fix(datastore): Flutter: fail to serialize list of custom type values

aws-datastore/src/main/java/com/amplifyframework/datastore/storage/sqlite/SQLiteModelFieldTypeConverter.java

@@ -45,7 +45,9 @@
 import java.time.OffsetTime;
 import java.time.ZoneOffset;
 import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
@@ -316,14 +318,26 @@ public Object convertValueFromTarget(Model model, ModelField field) throws DataS
             // We don't want to store entire SerializedCustomType along with schema into
             // Database but only its value.
             if (field.isCustomType() && fieldValue != null) {
-                fieldValue = ((SerializedCustomType) fieldValue).getFlatSerializedData();
+                if (field.isArray()) {
+                    @SuppressWarnings("unchecked")
+                    List<SerializedCustomType> listOfItems = (List<SerializedCustomType>) fieldValue;
+                    List<Map<String, Object>> listOfValues = new ArrayList<>();
+
+                    for (SerializedCustomType item : listOfItems) {
+                        listOfValues.add(item.getFlatSerializedData());
+                    }
+                    fieldValue = listOfValues;
+                } else {
+                    fieldValue = ((SerializedCustomType) fieldValue).getFlatSerializedData();
+                }
             }
         } else {
             fieldValue = ModelHelper.getValue(model, field);
         }
         if (fieldValue == null) {
             return null;
         }
+
         final JavaFieldType javaFieldType = TypeConverter.getJavaFieldType(field);
         return convertRawValueToTarget(fieldValue, javaFieldType, gson);
     }

aws-datastore/src/test/java/com/amplifyframework/datastore/storage/sqlite/SQLiteModelFieldTypeConverterTest.java

@@ -16,15 +16,26 @@
 package com.amplifyframework.datastore.storage.sqlite;
 
 import com.amplifyframework.AmplifyException;
+import com.amplifyframework.core.model.CustomTypeField;
+import com.amplifyframework.core.model.CustomTypeSchema;
+import com.amplifyframework.core.model.Model;
+import com.amplifyframework.core.model.ModelField;
+import com.amplifyframework.core.model.ModelSchema;
+import com.amplifyframework.core.model.SchemaRegistry;
+import com.amplifyframework.core.model.SerializedCustomType;
+import com.amplifyframework.core.model.SerializedModel;
 import com.amplifyframework.core.model.types.JavaFieldType;
+import com.amplifyframework.datastore.DataStoreException;
 import com.amplifyframework.util.GsonFactory;
 import com.amplifyframework.util.UserAgent;
 
 import com.google.gson.Gson;
 import org.junit.Before;
 import org.junit.Test;
 
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
@@ -100,4 +111,100 @@ public void testConvertRawValueToTargetDateTimeFlutter() throws AmplifyException
         final String expected = "2020-01-01T16:00:00.050020000";
         assertEquals(expected, actual);
     }
+
+    /**
+     * Test the convertValueFromTarget getting serialized value from a CustomType field in Flutter user cases.
+     * @throws DataStoreException Not expected.
+     */
+    @Test
+    public void testConvertFromCustomTypeTargetValueFlutter() throws DataStoreException {
+        SerializedModel model = getTestSerializedModel();
+        ModelField testField = ModelField.builder()
+                .name("customTypeField")
+                .javaClassForValue(Map.class)
+                .targetType("DummyCustomType")
+                .isRequired(true)
+                .isCustomType(true)
+                .build();
+
+        SQLiteModelFieldTypeConverter converter = new SQLiteModelFieldTypeConverter(
+                ModelSchema.builder().name("DummySchemaNotUsedInTest").modelType(Model.Type.USER).build(),
+                SchemaRegistry.instance(),
+                new Gson()
+        );
+
+        Object result = converter.convertValueFromTarget(model, testField);
+        assertEquals(result, "{\"phone\":\"4155555555\",\"countryCode\":\"+1\"}");
+    }
+
+    /**
+     * Test the convertValueFromTarget getting serialized value from a list of CustomType field in Flutter user cases.
+     * @throws DataStoreException Not expected.
+     */
+    @Test
+    public void testConvertFromListOfCustomTypeTargetValuesFlutter() throws DataStoreException {
+        SerializedModel model = getTestSerializedModel();
+        ModelField testField = ModelField.builder()
+                .name("listCustomTypeField")
+                .javaClassForValue(List.class)
+                .targetType("DummyCustomType")
+                .isRequired(true)
+                .isCustomType(true)
+                .isArray(true)
+                .build();
+
+        SQLiteModelFieldTypeConverter converter = new SQLiteModelFieldTypeConverter(
+                ModelSchema.builder().name("DummySchemaNotUsedInTest").modelType(Model.Type.USER).build(),
+                SchemaRegistry.instance(),
+                new Gson()
+        );
+
+        Object result = converter.convertValueFromTarget(model, testField);
+        assertEquals(result, "[{\"phone\":\"4155555555\",\"countryCode\":\"+1\"},{\"phone\":\"4155555555\"," +
+                "\"countryCode\":\"+1\"}]");
+    }
+
+    private SerializedModel getTestSerializedModel() {
+        Map<String, Object> serializedCustomTypeData = new HashMap<>();
+        serializedCustomTypeData.put("phone", "4155555555");
+        serializedCustomTypeData.put("countryCode", "+1");
+
+        Map<String, CustomTypeField> customTypeFields = new HashMap<>();
+        customTypeFields.put("phone", CustomTypeField.builder()
+                .name("phone")
+                .targetType("String")
+                .javaClassForValue(String.class)
+                .build());
+        customTypeFields.put("countryCode", CustomTypeField.builder()
+                .name("countryCode")
+                .targetType("String")
+                .javaClassForValue(String.class)
+                .build());
+
+        SerializedCustomType testCustomType = SerializedCustomType.builder()
+                .serializedData(serializedCustomTypeData)
+                .customTypeSchema(CustomTypeSchema.builder()
+                        .name("Phone")
+                        .pluralName("Phones")
+                        .fields(customTypeFields)
+                        .build())
+                .build();
+
+        List<SerializedCustomType> testCustomTypeList = new ArrayList<>();
+        testCustomTypeList.add(testCustomType);
+        testCustomTypeList.add(testCustomType);
+
+        Map<String, Object> serializedModelData = new HashMap<>();
+        serializedModelData.put("id", "dummy-id");
+        serializedModelData.put("customTypeField", testCustomType);
+        serializedModelData.put("listCustomTypeField", testCustomTypeList);
+
+        return SerializedModel.builder()
+                .modelSchema(ModelSchema.builder()
+                        .name("DummySchemaNotUsed")
+                        .modelClass(SerializedModel.class)
+                        .build())
+                .serializedData(serializedModelData)
+                .build();
+    }
 }