address review: empty-document range cannot overflow in set_attr

crates/keyframe/src/text_doc.rs

@@ -977,7 +977,8 @@ impl TextDoc {
             if r.start >= r.end && n > 0 {
                 return Ok(true);
             }
-            let range = r.start..r.end.max(r.start + usize::from(n == 0));
+            // Empty text: apply_style ignores the bounds, so a fixed range avoids `start + 1` overflow.
+            let range = if n == 0 { 0..1 } else { r.start..r.end };
             // Check every affected run first, so a value one run refuses changes none of them.
             let mut err = None;
             self.apply_style(range.clone(), |s| {
@@ -1377,6 +1378,12 @@ mod tests {
         assert_eq!(doc.style_at(0).variations.len(), MAX_VARIATION_AXES);
     }
 
+    #[test]
+    fn empty_document_accepts_an_extreme_range_without_overflow() {
+        let mut doc = TextDoc::plain("");
+        assert!(doc.set_attr("size", &J::from(20), Some(usize::MAX..usize::MAX)).unwrap());
+    }
+
     #[test]
     fn mixed_line_breaks_keep_original_byte_and_character_ranges() {
         let text = "é\r\nβ\rx\n\n";