Fix infinite loop on {....

parser/src/scanner.rs

@@ -2177,7 +2177,7 @@ impl<T: Input> Scanner<T> {
         loop {
             self.input.lookahead(4);
             if self.input.next_is_document_end()
-                || (self.input.next_is_document_start() && self.leading_whitespace)
+                || (self.leading_whitespace && self.input.next_is_document_start())
                 || self.input.peek() == '#'
             {
                 break;
@@ -2293,10 +2293,20 @@ impl<T: Input> Scanner<T> {
             self.allow_simple_key();
         }
 
-        Ok(Token(
-            Span::new(start_mark, end_mark),
-            TokenType::Scalar(TScalarStyle::Plain, string),
-        ))
+        if string.is_empty() {
+            // `fetch_plain_scalar` must absolutely consume at least one byte. Otherwise,
+            // `fetch_next_token` will never stop calling it. An empty plain scalar may happen with
+            // erroneous inputs such as "{...".
+            Err(ScanError::new_str(
+                start_mark,
+                "unexpected end of plain scalar",
+            ))
+        } else {
+            Ok(Token(
+                Span::new(start_mark, end_mark),
+                TokenType::Scalar(TScalarStyle::Plain, string),
+            ))
+        }
     }
 
     fn fetch_key(&mut self) -> ScanResult {

parser/tests/issues.rs

@@ -214,6 +214,17 @@ fn test_issue14() {
     );
 }
 
+#[test]
+fn test_issue14_v2() {
+    let s = "{...";
+    let Err(error) = run_parser(s) else { panic!() };
+    assert_eq!(error.info(), "unexpected end of plain scalar");
+    assert_eq!(
+        error.to_string(),
+        "unexpected end of plain scalar at byte 1 line 1 column 2"
+    );
+}
+
 #[test]
 fn test_issue13() {
     // The following input creates an infinite loop.

parser/tests/yaml-test-suite.rs

@@ -94,7 +94,8 @@ fn load_tests_from_file(entry: &DirEntry) -> Result<Vec<Test<YamlTest>>> {
     let test_name = file_name
         .strip_suffix(".yaml")
         .ok_or("unexpected filename")?;
-    let tests = Yaml::load_from_str(&fs::read_to_string(entry.path())?)?;
+    let tests = Yaml::load_from_str(&fs::read_to_string(entry.path())?)
+        .map_err(|e| format!("While reading {file_name}: {e}"))?;
     let tests = tests[0].as_vec().ok_or("no test list found in file")?;
 
     let mut result = vec![];