buffer lexer errors in rustdoc syntax checking

src/librustdoc/passes/check_code_block_syntax.rs

@@ -1,6 +1,7 @@
-use errors::Applicability;
+use errors::{emitter::Emitter, Applicability, Diagnostic, Handler};
+use rustc_data_structures::sync::{Lock, Lrc};
 use rustc_parse::lexer::StringReader as Lexer;
-use rustc_span::source_map::FilePathMapping;
+use rustc_span::source_map::{FilePathMapping, SourceMap};
 use rustc_span::{FileName, InnerSpan};
 use syntax::sess::ParseSess;
 use syntax::token;
@@ -27,7 +28,13 @@ struct SyntaxChecker<'a, 'tcx> {
 
 impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
     fn check_rust_syntax(&self, item: &clean::Item, dox: &str, code_block: RustCodeBlock) {
-        let sess = ParseSess::new(FilePathMapping::empty());
+        let buffered_messages = Lrc::new(Lock::new(vec![]));
+
+        let emitter = BufferEmitter { messages: Lrc::clone(&buffered_messages) };
+
+        let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let handler = Handler::with_emitter(false, None, Box::new(emitter));
+        let sess = ParseSess::with_span_handler(handler, cm);
         let source_file = sess.source_map().new_source_file(
             FileName::Custom(String::from("doctest")),
             dox[code_block.code].to_owned(),
@@ -93,6 +100,11 @@ impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
                 diag
             };
 
+            // FIXME(#67563): Provide more context for these errors by displaying the spans inline.
+            for message in buffered_messages.borrow().iter() {
+                diag.note(&message);
+            }
+
             diag.emit();
         }
     }
@@ -110,6 +122,20 @@ impl<'a, 'tcx> DocFolder for SyntaxChecker<'a, 'tcx> {
     }
 }
 
+struct BufferEmitter {
+    messages: Lrc<Lock<Vec<String>>>,
+}
+
+impl Emitter for BufferEmitter {
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        self.messages.borrow_mut().push(format!("error from rustc: {}", diag.message[0].0));
+    }
+
+    fn source_map(&self) -> Option<&Lrc<SourceMap>> {
+        None
+    }
+}
+
 enum CodeBlockInvalid {
     SyntaxError,
     Empty,

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

@@ -1,21 +1,3 @@
-error: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | \__________pkt->size___________/          \_result->size_/ \__pkt->size__/
-  | ^
-
-error: unknown start of token: \
- --> <doctest>:1:43
-  |
-1 | \__________pkt->size___________/          \_result->size_/ \__pkt->size__/
-  |                                           ^
-
-error: unknown start of token: \
- --> <doctest>:1:60
-  |
-1 | \__________pkt->size___________/          \_result->size_/ \__pkt->size__/
-  |                                                            ^
-
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:3:5
    |
@@ -25,33 +7,14 @@ LL | | /// \__________pkt->size___________/          \_result->size_/ \__pkt->si
 LL | | /// ```
    | |_______^
    |
+   = note: error from rustc: unknown start of token: \
+   = note: error from rustc: unknown start of token: \
+   = note: error from rustc: unknown start of token: \
 help: mark blocks that do not contain Rust code as text
    |
 LL | /// ```text
    |     ^^^^^^^
 
-error: unknown start of token: `
- --> <doctest>:3:30
-  |
-3 |    |     ^^^^^^ did you mean `baz::foobar`?
-  |                              ^
-  |
-help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
-  |
-3 |    |     ^^^^^^ did you mean 'baz::foobar`?
-  |                              ^
-
-error: unknown start of token: `
- --> <doctest>:3:42
-  |
-3 |    |     ^^^^^^ did you mean `baz::foobar`?
-  |                                          ^
-  |
-help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
-  |
-3 |    |     ^^^^^^ did you mean `baz::foobar'?
-  |                                          ^
-
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:9:5
    |
@@ -63,17 +26,13 @@ LL | | ///    |     ^^^^^^ did you mean `baz::foobar`?
 LL | | /// ```
    | |_______^
    |
+   = note: error from rustc: unknown start of token: `
+   = note: error from rustc: unknown start of token: `
 help: mark blocks that do not contain Rust code as text
    |
 LL | /// ```text
    |     ^^^^^^^
 
-error: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | \_
-  | ^
-
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:21:5
    |
@@ -83,17 +42,12 @@ LL | | /// \_
 LL | | /// ```
    | |_______^
    |
+   = note: error from rustc: unknown start of token: \
 help: mark blocks that do not contain Rust code as text
    |
 LL | /// ```text
    |     ^^^^^^^
 
-error: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | \_
-  | ^
-
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:35:5
    |
@@ -102,12 +56,8 @@ LL |   /// ```rust
 LL | | /// \_
 LL | | /// ```
    | |_______^
-
+   |
-error: unknown start of token: \
+   = note: error from rustc: unknown start of token: \
- --> <doctest>:2:5
-  |
-2 |     \_
-  |     ^
 
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:45:9
@@ -116,51 +66,18 @@ LL |   ///     code with bad syntax
    |  _________^
 LL | | ///     \_
    | |__________^
-
+   |
-error: unknown start of token: `
+   = note: error from rustc: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | ```
-  | ^
-  |
-help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
-  |
-1 | '``
-  | ^
-
-error: unknown start of token: `
- --> <doctest>:1:2
-  |
-1 | ```
-  |  ^
-  |
-help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
-  |
-1 | `'`
-  |  ^
-
-error: unknown start of token: `
- --> <doctest>:1:3
-  |
-1 | ```
-  |   ^
-  |
-help: Unicode character '`' (Grave Accent) looks like ''' (Single Quote), but it is not
-  |
-1 | ``'
-  |   ^
 
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:60:9
    |
 LL | ///     ```
    |         ^^^
-
+   |
-error: unknown start of token: \
+   = note: error from rustc: unknown start of token: `
- --> <doctest>:1:1
+   = note: error from rustc: unknown start of token: `
-  |
+   = note: error from rustc: unknown start of token: `
-1 | \_
-  | ^
 
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:64:5
@@ -170,12 +87,8 @@ LL |   /// ```edition2018
 LL | | /// \_
 LL | | /// ```
    | |_______^
-
+   |
-error: unknown start of token: \
+   = note: error from rustc: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | \_
-  | ^
 
 warning: doc comment contains an invalid Rust code block
   --> $DIR/invalid-syntax.rs:70:1
@@ -186,6 +99,7 @@ LL | | #[doc = "```"]
    | |______________^
    |
    = help: mark blocks that do not contain Rust code as text: ```text
+   = note: error from rustc: unknown start of token: \
 
 warning: Rust code block is empty
   --> $DIR/invalid-syntax.rs:76:5
@@ -210,15 +124,11 @@ help: mark blocks that do not contain Rust code as text
 LL | /// ```text
    |     ^^^^^^^
 
-error: unknown start of token: \
- --> <doctest>:1:1
-  |
-1 | \____/
-  | ^
-
 warning: could not parse code block as Rust code
   --> $DIR/invalid-syntax.rs:92:9
    |
 LL | ///     \____/
    |         ^^^^^^
+   |
+   = note: error from rustc: unknown start of token: \