fix(cut): reject malformed rectangle cut bounds

crates/engine/src/cmd/cut.rs

@@ -221,9 +221,11 @@ fn rect_cut(s: &mut Session, p: &Value) -> Result<Value> {
     const C: &str = "path.rectCut";
     let rect = match p.get("rect") {
         Some(v) => {
-            let a: Vec<f64> = v.as_array().map(|a| a.iter().filter_map(Value::as_f64).collect()).unwrap_or_default();
-            let [x, y, w, h] = a[..] else { return Err(bad(C, "rect must be [x, y, width, height]")) };
-            Rect::new(x, y, x + w, y + h).abs()
+            // Every component must be present and numeric. Dropping invalid elements would
+            // silently cut the wrong region when a malformed five-element array is supplied.
+            let values = v.as_array().filter(|a| a.len() == 4).and_then(|a| a.iter().map(Value::as_f64).collect::<Option<Vec<_>>>());
+            let Some([x, y, w, h]) = values.as_deref() else { return Err(bad(C, "rect must be [x, y, width, height]")) };
+            Rect::new(*x, *y, x + w, y + h).abs()
         }
         None => Rect::from_points(point_req(p, "from", C)?, point_req(p, "to", C)?),
     };

crates/engine/src/tests_cut.rs

@@ -118,6 +118,29 @@ fn line_cut_that_misses_changes_nothing() {
     assert!(s.execute("path.lineCut", &json!({"from": [5, 5]})).is_err());
 }
 
+
+#[test]
+fn rect_cut_rejects_non_numeric_rectangle_elements_without_modifying_art() {
+    let mut s = session();
+    let id = rect(&mut s, 0.0, 0.0, 100.0, 100.0);
+    select(&mut s, &[id]);
+    let original = bounds(&s, id);
+    let history = undo_depth(&s);
+    // The old parser dropped the string and used the four remaining values.
+    for params in [
+        json!([0, "ignored", 10, 50, 50]),
+        json!([0, 10, 50, null, 50]),
+        json!([0, 10, 50, 50, 5]),
+    ] {
+        assert!(s.execute("path.rectCut", &json!({"rect": params})).is_err());
+        assert!(near(bounds(&s, id), original), "failed cut must not change geometry");
+        assert_eq!(undo_depth(&s), history, "failed cut must not add undo history");
+    }
+    // Proper rectangular cuts still work.
+    s.execute("path.rectCut", &json!({"rect": [10, 10, 70, 70]})).unwrap();
+    assert!(near(bounds(&s, id), Rect::new(10.0, 10.0, 80.0, 80.0)));
+}
+
 #[test]
 fn rect_cut_crops_to_real_geometry() {
     let mut s = session();