fix: most error spans mistakenly being empty

With codespan_reporting an empty span shows up exactly like a
one-byte span, which is why I didn't notice this mistake earlier.

4 files changed, 17 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 259447b..8579e4d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -36,6 +36,8 @@
 
 * Fixed attribute value spans being wrong for values containing character references.
 
+* Fixed most error spans mistakenly being empty.
+
 * Fixed some error spans being off-by-one  
   (`eof-*`).
 
diff --git a/src/emitter.rs b/src/emitter.rs
index a014025..d28b11b 100644
--- a/src/emitter.rs
+++ b/src/emitter.rs
@@ -339,7 +339,7 @@ impl<O: Offset> Emitter<O> for DefaultEmitter<O> {
                 *self_closing = true;
             }
             Token::EndTag(_) => {
-                self.emit_error(Error::EndTagWithTrailingSolidus, offset - 1..offset - 1);
+                self.emit_error(Error::EndTagWithTrailingSolidus, offset - 1..offset);
             }
             _ => {
                 debug_assert!(false);
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 6cf930f..871074e 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -185,7 +185,7 @@ impl<R: Reader + Position<O>, O: Offset, E: Emitter<O>> Tokenizer<R, O, E> {
             | Error::EofInDoctype
             | Error::EofInScriptHtmlCommentLikeText
             | Error::EofInTag => self.reader.position()..self.reader.position(),
-            _ => self.reader.position() - 1..self.reader.position() - 1,
+            _ => self.reader.position() - 1..self.reader.position(),
         };
         self.emitter.emit_error(error, span);
     }
diff --git a/tests/test_spans.rs b/tests/test_spans.rs
index e839f53..28342ea 100644
--- a/tests/test_spans.rs
+++ b/tests/test_spans.rs
@@ -213,9 +213,20 @@ fn doctype_id_spans() {
 fn annotate_errors(html: &'static str) -> String {
     let mut labels = Vec::new();
     for token in tokenizer(html) {
-        if let Token::Error { error, span } = token {
-            labels.push((span, error.code()));
+        let Token::Error { error, span } = token else {
+            continue;
+        };
+
+        if span.start == span.end {
+            if span.start != html.len() {
+                panic!("empty error spans are only allowed at the very end of the source (for eof errors)");
+            }
+        } else {
+            assert!(span.start < span.end);
+            assert!(span.end <= html.len());
         }
+
+        labels.push((span, error.code()));
     }
     annotate(html, labels)
 }