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.
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.
11 //! Basic syntax highlighting functionality.
13 //! This module uses libsyntax's lexer to provide token-based highlighting for
14 //! the HTML documentation generated by rustdoc.
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
23 use html::escape::Escape;
25 use std::fmt::Display;
27 use std::io::prelude::*;
29 use syntax::codemap::{CodeMap, FilePathMapping};
30 use syntax::parse::lexer::{self, TokenAndSpan};
31 use syntax::parse::token;
33 use syntax_pos::{Span, FileName};
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(FileName::Custom("stdin".to_string()), src.to_string());
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();
49 write_header(class, id, &mut out).unwrap();
51 let mut classifier = Classifier::new(lexer::StringReader::new(&sess, fm, None), sess.codemap());
52 if let Err(_) = classifier.write_source(&mut out) {
53 return format!("<pre>{}</pre>", src);
56 if let Some(extension) = extension {
57 write!(out, "{}", extension).unwrap();
59 write_footer(&mut out).unwrap();
60 String::from_utf8_lossy(&out[..]).into_owned()
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(FileName::Custom("stdin".to_string()), src.to_string());
70 let mut out = Vec::new();
71 let mut classifier = Classifier::new(lexer::StringReader::new(&sess, fm, None), sess.codemap());
72 classifier.write_source(&mut out)?;
74 Ok(String::from_utf8_lossy(&out).into_owned())
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>,
84 // State of the classifier.
87 in_macro_nonterminal: bool,
90 /// How a span of text is classified. Mostly corresponds to token kinds.
91 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
98 // Keywords that do pointer/reference stuff.
114 /// Trait that controls writing the output of syntax highlighting. Users should
115 /// implement this trait to customize writing output.
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.
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<()>;
125 /// Called at the end of a span of highlighted text.
126 fn exit_span(&mut self) -> io::Result<()>;
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
133 /// The following sequences of callbacks are equivalent:
135 /// enter_span(Foo), string("text", None), exit_span()
136 /// string("text", Foo)
138 /// The latter can be thought of as a shorthand for the former, which is
140 fn string<T: Display>(&mut self,
143 tok: Option<&TokenAndSpan>)
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,
153 _tas: Option<&TokenAndSpan>)
156 Class::None => write!(self, "{}", text),
157 klass => write!(self, "<span class=\"{}\">{}</span>", klass.rustdoc_class(), text),
161 fn enter_span(&mut self, klass: Class) -> io::Result<()> {
162 write!(self, "<span class=\"{}\">", klass.rustdoc_class())
165 fn exit_span(&mut self) -> io::Result<()> {
166 write!(self, "</span>")
170 impl<'a> Classifier<'a> {
171 pub fn new(lexer: lexer::StringReader<'a>, codemap: &'a CodeMap) -> Classifier<'a> {
177 in_macro_nonterminal: false,
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() {
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")
191 Err(io::Error::new(io::ErrorKind::Other, ""))
196 /// Exhausts the `lexer` writing the output into `out`.
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
203 pub fn write_source<W: Writer>(&mut self,
207 let next = self.try_next_token()?;
208 if next.tok == token::Eof {
212 self.write_token(out, next)?;
218 // Handles an individual token from the lexer.
219 fn write_token<W: Writer>(&mut self,
223 let klass = match tas.tok {
224 token::Shebang(s) => {
225 out.string(Escape(&s.as_str()), Class::None, Some(&tas))?;
229 token::Whitespace => Class::None,
230 token::Comment => Class::Comment,
231 token::DocComment(..) => Class::DocComment,
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,
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;
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,
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,
257 token::Question => Class::QuestionMark,
260 if self.lexer.peek().tok.is_ident() {
261 self.in_macro_nonterminal = true;
262 Class::MacroNonTerminal
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 ']'.
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.
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
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)?;
289 out.string("#", Class::None, None)?;
290 out.string("!", Class::None, None)?;
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)?;
299 out.string("#", Class::None, None)?;
302 token::CloseDelim(token::Bracket) => {
303 if self.in_attribute {
304 self.in_attribute = false;
305 out.string("]", Class::None, None)?;
313 token::Literal(lit, _suf) => {
316 token::Byte(..) | token::Char(..) |
317 token::ByteStr(..) | token::ByteStrRaw(..) |
318 token::Str_(..) | token::StrRaw(..) => Class::String,
321 token::Integer(..) | token::Float(..) => Class::Number,
325 // Keywords are also included in the identifier set.
326 token::Ident(ident, is_raw) => {
327 match &*ident.as_str() {
328 "ref" | "mut" if !is_raw => Class::RefKeyWord,
330 "self" | "Self" => Class::Self_,
331 "false" | "true" if !is_raw => Class::Bool,
333 "Option" | "Result" => Class::PreludeTy,
334 "Some" | "None" | "Ok" | "Err" => Class::PreludeVal,
336 "$crate" => Class::KeyWord,
337 _ if tas.tok.is_reserved_ident() => Class::KeyWord,
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;
353 token::Lifetime(..) => Class::Lifetime,
355 token::Eof | token::Interpolated(..) |
356 token::Tilde | token::At | token::DotEq | token::SingleQuote => Class::None,
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))
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()
371 /// Returns the css class expected by rustdoc for each `Class`.
372 pub fn rustdoc_class(self) -> &'static str {
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",
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"
396 fn write_header(class: Option<&str>,
400 write!(out, "<pre ")?;
401 if let Some(id) = id {
402 write!(out, "id='{}' ", id)?;
404 write!(out, "class=\"rust {}\">\n", class.unwrap_or(""))
407 fn write_footer(out: &mut dyn Write) -> io::Result<()> {
408 write!(out, "</pre>\n")