Detect ending front matter delimiter at EOF

src/strings.rs

@@ -299,11 +299,16 @@ pub fn split_off_front_matter<'s>(mut s: &'s str, delimiter: &str) -> Option<(&'
     start += match s[start..]
         .find(&("\n".to_string() + delimiter + "\r\n"))
         .or_else(|| s[start..].find(&("\n".to_string() + delimiter + "\n")))
+        .or_else(|| s[start..].find(&("\n".to_string() + delimiter))) // delimiter followed by EOF
     {
         Some(n) => n + 1 + delimiter.len(),
         None => return None,
     };
 
+    if start == s.len() {
+        return Some((s, ""));
+    }
+
     start += if s[start..].starts_with('\n') {
         1
     } else if s[start..].starts_with("\r\n") {

src/tests/front_matter.rs

@@ -179,3 +179,37 @@ fn second_line() {
 
     assert!(found.is_none(), "no FrontMatter expected");
 }
+
+#[test]
+fn fm_only_with_trailing_newline() {
+    let input = "---\nfoo: bar\n---\n";
+
+    let mut options = Options::default();
+    options.extension.front_matter_delimiter = Some("---".to_owned());
+    let arena = Arena::new();
+    let root = parse_document(&arena, input, &options);
+
+    let found = root
+        .descendants()
+        .filter(|n| matches!(n.data.borrow().value, NodeValue::FrontMatter(..)))
+        .next();
+
+    assert!(found.is_some(), "front matter expected");
+}
+
+#[test]
+fn fm_only_without_trailing_newline() {
+    let input = "---\nfoo: bar\n---";
+
+    let mut options = Options::default();
+    options.extension.front_matter_delimiter = Some("---".to_owned());
+    let arena = Arena::new();
+    let root = parse_document(&arena, input, &options);
+
+    let found = root
+        .descendants()
+        .filter(|n| matches!(n.data.borrow().value, NodeValue::FrontMatter(..)))
+        .next();
+
+    assert!(found.is_some(), "front matter expected");
+}