Prevent type from being recreated when mixing interfaces and unions (#62)

Author: gscheibel

src/main/kotlin/com/expedia/graphql/schema/generator/SchemaGenerator.kt

@@ -271,7 +271,7 @@ internal class SchemaGenerator(
     }
 
     private fun interfaceType(kClass: KClass<*>): GraphQLType {
-        return state.cache.buildIfNotUnderConstruction(kClass) { _ ->
+        return state.cache.buildIfNotUnderConstruction(kClass) {
             val builder = GraphQLInterfaceType.newInterface()
 
             builder.name(kClass.simpleName)
@@ -293,16 +293,19 @@ internal class SchemaGenerator(
                         val objectType = objectType(it.kotlin, interfaceType)
                         val key = TypesCacheKey(it.kotlin.createType(), false)
 
-                        state.additionalTypes.add(objectType)
                         state.cache.put(key, KGraphQLType(it.kotlin, objectType))
+                        if (objectType !is GraphQLTypeReference) {
+                            state.additionalTypes.add(objectType)
+                        }
+                        state.cache.removeTypeUnderConstruction(it.kotlin)
                     }
 
             interfaceType
         }
     }
 
     private fun unionType(kClass: KClass<*>): GraphQLType {
-        return state.cache.buildIfNotUnderConstruction(kClass) { _ ->
+        return state.cache.buildIfNotUnderConstruction(kClass) {
             val builder = GraphQLUnionType.newUnionType()
 
             builder.name(kClass.simpleName)
@@ -313,7 +316,8 @@ internal class SchemaGenerator(
             implementations
                     .filterNot { it.kotlin.isAbstract }
                     .forEach {
-                        val objectType = objectType(it.kotlin)
+                        val objectType = state.cache.get(TypesCacheKey(it.kotlin.createType(), false)) ?: objectType(it.kotlin)
+
                         val key = TypesCacheKey(it.kotlin.createType(), false)
 
                         if (objectType is GraphQLTypeReference) {
@@ -323,6 +327,9 @@ internal class SchemaGenerator(
                         }
 
                         state.cache.put(key, KGraphQLType(it.kotlin, objectType))
+                        if (state.cache.doesNotContain(it.kotlin)) {
+                            state.cache.put(key, KGraphQLType(it.kotlin, objectType))
+                        }
                     }
 
             builder.build()

src/main/kotlin/com/expedia/graphql/schema/generator/TypesCache.kt

@@ -44,6 +44,8 @@ internal class TypesCache(private val supportedPackages: List<String>) {
     fun doesNotContainGraphQLType(graphQLType: GraphQLType) =
         cache.none { (_, v) -> v.graphQLType.name == graphQLType.name }
 
+    fun doesNotContain(kClass: KClass<*>): Boolean = cache.none { (_, ktype) -> ktype.kClass == kClass }
+
     @Throws(CouldNotGetNameOfEnumException::class)
     private fun getCacheKeyString(cacheKey: TypesCacheKey): String {
         val kClass = getKClassFromKType(cacheKey.type)
@@ -91,6 +93,8 @@ internal class TypesCache(private val supportedPackages: List<String>) {
 
     private fun putTypeUnderConstruction(kClass: KClass<*>) = typeUnderConstruction.add(kClass)
 
+    fun removeTypeUnderConstruction(kClass: KClass<*>) = typeUnderConstruction.remove(kClass)
+
     fun buildIfNotUnderConstruction(kClass: KClass<*>, build: (KClass<*>) -> GraphQLType): GraphQLType {
         return if (typeUnderConstruction.contains(kClass)) {
             GraphQLTypeReference.typeRef(kClass.simpleName)

src/test/kotlin/com/expedia/graphql/schema/generator/PolymorphicTests.kt

@@ -89,6 +89,7 @@ class PolymorphicTests {
 }
 
 class QueryWithInterface {
+    fun fromUnion(): Union = AnImplementation()
     fun query(): AnInterface = AnImplementation()
     fun fromImplementation(): AnImplementation = AnImplementation()
 }
@@ -101,14 +102,16 @@ class QueryWithUnAuthorizedUnionArgument {
     fun notAllowed(body: BodyPart): BodyPart = body
 }
 
+interface Union
+
 interface AnInterface {
     val property: String
 }
 
 data class AnImplementation(
     override val property: String = "A value",
     val implementationSpecific: String = "It's implementation specific"
-) : AnInterface
+) : AnInterface, Union
 
 class QueryWithUnion {
     fun query(whichHand: String): BodyPart = when (whichHand) {