fix(6.x.x): return result of getter resolved at runtime (#2104)

Co-authored-by: Samuel Vazquez <samvazquez@expediagroup.com>

Author: samuelAndalon

generator/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/execution/SingletonPropertyDataFetcher.kt

@@ -1,3 +1,19 @@
+/*
+ * Copyright 2025 Expedia, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package com.expediagroup.graphql.generator.execution
 
 import graphql.schema.DataFetcher
@@ -31,27 +47,23 @@ internal object SingletonPropertyDataFetcher : LightDataFetcher<Any?> {
         fieldDefinition: GraphQLFieldDefinition,
         sourceObject: Any?,
         environmentSupplier: Supplier<DataFetchingEnvironment>
-    ): Any? =
-        sourceObject?.let {
-            val getter = getters["${sourceObject.javaClass.name}.${fieldDefinition.name}"]
-            when {
-                getter != null -> getter.call(sourceObject)
-                else -> {
-                    sourceObject::class.memberProperties
-                        .find { it.name == fieldDefinition.name }
-                        ?.let { kProperty ->
-                            kProperty.getter.call(sourceObject).also {
-                                register(sourceObject::class, kProperty)
-                            }
-                        }
-                }
+    ): Any? {
+        if (sourceObject == null) return null
+
+        val getter = getters["${sourceObject.javaClass.name}.${fieldDefinition.name}"]
+        if (getter != null) return getter.call(sourceObject)
+
+        return sourceObject::class.memberProperties
+            .find { it.name == fieldDefinition.name }
+            ?.let { kProperty ->
+                register(sourceObject::class, kProperty)
+                return kProperty.getter.call(sourceObject)
             } ?: run {
-                logger.error("getter method not found: ${sourceObject.javaClass.name}.${fieldDefinition.name}")
-            }
+            logger.error("getter method not found: ${sourceObject.javaClass.name}.${fieldDefinition.name}")
+            return null
         }
+    }
 
     override fun get(environment: DataFetchingEnvironment): Any? =
-        environment.getSource<Any?>()?.let { sourceObject ->
-            getters["${sourceObject.javaClass.name}.${environment.fieldDefinition.name}"]?.call(sourceObject)
-        }
+        get(environment.fieldDefinition, environment.getSource()) { environment }
 }