fix: loop given empty string

promkit/src/grapheme.rs

@@ -164,6 +164,10 @@ impl StyledGraphemes {
 
     pub fn highlight<S: AsRef<str>>(mut self, query: S, style: ContentStyle) -> Option<Self> {
         let query_str = query.as_ref();
+        if query_str.is_empty() {
+            return None;
+        }
+
         let mut result = VecDeque::new();
 
         let mut current_index = 0;
@@ -186,7 +190,7 @@ impl StyledGraphemes {
             // Apply style to all matching graphemes
             while current_index < match_end {
                 let mut grapheme = self.0[current_index].clone();
-                grapheme.apply_style(style.clone());
+                grapheme.apply_style(style);
                 result.push_back(grapheme);
                 current_index += 1;
             }
@@ -387,6 +391,18 @@ mod test {
 
         use super::*;
 
+        #[test]
+        fn test_apply_style_to_empty_query() {
+            let graphemes = StyledGraphemes::from("Hello, world!");
+            let new_style = StyleBuilder::new().fgc(Color::Red).build();
+            let result = graphemes.highlight("", new_style);
+
+            assert!(
+                result.is_none(),
+                "Should return None for an empty query string"
+            );
+        }
+
         #[test]
         fn test_apply_style_to_repeated_substring() {
             let graphemes = StyledGraphemes::from("Hello, world! Hello, universe!");