add note

src/connector/src/with_options_test.rs

@@ -48,6 +48,13 @@ pub fn generate_with_options_yaml_sink() -> String {
 
 /// Collect all structs with `#[derive(WithOptions)]` in the `.rs` files in `path` (plus `common.rs`),
 /// and generate a YAML file.
+///
+/// Note: here we assumes the struct is parsed by `serde`. If it's not the case,
+/// the generated `yaml` might be inconsistent with the actual parsing logic.
+/// TODO: improve the test to check whether serde is used.
+///
+/// - For sources, the parsing logic is in `TryFromHashMap`.
+/// - For sinks, the parsing logic is in `TryFrom<SinkParam>`.
 fn generate_with_options_yaml_inner(path: &Path) -> String {
     let mut structs = vec![];
     let mut functions = BTreeMap::<String, FunctionInfo>::new();
@@ -278,6 +285,9 @@ fn extract_serde_properties(field: &Field) -> SerdeProperties {
 ///     // ...
 /// }
 /// ```
+///
+/// Note: here we assumes `#[serde(flatten)]` is used for struct fields. If it's not the case,
+/// the generated `yaml` might be inconsistent with the actual parsing logic.
 fn flatten_nested_options(options: BTreeMap<String, StructInfo>) -> BTreeMap<String, StructInfo> {
     let mut deleted_keys = HashSet::new();