Fixes the issue that an update removes the custom ID field on the node (resolves #95) (#96)

Author: Andy2003

src/main/kotlin/org/neo4j/graphql/handler/MergeOrUpdateHandler.kt

@@ -31,7 +31,7 @@ class MergeOrUpdateHandler private constructor(
         }
 
         override fun createDataFetcher(rootType: GraphQLObjectType, fieldDefinition: GraphQLFieldDefinition): DataFetcher<Cypher>? {
-            if (rootType.name != MUTATION){
+            if (rootType.name != MUTATION) {
                 return null
             }
             if (fieldDefinition.cypherDirective() != null) {
@@ -67,8 +67,13 @@ class MergeOrUpdateHandler private constructor(
     }
 
     init {
-        defaultFields.clear()
-        propertyFields.remove(idField.name) // id should not be updated
+        defaultFields.clear() // for marge or updates we do not reset to defaults
+        if (idField.isNativeId() || merge) {
+            // native id cannot be updated
+            // if the ID is not a native ID and we are in the update mode, we do not remove it from the properties
+            // b/c otherwise the id field will be unset
+            propertyFields.remove(idField.name)
+        }
     }
 
     override fun generateCypher(variable: String, field: Field, env: DataFetchingEnvironment): Cypher {

src/test/resources/dynamic-property-tests.adoc

@@ -105,6 +105,7 @@ mutation {
 ----
 MATCH (updatePerson:Person { id: $updatePersonId })
 SET updatePerson = {
+  id: $updatePersonId,
   `properties.foo`: $updatePersonJsonFoo,
   `properties.x`: $updatePersonJsonX
 }
@@ -245,4 +246,4 @@ SET mergeKnows += { `prefix.foo`: $mergeKnowsJsonFoo }
 WITH mergeKnows RETURN mergeKnows {
   json:apoc.map.fromPairs([key IN keys(mergeKnows) WHERE key STARTS WITH 'prefix.'| [substring(key,7), mergeKnows[key]]])
 } AS mergeKnows
-----
+----