Add support for GraphQL Scalar ID (#54)

Author: gscheibel

src/main/kotlin/com/expedia/graphql/annotations/GraphQLID.kt

@@ -0,0 +1,6 @@
+package com.expedia.graphql.annotations
+
+/**
+ * Used to indicate that a property of type Int, String, Long, java.util.UUID is a GraphqQL Scalar ID
+ */
+annotation class GraphQLID

src/main/kotlin/com/expedia/graphql/schema/extensions/annotationExtensions.kt

@@ -1,6 +1,7 @@
 package com.expedia.graphql.schema.extensions
 
 import com.expedia.graphql.annotations.GraphQLDescription
+import com.expedia.graphql.annotations.GraphQLID
 import com.expedia.graphql.annotations.GraphQLIgnore
 import com.expedia.graphql.schema.exceptions.CouldNotGetNameOfAnnotationException
 import com.expedia.graphql.schema.generator.isNotBlackListed
@@ -60,6 +61,8 @@ internal fun KAnnotatedElement.getDeprecationReason(): String? {
 
 internal fun KAnnotatedElement.isGraphQLIgnored() = this.findAnnotation<GraphQLIgnore>() != null
 
+internal fun KAnnotatedElement.isGraphQLID() = this.findAnnotation<GraphQLID>() != null
+
 internal fun Annotation.getDirectiveInfo() =
     this.annotationClass.annotations.find { it is DirectiveAnnotation } as? DirectiveAnnotation
 

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

@@ -13,6 +13,7 @@ import com.expedia.graphql.schema.extensions.getValidFunctions
 import com.expedia.graphql.schema.extensions.getValidProperties
 import com.expedia.graphql.schema.extensions.graphQLDescription
 import com.expedia.graphql.schema.extensions.isGraphQLContext
+import com.expedia.graphql.schema.extensions.isGraphQLID
 import com.expedia.graphql.schema.extensions.throwIfUnathorizedInterface
 import com.expedia.graphql.schema.extensions.wrapInNonNull
 import com.expedia.graphql.schema.generator.types.defaultGraphQLScalars
@@ -156,7 +157,7 @@ internal class SchemaGenerator(
     }
 
     private fun property(prop: KProperty<*>): GraphQLFieldDefinition {
-        val propertyType = graphQLTypeOf(prop.returnType) as GraphQLOutputType
+        val propertyType = graphQLTypeOf(type = prop.returnType, annotatedAsID = prop.isGraphQLID()) as GraphQLOutputType
 
         val fieldBuilder = GraphQLFieldDefinition.newFieldDefinition()
                 .description(prop.graphQLDescription())
@@ -180,9 +181,9 @@ internal class SchemaGenerator(
             .build()
     }
 
-    private fun graphQLTypeOf(type: KType, inputType: Boolean = false): GraphQLType {
+    private fun graphQLTypeOf(type: KType, inputType: Boolean = false, annotatedAsID: Boolean = false): GraphQLType {
         val hookGraphQLType = config.hooks.willGenerateGraphQLType(type)
-        val graphQLType = hookGraphQLType ?: defaultGraphQLScalars(type) ?: objectFromReflection(type, inputType)
+        val graphQLType = hookGraphQLType ?: defaultGraphQLScalars(type, annotatedAsID) ?: objectFromReflection(type, inputType)
         val typeWithNullityTakenIntoAccount = graphQLType.wrapInNonNull(type)
         config.hooks.didGenerateGraphQLType(type, typeWithNullityTakenIntoAccount)
         return typeWithNullityTakenIntoAccount

src/main/kotlin/com/expedia/graphql/schema/generator/types/defaultGraphQLScalars.kt

@@ -4,6 +4,7 @@ import graphql.Scalars
 import graphql.schema.GraphQLType
 import java.math.BigDecimal
 import java.math.BigInteger
+import java.util.UUID
 import kotlin.reflect.KClass
 import kotlin.reflect.KType
 
@@ -20,8 +21,18 @@ private val defaultScalarsMap = mapOf(
     Boolean::class to Scalars.GraphQLBoolean
 )
 
-internal fun defaultGraphQLScalars(type: KType): GraphQLType? {
-    val kclass = type.classifier as? KClass<*>
+private val validIdTypes = listOf(Int::class, String::class, Long::class, UUID::class)
 
-    return defaultScalarsMap[kclass]
+internal fun defaultGraphQLScalars(type: KType, annotatedAsID: Boolean = false): GraphQLType? {
+    val kclass = type.classifier as? KClass<*>
+    return if (annotatedAsID) {
+        if (validIdTypes.contains(kclass)) {
+            Scalars.GraphQLID
+        } else {
+            val types = validIdTypes.joinToString(prefix = "[", postfix = "]", separator = ", ") { it.qualifiedName ?: "" }
+            throw IllegalArgumentException("${kclass?.simpleName} is not a valid ID type, only $types are accepted")
+        }
+    } else {
+        defaultScalarsMap[kclass]
+    }
 }

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

@@ -2,23 +2,26 @@ package com.expedia.graphql.schema.generator
 
 import com.expedia.graphql.TopLevelObjectDef
 import com.expedia.graphql.annotations.GraphQLDescription
+import com.expedia.graphql.annotations.GraphQLID
 import com.expedia.graphql.annotations.GraphQLIgnore
 import com.expedia.graphql.schema.exceptions.ConflictingTypesException
 import com.expedia.graphql.schema.exceptions.InvalidSchemaException
 import com.expedia.graphql.schema.extensions.deepName
 import com.expedia.graphql.schema.testSchemaConfig
 import com.expedia.graphql.toSchema
 import graphql.GraphQL
+import graphql.schema.GraphQLNonNull
 import graphql.schema.GraphQLObjectType
 import org.junit.jupiter.api.Assertions.assertNull
 import org.junit.jupiter.api.Assertions.assertThrows
 import java.net.CookieManager
+import java.util.UUID
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
-@Suppress("Detekt.UnusedPrivateMember", "Detekt.FunctionOnlyReturningConstant")
+@Suppress("Detekt.UnusedPrivateMember", "Detekt.FunctionOnlyReturningConstant", "Detekt.LargeClass")
 class SchemaGeneratorTest {
     @Test
     fun `SchemaGenerator generates a simple GraphQL schema`() {
@@ -228,6 +231,26 @@ class SchemaGeneratorTest {
         assertNull(firstChild?.get("children"))
     }
 
+    @Test
+    fun `SchemaGenerator support GraphQLID scalar`() {
+        val schema = toSchema(queries = listOf(TopLevelObjectDef(QueryWithId())), config = testSchemaConfig)
+
+        val placeType = schema.getObjectType("PlaceOfIds")
+        assertEquals(graphql.Scalars.GraphQLID, (placeType.getFieldDefinition("intId").type as? GraphQLNonNull)?.wrappedType)
+        assertEquals(graphql.Scalars.GraphQLID, (placeType.getFieldDefinition("longId").type as? GraphQLNonNull)?.wrappedType)
+        assertEquals(graphql.Scalars.GraphQLID, (placeType.getFieldDefinition("stringId").type as? GraphQLNonNull)?.wrappedType)
+        assertEquals(graphql.Scalars.GraphQLID, (placeType.getFieldDefinition("uuid").type as? GraphQLNonNull)?.wrappedType)
+    }
+
+    @Test
+    fun `SchemaGenerator throws an exception for invalid GraphQLID`() {
+        val exception = assertThrows(IllegalArgumentException::class.java) {
+            toSchema(queries = listOf(TopLevelObjectDef(QueryWithInvalidId())), config = testSchemaConfig)
+        }
+
+        assertEquals("Person is not a valid ID type, only [kotlin.Int, kotlin.String, kotlin.Long, java.util.UUID] are accepted", exception.message)
+    }
+
     class QueryObject {
         @GraphQLDescription("A GraphQL query method")
         fun query(@GraphQLDescription("A GraphQL value") value: Int): Geography = Geography(value, GeoType.CITY, listOf())
@@ -355,4 +378,21 @@ class SchemaGeneratorTest {
     }
 
     data class Person(val name: String, val children: List<Person>? = null)
+
+    data class PlaceOfIds(
+        @property:GraphQLID val intId: Int,
+        @property:GraphQLID val longId: Long,
+        @property:GraphQLID val stringId: String,
+        @property:GraphQLID val uuid: UUID
+    )
+
+    data class InvalidIds(@property:GraphQLID val person: Person)
+
+    class QueryWithId {
+        fun query(): PlaceOfIds = PlaceOfIds(42, 24, "42", UUID.randomUUID())
+    }
+
+    class QueryWithInvalidId {
+        fun query(): InvalidIds = InvalidIds(Person("person id not a valid type id"))
+    }
 }