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Don't highlight # which does not start an attribute in rustdoc #43918

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Aug 30, 2017
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58 changes: 43 additions & 15 deletions src/librustdoc/html/highlight.rs
Original file line number Diff line number Diff line change
Expand Up @@ -172,6 +172,21 @@ impl<'a> Classifier<'a> {
}
}

/// Gets the next token out of the lexer, emitting fatal errors if lexing fails.
fn try_next_token(&mut self) -> io::Result<TokenAndSpan> {
match self.lexer.try_next_token() {
Ok(tas) => Ok(tas),
Err(_) => {
self.lexer.emit_fatal_errors();
self.lexer.sess.span_diagnostic
.struct_warn("Backing out of syntax highlighting")
.note("You probably did not intend to render this as a rust code-block")
.emit();
Err(io::Error::new(io::ErrorKind::Other, ""))
}
}
}

/// Exhausts the `lexer` writing the output into `out`.
///
/// The general structure for this method is to iterate over each token,
Expand All @@ -183,18 +198,7 @@ impl<'a> Classifier<'a> {
out: &mut W)
-> io::Result<()> {
loop {
let next = match self.lexer.try_next_token() {
Ok(tas) => tas,
Err(_) => {
self.lexer.emit_fatal_errors();
self.lexer.sess.span_diagnostic
.struct_warn("Backing out of syntax highlighting")
.note("You probably did not intend to render this as a rust code-block")
.emit();
return Err(io::Error::new(io::ErrorKind::Other, ""));
}
};

let next = self.try_next_token()?;
if next.tok == token::Eof {
break;
}
Expand Down Expand Up @@ -255,13 +259,37 @@ impl<'a> Classifier<'a> {
}
}

// This is the start of an attribute. We're going to want to
// This might be the start of an attribute. We're going to want to
// continue highlighting it as an attribute until the ending ']' is
// seen, so skip out early. Down below we terminate the attribute
// span when we see the ']'.
token::Pound => {
self.in_attribute = true;
out.enter_span(Class::Attribute)?;
// We can't be sure that our # begins an attribute (it could
// just be appearing in a macro) until we read either `#![` or
// `#[` from the input stream.
//
// We don't want to start highlighting as an attribute until
// we're confident there is going to be a ] coming up, as
// otherwise # tokens in macros highlight the rest of the input
// as an attribute.

// Case 1: #![inner_attribute]
if self.lexer.peek().tok == token::Not {
self.try_next_token()?; // NOTE: consumes `!` token!
if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
self.in_attribute = true;
out.enter_span(Class::Attribute)?;
}
out.string("#", Class::None, None)?;
out.string("!", Class::None, None)?;
return Ok(());
}

// Case 2: #[outer_attribute]
if self.lexer.peek().tok == token::OpenDelim(token::Bracket) {
self.in_attribute = true;
out.enter_span(Class::Attribute)?;
}
out.string("#", Class::None, None)?;
return Ok(());
}
Expand Down
8 changes: 6 additions & 2 deletions src/test/rustdoc/issue-41783.rs
Original file line number Diff line number Diff line change
Expand Up @@ -12,14 +12,18 @@
// @!has - 'space'
// @!has - 'comment'
// @has - '# <span class="ident">single'
// @has - '#<span class="attribute"># <span class="ident">double</span>'
// @has - '#<span class="attribute">#<span class="attribute"># <span class="ident">triple</span>'
// @has - '## <span class="ident">double</span>'
// @has - '### <span class="ident">triple</span>'
// @has - '<span class="attribute">#[<span class="ident">outer</span>]</span>'
// @has - '<span class="attribute">#![<span class="ident">inner</span>]</span>'

/// ```no_run
/// # # space
/// # comment
/// ## single
/// ### double
/// #### triple
/// ##[outer]
/// ##![inner]
/// ```
pub struct Foo;