fix

Signed-off-by: luofucong <luofc@foxmail.com>

src/datatypes/src/json/value.rs

@@ -160,6 +160,16 @@ impl JsonVariant {
         }
     }
 
+    fn contains_empty_object(&self) -> bool {
+        match self {
+            JsonVariant::Array(array) => array.iter().any(JsonVariant::contains_empty_object),
+            JsonVariant::Object(object) => {
+                object.is_empty() || object.values().any(JsonVariant::contains_empty_object)
+            }
+            _ => false,
+        }
+    }
+
     fn as_ref(&self) -> JsonVariantRef<'_> {
         match self {
             JsonVariant::Null => JsonVariantRef::Null,
@@ -433,7 +443,7 @@ impl JsonValue {
     /// Returns an error if the value cannot be aligned without losing existing object fields or
     /// when a scalar type conversion is incompatible.
     pub(crate) fn try_align(&mut self, expected: &JsonNativeType) -> Result<()> {
-        if is_include(expected, self.json_type()) {
+        if is_include(expected, self.json_type()) && !self.json_variant.contains_empty_object() {
             return Ok(());
         }
 
@@ -896,6 +906,23 @@ mod tests {
             ])))
         );
 
+        // Empty objects have native type Null, but the value still needs alignment
+        // before converting into a typed struct value.
+        let expected = JsonNativeType::Object(JsonObjectType::from([(
+            "empty".to_string(),
+            JsonNativeType::Null,
+        )]));
+        let mut value = parse_json_value(r#"{"empty":{}}"#);
+        assert_eq!(value.json_type(), &expected);
+        value.try_align(&expected)?;
+        assert_eq!(
+            value,
+            JsonValue::from(JsonVariant::Object(BTreeMap::from([(
+                "empty".to_string(),
+                JsonVariant::Null,
+            )])))
+        );
+
         // Object alignment should fail if the expected type misses any field from the value.
         let expected = JsonNativeType::Object(JsonObjectType::from([(
             "items".to_string(),