just want to syntax highlighting for a Rust program, then you can use
  17 //! the `render_inner_with_highlighting` or `render_with_highlighting`
  18 //! functions. For more advanced use cases (if you want to supply your own css
  19 //! classes or control how the HTML is generated, or even generate something
  20 //! other then HTML), then you should implement the `Writer` trait and use a
  21 //! `Classifier`.
  22
  23 use html::escape::Escape;
  24
  25 use std::fmt::Display;
  26 use std::io;
  27 use std::io::prelude::*;
  28
  29 use syntax::codemap::{CodeMap, FilePathMapping};
  30 use syntax::parse::lexer::{self, TokenAndSpan};
  31 use syntax::parse::token;
  32 use syntax::parse;
  33 use syntax_pos::Span;
  34
  35 /// Highlights `src`, returning the HTML output.
  36 pub fn render_with_highlighting(src: &str, class: Option<&str>, id: Option<&str>,
  37                                 extension: Option<&str>,
  38                                 tooltip: Option<(&str, &str)>) -> String {
  39     debug!("highlighting: ================\n{}\n==============", src);
  40     let sess = parse::ParseSess::new(FilePathMapping::empty());
  41     let fm = sess.codemap().new_filemap("<stdin>".to_string(), src.to_string());
  42
  43     let mut out = Vec::new();
  44     if let Some((tooltip, class)) = tooltip {
  45         write!(out, "<div class='information'><div class='tooltip {}'>ⓘ<span \
  46                      class='tooltiptext'>{}</span></div></div>",
  47                class, tooltip).unwrap();
  48     }
  49     write_header(class, id, &mut out).unwrap();
  50
  51     let mut classifier = Classifier::new(lexer::StringReader::new(&sess, fm), sess.codemap());
  52     if let Err(_) = classifier.write_source(&mut out) {
  53         return format!("<pre>{}</pre>", src);
  54     }
  55
  56     if let Some(extension) = extension {
  57         write!(out, "{}", extension).unwrap();
  58     }
  59     write_footer(&mut out).unwrap();
  60     String::from_utf8_lossy(&out[..]).into_owned()
  61 }
  62
  63 /// Highlights `src`, returning the HTML output. Returns only the inner html to
  64 /// be inserted into an element. C.f., `render_with_highlighting` which includes
  65 /// an enclosing `<pre>` block.
  66 pub fn render_inner_with_highlighting(src: &str) -> io::Result<String> {
  67     let sess = parse::ParseSess::new(FilePathMapping::empty());
  68     let fm = sess.codemap().new_filemap("<stdin>".to_string(), src.to_string());
  69
  70     let mut out = Vec::new();
  71     let mut classifier = Classifier::new(lexer::StringReader::new(&sess, fm), sess.codemap());
  72     classifier.write_source(&mut out)?;
  73
  74     Ok(String::from_utf8_lossy(&out).into_owned())
  75 }
  76
  77 /// Processes a program (nested in the internal `lexer`), classifying strings of
  78 /// text by highlighting category (`Class`). Calls out to a `Writer` to write
  79 /// each span of text in sequence.
  80 pub struct Classifier<'a> {
  81     lexer: lexer::StringReader<'a>,
  82     codemap: &'a CodeMap,
  83
  84     // State of the classifier.
  85     in_attribute: bool,
  86     in_macro: bool,
  87     in_macro_nonterminal: bool,
  88 }
  89
  90 /// How a span of text is classified. Mostly corresponds to token kinds.
  91 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
  92 pub enum Class {
  93     None,
  94     Comment,
  95     DocComment,
  96     Attribute,
  97     KeyWord,
  98     // Keywords that do pointer/reference stuff.
  99     RefKeyWord,
 100     Self_,
 101     Op,
 102     Macro,
 103     MacroNonTerminal,
 104     String,
 105     Number,
 106     Bool,
 107     Ident,
 108     Lifetime,
 109     PreludeTy,
 110     PreludeVal,
 111     QuestionMark,
 112 }
 113
 114 /// Trait that controls writing the output of syntax highlighting. Users should
 115 /// implement this trait to customize writing output.
 116 ///
 117 /// The classifier will call into the `Writer` implementation as it finds spans
 118 /// of text to highlight. Exactly how that text should be highlighted is up to
 119 /// the implementation.
 120 pub trait Writer {
 121     /// Called when we start processing a span of text that should be highlighted.
 122     /// The `Class` argument specifies how it should be highlighted.
 123     fn enter_span(&mut self, _: Class) -> io::Result<()>;
 124
 125     /// Called at the end of a span of highlighted text.
 126     fn exit_span(&mut self) -> io::Result<()>;
 127
 128     /// Called for a span of text, usually, but not always, a single token. If
 129     /// the string of text (`T`) does correspond to a token, then the token will
 130     /// also be passed. If the text should be highlighted differently from the
 131     /// surrounding text, then the `Class` argument will be a value other than
 132     /// `None`.
 133     /// The following sequences of callbacks are equivalent:
 134     /// ```plain
 135     ///     enter_span(Foo), string("text", None), exit_span()
 136     ///     string("text", Foo)
 137     /// ```
 138     /// The latter can be thought of as a shorthand for the former, which is
 139     /// more flexible.
 140     fn string<T: Display>(&mut self,
 141                           text: T,
 142                           klass: Class,
 143                           tok: Option<&TokenAndSpan>)
 144                           -> io::Result<()>;
 145 }
 146
 147 // Implement `Writer` for anthing that can be written to, this just implements
 148 // the default rustdoc behaviour.
 149 impl<U: Write> Writer for U {
 150     fn string<T: Display>(&mut self,
 151                           text: T,
 152                           klass: Class,
 153                           _tas: Option<&TokenAndSpan>)
 154                           -> io::Result<()> {
 155         match klass {
 156             Class::None => write!(self, "{}", text),
 157             klass => write!(self, "<span class=\"{}\">{}</span>", klass.rustdoc_class(), text),
 158         }
 159     }
 160
 161     fn enter_span(&mut self, klass: Class) -> io::Result<()> {
 162         write!(self, "<span class=\"{}\">", klass.rustdoc_class())
 163     }
 164
 165     fn exit_span(&mut self) -> io::Result<()> {
 166         write!(self, "</span>")
 167     }
 168 }
 169
 170 impl<'a> Classifier<'a> {
 171     pub fn new(lexer: lexer::StringReader<'a>, codemap: &'a CodeMap) -> Classifier<'a> {
 172         Classifier {
 173             lexer,
 174             codemap,
 175             in_attribute: false,
 176             in_macro: false,
 177             in_macro_nonterminal: false,
 178         }
 179     }
 180
 181     /// Gets the next token out of the lexer, emitting fatal errors if lexing fails.
 182     fn try_next_token(&mut self) -> io::Result<TokenAndSpan> {
 183         match self.lexer.try_next_token() {
 184             Ok(tas) => Ok(tas),
 185             Err(_) => {
 186                 self.lexer.emit_fatal_errors();
 187                 self.lexer.sess.span_diagnostic
 188                     .struct_warn("Backing out of syntax highlighting")
 189                     .note("You probably did not intend to render this as a rust code-block")
 190                     .emit();
 191                 Err(io::Error::new(io::ErrorKind::Other, ""))
 192             }
 193         }
 194     }
 195
 196     /// Exhausts the `lexer` writing the output into `out`.
 197     ///
 198     /// The general structure for this method is to iterate over each token,
 199     /// possibly giving it an HTML span with a class specifying what flavor of token
 200     /// is used. All source code emission is done as slices from the source map,
 201     /// not from the tokens themselves, in order to stay true to the original
 202     /// source.
 203     pub fn write_source<W: Writer>(&mut self,
 204                                    out: &mut W)
 205                                    -> io::Result<()> {
 206         loop {
 207             let next = self.try_next_token()?;
 208             if next.tok == token::Eof {
 209                 break;
 210             }
 211
 212             self.write_token(out, next)?;
 213         }
 214
 215         Ok(())
 216     }
 217
 218     // Handles an individual token from the lexer.
 219     fn write_token<W: Writer>(&mut self,
 220                               out: &mut W,
 221                               tas: TokenAndSpan)
 222                               -> io::Result<()> {
 223         let klass = match tas.tok {
 224             token::Shebang(s) => {
 225                 out.string(Escape(&s.as_str()), Class::None, Some(&tas))?;
 226                 return Ok(());
 227             },
 228
 229             token::Whitespace => Class::None,
 230             token::Comment => Class::Comment,
 231             token::DocComment(..) => Class::DocComment,
 232
 233             // If this '&' or '*' token is followed by a non-whitespace token, assume that it's the
 234             // reference or dereference operator or a reference or pointer type, instead of the
 235             // bit-and or multiplication operator.
 236             token::BinOp(token::And) | token::BinOp(token::Star)
 237                 if self.lexer.peek().tok != token::Whitespace => Class::RefKeyWord,
 238
 239             // Consider this as part of a macro invocation if there was a
 240             // leading identifier.
 241             token::Not if self.in_macro => {
 242                 self.in_macro = false;
 243                 Class::Macro
 244             }
 245
 246             // Operators.
 247             token::Eq | token::Lt | token::Le | token::EqEq | token::Ne | token::Ge | token::Gt |
 248                 token::AndAnd | token::OrOr | token::Not | token::BinOp(..) | token::RArrow |
 249                 token::BinOpEq(..) | token::FatArrow => Class::Op,
 250
 251             // Miscellaneous, no highlighting.
 252             token::Dot | token::DotDot | token::DotDotDot | token::DotDotEq | token::Comma |
 253                 token::Semi | token::Colon | token::ModSep | token::LArrow | token::OpenDelim(_) |
 254                 token::CloseDelim(token::Brace) | token::CloseDelim(token::Paren) |
 255                 token::CloseDelim(token::NoDelim) => Class::None,
 256
 257             token::Question => Class::QuestionMark,
 258
 259             token::Dollar => {
 260                 if self.lexer.peek().tok.is_ident() {
 261                     self.in_macro_nonterminal = true;
 262                     Class::MacroNonTerminal
 263                 } else {
 264                     Class::None
 265                 }
 266             }
 267
 268             // This might be the start of an attribute. We're going to want to
 269             // continue highlighting it as an attribute until the ending ']' is
 270             // seen, so skip out early. Down below we terminate the attribute
 271             // span when we see the ']'.
 272             token::Pound => {
 273                 // We can't be sure that our # begins an attribute (it could
 274                 // just be appearing in a macro) until we read either `#![` or
 275                 // `#[` from the input stream.
 276                 //
 277                 // We don't want to start highlighting as an attribute until
 278                 // we're confident there is going to be a ] coming up, as
 279                 // otherwise # tokens in macros highlight the rest of the input
 280                 // as an attribute.
 281
 282                 // Case 1: #![inner_attribute]
 283                 if self.lexer.peek().tok == token::Not {
 284                     self.try_next_token()?; // NOTE: consumes `!` token!
 285                     if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
 286                         self.in_attribute = true;
 287                         out.enter_span(Class::Attribute)?;
 288                     }
 289                     out.string("#", Class::None, None)?;
 290                     out.string("!", Class::None, None)?;
 291                     return Ok(());
 292                 }
 293
 294                 // Case 2: #[outer_attribute]
 295                 if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
 296                     self.in_attribute = true;
 297                     out.enter_span(Class::Attribute)?;
 298                 }
 299                 out.string("#", Class::None, None)?;
 300                 return Ok(());
 301             }
 302             token::CloseDelim(token::Bracket) => {
 303                 if self.in_attribute {
 304                     self.in_attribute = false;
 305                     out.string("]", Class::None, None)?;
 306                     out.exit_span()?;
 307                     return Ok(());
 308                 } else {
 309                     Class::None
 310                 }
 311             }
 312
 313             token::Literal(lit, _suf) => {
 314                 match lit {
 315                     // Text literals.
 316                     token::Byte(..) | token::Char(..) |
 317                         token::ByteStr(..) | token::ByteStrRaw(..) |
 318                         token::Str_(..) | token::StrRaw(..) => Class::String,
 319
 320                     // Number literals.
 321                     token::Integer(..) | token::Float(..) => Class::Number,
 322                 }
 323             }
 324
 325             // Keywords are also included in the identifier set.
 326             token::Ident(ident) => {
 327                 match &*ident.name.as_str() {
 328                     "ref" | "mut" => Class::RefKeyWord,
 329
 330                     "self" |"Self" => Class::Self_,
 331                     "false" | "true" => Class::Bool,
 332
 333                     "Option" | "Result" => Class::PreludeTy,
 334                     "Some" | "None" | "Ok" | "Err" => Class::PreludeVal,
 335
 336                     "$crate" => Class::KeyWord,
 337                     _ if tas.tok.is_reserved_ident() => Class::KeyWord,
 338
 339                     _ => {
 340                         if self.in_macro_nonterminal {
 341                             self.in_macro_nonterminal = false;
 342                             Class::MacroNonTerminal
 343                         } else if self.lexer.peek().tok == token::Not {
 344                             self.in_macro = true;
 345                             Class::Macro
 346                         } else {
 347                             Class::Ident
 348                         }
 349                     }
 350                 }
 351             }
 352
 353             token::Lifetime(..) => Class::Lifetime,
 354
 355             token::Underscore | token::Eof | token::Interpolated(..) |
 356             token::Tilde | token::At | token::DotEq => Class::None,
 357         };
 358
 359         // Anything that didn't return above is the simple case where we the
 360         // class just spans a single token, so we can use the `string` method.
 361         out.string(Escape(&self.snip(tas.sp)), klass, Some(&tas))
 362     }
 363
 364     // Helper function to get a snippet from the codemap.
 365     fn snip(&self, sp: Span) -> String {
 366         self.codemap.span_to_snippet(sp).unwrap()
 367     }
 368 }
 369
 370 impl Class {
 371     /// Returns the css class expected by rustdoc for each `Class`.
 372     pub fn rustdoc_class(self) -> &'static str {
 373         match self {
 374             Class::None => "",
 375             Class::Comment => "comment",
 376             Class::DocComment => "doccomment",
 377             Class::Attribute => "attribute",
 378             Class::KeyWord => "kw",
 379             Class::RefKeyWord => "kw-2",
 380             Class::Self_ => "self",
 381             Class::Op => "op",
 382             Class::Macro => "macro",
 383             Class::MacroNonTerminal => "macro-nonterminal",
 384             Class::String => "string",
 385             Class::Number => "number",
 386             Class::Bool => "bool-val",
 387             Class::Ident => "ident",
 388             Class::Lifetime => "lifetime",
 389             Class::PreludeTy => "prelude-ty",
 390             Class::PreludeVal => "prelude-val",
 391             Class::QuestionMark => "question-mark"
 392         }
 393     }
 394 }
 395
 396 fn write_header(class: Option<&str>,
 397                 id: Option<&str>,
 398                 out: &mut Write)
 399                 -> io::Result<()> {
 400     write!(out, "<pre ")?;
 401     if let Some(id) = id {
 402         write!(out, "id='{}' ", id)?;
 403     }
 404     write!(out, "class=\"rust {}\">\n", class.unwrap_or(""))
 405 }
 406
 407 fn write_footer(out: &mut Write) -> io::Result<()> {
 408     write!(out, "</pre>\n")
 409 }