Handle empty object setting via createOrReplace method (#176)

* Handle empty object setting via createOrReplace method

Author: suresh-prakash

document-store/src/integrationTest/resources/create/document_one.json

@@ -8,7 +8,8 @@
     {
       "name": "Mars",
       "color": "Red",
-      "humans_live": "possibly in future"
+      "humans_live": "possibly in future",
+      "tags": {}
     }
   ]
 }

document-store/src/integrationTest/resources/create/document_one_response.json

@@ -9,7 +9,8 @@
       {
         "name": "Mars",
         "color": "Red",
-        "humans_live": "possibly in future"
+        "humans_live": "possibly in future",
+        "tags": {}
       }
     ]
   }

document-store/src/integrationTest/resources/create/document_two.json

@@ -2,5 +2,6 @@
   "planet_name": "Mars",
   "planet_color": "Red",
   "humans_live": true,
-  "settlement_since": 2099
+  "settlement_since": 2099,
+  "tags": {}
 }

document-store/src/integrationTest/resources/create/document_two_response.json

@@ -3,6 +3,7 @@
     "planet_name": "Mars",
     "planet_color": "Red",
     "humans_live": true,
-    "settlement_since": 2099
+    "settlement_since": 2099,
+    "tags": {}
   }
 ]

document-store/src/main/java/org/hypertrace/core/documentstore/mongo/MongoCollection.java

@@ -432,11 +432,7 @@ public BulkUpdateResult bulkOperationOnArrayValue(BulkArrayValueUpdateRequest re
   private BasicDBObject getSubDocumentUpdateObject(
       final String subDocPath, final Document subDocument) {
     try {
-      /* Wrapping the subDocument with $literal to be able to provide empty object "{}" as value
-       *  Throws error otherwise if empty object is provided as value.
-       *  https://jira.mongodb.org/browse/SERVER-54046 */
-      BasicDBObject literalObject =
-          new BasicDBObject("$literal", getSanitizedBasicDBObject(subDocument));
+      BasicDBObject literalObject = getSanitizedBasicDBObject(subDocument);
       BasicDBObject dbObject = new BasicDBObject(subDocPath, literalObject);
       dbObject.append(LAST_UPDATED_TIME, System.currentTimeMillis());
       return new BasicDBObject("$set", dbObject);

document-store/src/main/java/org/hypertrace/core/documentstore/mongo/MongoUtils.java

@@ -24,7 +24,7 @@
 import java.util.Map.Entry;
 import java.util.Optional;
 import java.util.Set;
-import java.util.function.Function;
+import java.util.function.UnaryOperator;
 import org.bson.json.JsonMode;
 import org.bson.json.JsonWriterSettings;
 import org.hypertrace.core.documentstore.Document;
@@ -34,6 +34,7 @@
 public final class MongoUtils {
   public static final String FIELD_SEPARATOR = ".";
   public static final String PREFIX = "$";
+  private static final String LITERAL = PREFIX + "literal";
   private static final String UNSUPPORTED_OPERATION = "No MongoDB support available for: '%s'";
   private static final ObjectMapper MAPPER = new ObjectMapper();
   private static final Map<ReturnDocumentType, ReturnDocument> RETURN_DOCUMENT_MAP =
@@ -66,7 +67,8 @@ public static String decodeKey(final String key) {
   public static String sanitizeJsonString(final String jsonString) throws JsonProcessingException {
     final JsonNode jsonNode = MAPPER.readTree(jsonString);
     // escape "." and "$" in field names since Mongo DB does not like them
-    final JsonNode sanitizedJsonNode = recursiveClone(jsonNode, MongoUtils::encodeKey);
+    final JsonNode sanitizedJsonNode =
+        recursiveClone(jsonNode, MongoUtils::encodeKey, MongoUtils::wrapInLiteral);
     return MAPPER.writeValueAsString(sanitizedJsonNode);
   }
 
@@ -79,7 +81,10 @@ public static BasicDBObject merge(final List<BasicDBObject> basicDbObjects) {
                 toUnmodifiableMap(Entry::getKey, Entry::getValue), BasicDBObject::new));
   }
 
-  public static JsonNode recursiveClone(JsonNode src, Function<String, String> function) {
+  public static JsonNode recursiveClone(
+      JsonNode src,
+      UnaryOperator<String> function,
+      final UnaryOperator<ObjectNode> emptyObjectConverter) {
     if (!src.isObject()) {
       return src;
     }
@@ -92,11 +97,11 @@ public static JsonNode recursiveClone(JsonNode src, Function<String, String> fun
       JsonNode value = next.getValue();
       JsonNode newValue = value;
       if (value.isObject()) {
-        newValue = recursiveClone(value, function);
+        newValue = recursiveClone(value, function, emptyObjectConverter);
       }
       tgt.set(newFieldName, newValue);
     }
-    return tgt;
+    return tgt.isEmpty() ? emptyObjectConverter.apply(tgt) : tgt;
   }
 
   public static Document dbObjectToDocument(BasicDBObject dbObject) {
@@ -110,7 +115,8 @@ public static Document dbObjectToDocument(BasicDBObject dbObject) {
           JsonWriterSettings.builder().outputMode(JsonMode.RELAXED).build();
       jsonString = dbObject.toJson(relaxed);
       JsonNode jsonNode = MAPPER.readTree(jsonString);
-      JsonNode decodedJsonNode = recursiveClone(jsonNode, MongoUtils::decodeKey);
+      JsonNode decodedJsonNode =
+          recursiveClone(jsonNode, MongoUtils::decodeKey, UnaryOperator.identity());
       return new JSONDocument(decodedJsonNode);
     } catch (IOException e) {
       // throwing exception is not very useful here.
@@ -125,4 +131,13 @@ public static ReturnDocument getReturnDocument(final ReturnDocumentType returnDo
                 new UnsupportedOperationException(
                     String.format("Unhandled return document type: %s", returnDocumentType)));
   }
+
+  private static ObjectNode wrapInLiteral(final ObjectNode objectNode) {
+    /* Wrapping the subDocument with $literal to be able to provide empty object "{}" as value
+     *  Throws error otherwise if empty object is provided as value.
+     *  https://jira.mongodb.org/browse/SERVER-54046 */
+    final ObjectNode node = JsonNodeFactory.instance.objectNode();
+    node.set(LITERAL, objectNode);
+    return node;
+  }
 }