feat: new hook for modifying object types (#232)

Fixes #231

Adds a new hook that can be used to modify all the GraphQLTypes that get generated from reflection. This allows for runtime documentation or any other changes that may want to be made to types after they are fully generated

Author: Shane Myrick

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

@@ -23,9 +23,12 @@ internal open class TypeBuilder constructor(protected val generator: SchemaGener
         val graphQLType = hookGraphQLType
             ?: generator.scalarType(type, annotatedAsID)
             ?: objectFromReflection(type, inputType)
-        val typeWithNullityTakenIntoAccount = graphQLType.wrapInNonNull(type)
-        config.hooks.didGenerateGraphQLType(type, typeWithNullityTakenIntoAccount)
-        return typeWithNullityTakenIntoAccount
+
+        val typeWithNullability = graphQLType.wrapInNonNull(type)
+
+        config.hooks.didGenerateGraphQLType(type, typeWithNullability)
+
+        return typeWithNullability
     }
 
     internal fun objectFromReflection(type: KType, inputType: Boolean): GraphQLType {
@@ -39,12 +42,14 @@ internal open class TypeBuilder constructor(protected val generator: SchemaGener
         val kClass = type.getKClass()
         val graphQLType = getGraphQLType(kClass, inputType, type)
 
-        if (graphQLType !is GraphQLTypeReference) {
-            val kGraphQLType = KGraphQLType(kClass, graphQLType)
+        val modifiedGraphQLType = config.hooks.willAddGraphQLTypeToSchema(type, graphQLType)
+
+        if (modifiedGraphQLType !is GraphQLTypeReference) {
+            val kGraphQLType = KGraphQLType(kClass, modifiedGraphQLType)
             state.cache.put(cacheKey, kGraphQLType)
         }
 
-        return graphQLType
+        return modifiedGraphQLType
     }
 
     private fun getGraphQLType(kClass: KClass<*>, inputType: Boolean, type: KType): GraphQLType = when {

src/main/kotlin/com/expedia/graphql/hooks/SchemaGeneratorHooks.kt

@@ -28,6 +28,12 @@ interface SchemaGeneratorHooks {
     @Suppress("Detekt.FunctionOnlyReturningConstant")
     fun willGenerateGraphQLType(type: KType): GraphQLType? = null
 
+    /**
+     * Called after using reflection to generate the graphql object type but before returning it to the schema builder.
+     * This allows for modifying the type info, like description or directives
+     */
+    fun willAddGraphQLTypeToSchema(type: KType, generatedType: GraphQLType): GraphQLType = generatedType
+
     /**
      * Called before resolving a KType to the GraphQL type.
      * This allows for a custom resolver on how to extract wrapped values, like in a CompletableFuture.

src/test/kotlin/com/expedia/graphql/hooks/SchemaGeneratorHooksTest.kt

@@ -123,6 +123,32 @@ class SchemaGeneratorHooksTest {
         assertEquals("SomeData!", hooks.lastSeenGeneratedType?.deepName)
     }
 
+    @Test
+    fun `calls hook before adding type to schema`() {
+        class MockSchemaGeneratorHooks : SchemaGeneratorHooks {
+            var hookCalled = false
+
+            override fun willAddGraphQLTypeToSchema(type: KType, generatedType: GraphQLType): GraphQLType {
+                hookCalled = true
+                return when {
+                    generatedType is GraphQLObjectType && generatedType.name == "SomeData" -> GraphQLObjectType.Builder(generatedType).description("My custom description").build()
+                    else -> generatedType
+                }
+            }
+        }
+
+        val hooks = MockSchemaGeneratorHooks()
+        val schema = toSchema(
+            queries = listOf(TopLevelObject(TestQuery())),
+            config = getTestSchemaConfigWithHooks(hooks)
+        )
+        assertTrue(hooks.hookCalled)
+
+        val type = schema.getObjectType("SomeData")
+        assertNotNull(type)
+        assertEquals(expected = "My custom description", actual = type.description)
+    }
+
     @Test
     fun `calls hook before adding query to schema`() {
         class MockSchemaGeneratorHooks : SchemaGeneratorHooks {