Fix ExprCollectionValue serialization bug

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/data/model/ExprCollectionValue.java

@@ -18,11 +18,10 @@
 import com.amazon.opendistroforelasticsearch.sql.data.type.ExprCoreType;
 import com.amazon.opendistroforelasticsearch.sql.data.type.ExprType;
 import com.google.common.base.Objects;
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
 import java.util.stream.Collectors;
-import lombok.EqualsAndHashCode;
 import lombok.RequiredArgsConstructor;
 
 /**
@@ -34,7 +33,11 @@ public class ExprCollectionValue extends AbstractExprValue {
 
   @Override
   public Object value() {
-    return valueList;
+    List<Object> results = new ArrayList<>();
+    for (ExprValue exprValue : valueList) {
+      results.add(exprValue.value());
+    }
+    return results;
   }
 
   @Override

protocol/src/test/java/com/amazon/opendistroforelasticsearch/sql/protocol/response/format/SimpleJsonResponseFormatterTest.java

@@ -129,6 +129,25 @@ void formatResponseWithTupleValue() {
         formatter.format(response));
   }
 
+  @Test
+  void formatResponseWithArrayValue() {
+    QueryResult response =
+        new QueryResult(
+            schema,
+            Arrays.asList(
+                tupleValue(ImmutableMap
+                    .of("name", "Smith",
+                        "address", Arrays.asList(
+                            ImmutableMap.of("state", "WA"), ImmutableMap.of("state", "NYC")
+                        )))));
+    SimpleJsonResponseFormatter formatter = new SimpleJsonResponseFormatter(COMPACT);
+    assertEquals(
+        "{\"schema\":[{\"name\":\"firstname\",\"type\":\"string\"},"
+            + "{\"name\":\"age\",\"type\":\"integer\"}],"
+            + "\"datarows\":[[\"Smith\",[{\"state\":\"WA\"},{\"state\":\"NYC\"}]]],"
+            + "\"total\":1,\"size\":1}",
+        formatter.format(response));
+  }
 
   @Test
   void formatError() {