Remove the dependency on object instances so the schema can be generated as a standalone without datafetchers (#198)

Author: gscheibel

src/main/kotlin/com/expedia/graphql/TopLevelObject.kt

@@ -9,4 +9,7 @@ import kotlin.reflect.KClass
  * @param obj The target object (or proxy to target object)
  * @param kClass Optional KClass of the target (or the proxied object)
  */
-data class TopLevelObject(val obj: Any, val kClass: KClass<*> = obj::class)
+data class TopLevelObject(val obj: Any?, val kClass: KClass<*>) {
+    constructor(obj: Any) : this(obj, obj::class)
+    constructor(kClass: KClass<*>) : this(null, kClass)
+}

src/main/kotlin/com/expedia/graphql/generator/SubTypeMapper.kt

@@ -7,7 +7,5 @@ internal class SubTypeMapper(supportedPackages: List<String>) {
 
     private val reflections = Reflections(supportedPackages)
 
-    fun getSubTypesOf(kclass: KClass<*>): List<Class<*>> =
-        reflections.getSubTypesOf(Class.forName(kclass.javaObjectType.name))
-            .filterNot { it.kotlin.isAbstract }
+    fun getSubTypesOf(kclass: KClass<*>): List<Class<*>> = reflections.getSubTypesOf(kclass.java).filterNot { it.kotlin.isAbstract }
 }

src/test/kotlin/com/expedia/graphql/ToSchemaKtTest.kt

@@ -1,14 +1,27 @@
 package com.expedia.graphql
 
 import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
 
 class ToSchemaKtTest {
 
-    class TestClass
+    @Suppress("FunctionOnlyReturningConstant")
+    class TestClass {
+        fun greeting() = "Hello World"
+    }
 
     @Test
     fun `valid schema`() {
         val queries = listOf(TopLevelObject(TestClass()))
         toSchema(queries = queries, config = testSchemaConfig)
     }
+
+    @Test
+    fun `generate standalone SDL`() {
+        val queries = listOf(TopLevelObject(TestClass::class))
+        val schema = toSchema(queries = queries, config = testSchemaConfig)
+
+        val greetingField = schema.queryType.getFieldDefinition("greeting")
+        assertEquals("String!", greetingField.type.toString())
+    }
 }