fix: use enum value in GraphQLEnumValueDefinition (#2112)

### 📝 Description
Attempting to output an enum value with a custom `@GraphQLName`
annotation will currently result in something like:
> SerializationError{path=[enumOutputs, 3],
exception=graphql.schema.CoercingSerializeException: Invalid input for
enum 'MyTestEnum'. Unknown value 'FOUR'}

This PR changes the GraphQLEnumValueDefinition `value` to be the enum
entry itself rather than the graphql name, which allows graphql-java to
correctly resolve the name from the definition.

### 🔗 Related Issues

Author: tKe

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

@@ -56,7 +56,7 @@ private fun getEnumValueDefinition(generator: SchemaGenerator, enum: Enum<*>, kC
     validateGraphQLEnumValue(name, kClass)
 
     valueBuilder.name(name)
-    valueBuilder.value(name)
+    valueBuilder.value(enum)
 
     generateEnumValueDirectives(generator, valueField, kClass.getSimpleName()).forEach {
         valueBuilder.withAppliedDirective(it)

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

@@ -68,10 +68,14 @@ class GenerateEnumTest : TypeTestHelper() {
         val actual = generateEnum(generator, MyTestEnum::class)
         assertEquals(expected = 4, actual = actual.values.size)
         assertEquals(expected = "MyTestEnum", actual = actual.name)
-        assertEquals(expected = "ONE", actual = actual.values[0].value)
-        assertEquals(expected = "TWO", actual = actual.values[1].value)
-        assertEquals(expected = "THREE", actual = actual.values[2].value)
-        assertEquals(expected = "customFour", actual = actual.values[3].value)
+        assertEquals(expected = "ONE", actual = actual.values[0].name)
+        assertEquals(expected = MyTestEnum.ONE, actual = actual.values[0].value)
+        assertEquals(expected = "TWO", actual = actual.values[1].name)
+        assertEquals(expected = MyTestEnum.TWO, actual = actual.values[1].value)
+        assertEquals(expected = "THREE", actual = actual.values[2].name)
+        assertEquals(expected = MyTestEnum.THREE, actual = actual.values[2].value)
+        assertEquals(expected = "customFour", actual = actual.values[3].name)
+        assertEquals(expected = MyTestEnum.FOUR, actual = actual.values[3].value)
     }
 
     @Test

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

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2020 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.internal.types.GenerateEnumTest
+import com.expediagroup.graphql.generator.testSchemaConfig
+import com.expediagroup.graphql.generator.toSchema
+import graphql.GraphQL
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+@Suppress(
+    "Detekt.UnusedPrivateMember",
+)
+class CustomEnumExecutionTest {
+
+    private val schema = toSchema(
+        queries = listOf(TopLevelObject(QueryObject())),
+        config = testSchemaConfig()
+    )
+    private val graphQL: GraphQL = GraphQL.newGraphQL(schema).build()
+
+    @Test
+    fun `a custom enum name can be used as output`() {
+        val result = graphQL.execute("{ enumOutputs }")
+        val data: Map<String, List<String>>? = result.getData()
+
+        assertEquals(emptyList(), result.errors)
+        assertEquals(listOf("ONE", "TWO", "THREE", "customFour"), data?.get("enumOutputs"))
+    }
+
+    @Test
+    fun `an implicit enum name be used as input`() {
+        val result = graphQL.execute("{ enumInput(value: THREE) }")
+        val data: Map<String, String>? = result.getData()
+
+        assertEquals(emptyList(), result.errors)
+        assertEquals("hello, THREE", data?.get("enumInput"))
+    }
+
+    @Test
+    fun `a custom enum name be used as input`() {
+        val result = graphQL.execute("{ enumInput(value: customFour) }")
+        val data: Map<String, String>? = result.getData()
+
+        assertEquals(emptyList(), result.errors)
+        assertEquals("hello, FOUR", data?.get("enumInput"))
+    }
+
+    class QueryObject {
+        fun enumOutputs(): List<GenerateEnumTest.MyTestEnum> = GenerateEnumTest.MyTestEnum.entries
+        fun enumInput(value: GenerateEnumTest.MyTestEnum) = "hello, $value"
+    }
+}