fix(style): ensure nested style variables are processed during formatting (#5120)

fix: ensure nested style variables are processed during formatting

src/formatter/model.rs

@@ -91,6 +91,7 @@ impl<'a> StyleVariableHolder<Cow<'a, str>> for Vec<FormatElement<'a>> {
         self.iter().fold(BTreeSet::new(), |mut acc, el| match el {
             FormatElement::TextGroup(textgroup) => {
                 acc.extend(textgroup.style.get_style_variables());
+                acc.extend(textgroup.format.get_style_variables());
                 acc
             }
             FormatElement::Conditional(format) => {

src/formatter/string_formatter.rs

@@ -569,6 +569,30 @@ mod tests {
         match_next!(result_iter, "inner", inner_style);
     }
 
+    #[test]
+    fn test_style_variable_nested() {
+        const STYLE_VAR_NAME: &str = "style";
+
+        let format_string = format!("[[text](${STYLE_VAR_NAME})](blue)");
+        let inner_style = Some(Color::Red.bold());
+
+        let formatter = StringFormatter::new(&format_string)
+            .unwrap()
+            .map_style(|variable| match variable {
+                STYLE_VAR_NAME => Some(Ok("red bold".to_owned())),
+                _ => None,
+            });
+
+        assert_eq!(
+            BTreeSet::from([STYLE_VAR_NAME.into()]),
+            formatter.get_style_variables()
+        );
+
+        let result = formatter.parse(None, None).unwrap();
+        let mut result_iter = result.iter();
+        match_next!(result_iter, "text", inner_style);
+    }
+
     #[test]
     fn test_styled_variable_as_text() {
         const FORMAT_STR: &str = "[$var](red bold)";