Auto merge of #53933 - GuillaumeGomez:codeblock-error-display, r=Quie…

…tMisdreavus

Improve error display for codeblocks in rustdoc

Part of #53919.

r? @QuietMisdreavus

src/librustdoc/html/highlight.rs

@@ -44,9 +44,21 @@ pub fn render_with_highlighting(src: &str, class: Option<&str>,
  }
  write_header(class, &mut out).unwrap();
 
- let mut classifier = Classifier::new(lexer::StringReader::new(&sess, fm, None),
- sess.source_map());
+ let lexer = match lexer::StringReader::new_without_err(&sess, fm, None, "Output from rustc:") {
+ Ok(l) => l,
+ Err(_) => {
+ let first_line = src.lines().next().unwrap_or_else(|| "");
+ let mut err = sess.span_diagnostic
+ .struct_warn(&format!("Invalid doc comment starting with: `{}`\n\
+ (Ignoring this codeblock)",
+ first_line));
+ err.emit();
+ return String::new();
+ }
+ };
+ let mut classifier = Classifier::new(lexer, sess.source_map());
  if classifier.write_source(&mut out).is_err() {
+ classifier.lexer.emit_fatal_errors();
  return format!("<pre>{}</pre>", src);
  }
 
@@ -162,11 +174,10 @@ impl<'a> Classifier<'a> {
  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();
+ let mut err = self.lexer.sess.span_diagnostic
+ .struct_warn("Backing out of syntax highlighting");
+ err.note("You probably did not intend to render this as a rust code-block");
+ err.emit();
  Err(io::Error::new(io::ErrorKind::Other, ""))
  }
  }

src/libsyntax/parse/lexer/mod.rs

@@ -238,6 +238,19 @@ impl<'a> StringReader<'a> {
  sr
  }
 
+ pub fn new_without_err(sess: &'a ParseSess,
+ source_file: Lrc<syntax_pos::SourceFile>,
+ override_span: Option<Span>,
+ prepend_error_text: &str) -> Result<Self, ()> {
+ let mut sr = StringReader::new_raw(sess, source_file, override_span);
+ if sr.advance_token().is_err() {
+ eprintln!("{}", prepend_error_text);
+ sr.emit_fatal_errors();
+ return Err(());
+ }
+ Ok(sr)
+ }
+
  pub fn retokenize(sess: &'a ParseSess, mut span: Span) -> Self {
  let begin = sess.source_map().lookup_byte_offset(span.lo());
  let end = sess.source_map().lookup_byte_offset(span.hi());

src/test/rustdoc-ui/invalid-syntax.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-pass
+// compile-flags: --error-format=human
+
+/// ```
+/// \__________pkt->size___________/ \_result->size_/ \__pkt->size__/
+/// ```
+pub fn foo() {}

src/test/rustdoc-ui/invalid-syntax.stderr

@@ -0,0 +1,10 @@
+Output from rustc:
+error: unknown start of token: /
+ --> <stdin>:1:1
+ |
+1 | /__________pkt->size___________/ /_result->size_/ /__pkt->size__/
+ | ^
+
+warning: Invalid doc comment starting with: `/__________pkt->size___________/ /_result->size_/ /__pkt->size__/`
+(Ignoring this codeblock)
+