propogate errors

boa/src/builtins/json/mod.rs

@@ -99,14 +99,13 @@ pub fn stringify(_: &mut Value, args: &[Value], interpreter: &mut Interpreter) -
                         key.to_owned(),
                         Property::default().value(
                             interpreter
-                                .call(replacer, &mut this_arg, &[Value::string(key), val.clone()])
-                                .expect("failed to get returned value from replacer function"),
+                                .call(replacer, &mut this_arg, &[Value::string(key), val.clone()])?,
                         ),
                     );
                 }
-                Value::from(object_to_return.to_json().to_string())
+                Ok(Value::from(object_to_return.to_json().to_string()))
             })
-            .ok_or_else(Value::undefined)
+            .ok_or_else(Value::undefined)?
     } else if replacer_as_object.kind == ObjectKind::Array {
         let mut obj_to_return =
             serde_json::Map::with_capacity(replacer_as_object.properties.len() - 1);

boa/src/builtins/json/tests.rs

@@ -153,3 +153,15 @@ fn json_stringify_array_converts_symbol_to_null() {
 
     assert_eq!(actual, expected);
 }
+ #[test]
+ fn json_stringify_function_replacer_propogate_error() {
+     let realm = Realm::create();
+     let mut engine = Interpreter::new(realm);
+
+     let actual = forward(&mut engine, r#"JSON.stringify({x: 1}, (key, value) => {
+         throw new TypeError("type error")
+     })"#);
+     let expected = forward(&mut engine, r#"'Error: undefined'"#);
+
+     assert_eq!(actual, expected);
+ }