Added ability to return lists of DataFetcherResults in functions (#1150)

Author: teoboley

generator/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/internal/types/utils/functionReturnTypes.kt

@@ -22,6 +22,9 @@ import graphql.execution.DataFetcherResult
 import org.reactivestreams.Publisher
 import java.util.concurrent.CompletableFuture
 import kotlin.reflect.KType
+import kotlin.reflect.KTypeProjection
+import kotlin.reflect.KVariance
+import kotlin.reflect.full.createType
 
 /**
  * These are the classes that can be returned from data fetchers (ie functions)
@@ -38,12 +41,16 @@ import kotlin.reflect.KType
  *      Publisher<DataFetcherResult<T>>
  *      CompletableFuture<T>
  *      CompletableFuture<DataFetcherResult<T>>
+ *      List<DataFetcherResult<T>>
  */
 internal fun getWrappedReturnType(returnType: KType): KType {
     return when {
         returnType.isSubclassOf(DataFetcherResult::class) -> returnType.getTypeOfFirstArgument()
         returnType.isSubclassOf(Publisher::class) -> { checkTypeForDataFetcherResult(returnType) }
         returnType.isSubclassOf(CompletableFuture::class) -> { checkTypeForDataFetcherResult(returnType) }
+        returnType.isSubclassOf(List::class) && returnType.getTypeOfFirstArgument().isSubclassOf(DataFetcherResult::class) -> {
+            List::class.createType(listOf(KTypeProjection(KVariance.INVARIANT, getWrappedReturnType(returnType.getTypeOfFirstArgument()))))
+        }
         else -> returnType
     }
 }
@@ -55,6 +62,7 @@ internal fun getWrappedReturnType(returnType: KType): KType {
  *      Published<DataFetcherResult<T>>
  *      CompletableFuture<T>
  *      CompletableFuture<DataFetcherResult<T>>
+ *      List<DataFetcherResult<T>>
  */
 private fun checkTypeForDataFetcherResult(returnType: KType): KType {
     val wrappedType = returnType.getTypeOfFirstArgument()

generator/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/internal/types/utils/FunctionReturnTypesKtTest.kt

@@ -28,7 +28,9 @@ class FunctionReturnTypesKtTest {
     class MyClass {
         // Valid Types
         val string = "my string"
+        val listOfString: List<String> = listOf(string)
         val dataFetcherResult: DataFetcherResult<String> = DataFetcherResult.newResult<String>().data(string).build()
+        val listDataFetcherResult: List<DataFetcherResult<String>> = listOf(DataFetcherResult.newResult<String>().data(string).build())
         val publisher: Publisher<String> = Flowable.just(string)
         val flowable: Flowable<String> = Flowable.just(string)
         val publisherDataFetcherResult: Publisher<DataFetcherResult<String>> = Flowable.just(dataFetcherResult)
@@ -54,6 +56,11 @@ class FunctionReturnTypesKtTest {
         assertEquals(MyClass::publisher.returnType, actual = getWrappedReturnType(MyClass::invalidDataFetcherResultPublisher.returnType))
     }
 
+    @Test
+    fun `getWrappedReturnType of List of DataFetcherResult`() {
+        assertEquals(MyClass::listOfString.returnType, actual = getWrappedReturnType(MyClass::listDataFetcherResult.returnType))
+    }
+
     @Test
     fun `getWrappedReturnType of CompletableFuture`() {
         assertEquals(MyClass::string.returnType, actual = getWrappedReturnType(MyClass::completableFuture.returnType))

generator/graphql-kotlin-schema-generator/src/test/kotlin/com/expediagroup/graphql/generator/test/integration/DataFetcherResultListTest.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2021 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.test.integration
+
+import com.expediagroup.graphql.generator.TopLevelObject
+import com.expediagroup.graphql.generator.testSchemaConfig
+import com.expediagroup.graphql.generator.toSchema
+import graphql.execution.DataFetcherResult
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+
+class DataFetcherResultListTest {
+
+    @Test
+    fun validateSchema() {
+        val queries = listOf(TopLevelObject(SimpleQuery()))
+        val schema = toSchema(testSchemaConfig, queries)
+        assertNotNull(schema)
+        assertEquals("String!", schema.queryType.getFieldDefinition("getString").type.toString())
+        assertEquals("String!", schema.queryType.getFieldDefinition("getDataFetcherResultString").type.toString())
+        assertEquals("[String!]!", schema.queryType.getFieldDefinition("getListString").type.toString())
+    }
+
+    class SimpleQuery {
+        private val string = "hello"
+
+        fun getString(): String = string
+        fun getDataFetcherResultString(): DataFetcherResult<String> =
+            DataFetcherResult.newResult<String>().data(string).build()
+        fun getListString(): List<DataFetcherResult<String>> = listOf(DataFetcherResult.newResult<String>().data(string).build())
+    }
+}