Examples for method and argument based custom directives. (#73)

* Examples for method and argument based custom directives.

* Refactoring, code shenanigans

* Kotlin to v1.3.10 to fix a reflection issue.
(Library kotlin dependency was raised for the name reason)

* Refactoring

Author: d4rken

example/pom.xml

@@ -60,7 +60,7 @@
 
     <properties>
         <java.version>1.8</java.version>
-        <kotlin.version>1.2.71</kotlin.version>
+        <kotlin.version>1.3.10</kotlin.version>
         <junit.version>4.12</junit.version>
         <graphiql.version>5.0.2</graphiql.version>
         <graphql-kotlin.version>0.0.24</graphql-kotlin.version>

example/src/main/kotlin/com.expedia.graphql.sample/Application.kt

@@ -3,6 +3,7 @@ package com.expedia.graphql.sample
 import com.expedia.graphql.TopLevelObjectDef
 import com.expedia.graphql.sample.context.MyGraphQLContextBuilder
 import com.expedia.graphql.sample.dataFetchers.SpringDataFetcherFactory
+import com.expedia.graphql.sample.directives.DirectiveWiringFactory
 import com.expedia.graphql.sample.exceptions.CustomDataFetcherExceptionHandler
 import com.expedia.graphql.sample.extension.CustomSchemaGeneratorHooks
 import com.expedia.graphql.sample.mutation.Mutation
@@ -36,9 +37,12 @@ class Application {
     private val logger = LoggerFactory.getLogger(Application::class.java)
 
     @Bean
-    fun schemaConfig(dataFetcherFactory: SpringDataFetcherFactory, validator: Validator): SchemaGeneratorConfig = SchemaGeneratorConfig(
+    fun wiringFactory() = DirectiveWiringFactory()
+
+    @Bean
+    fun schemaConfig(dataFetcherFactory: SpringDataFetcherFactory, validator: Validator, wiringFactory: DirectiveWiringFactory): SchemaGeneratorConfig = SchemaGeneratorConfig(
             supportedPackages = listOf("com.expedia"),
-            hooks = CustomSchemaGeneratorHooks(validator),
+            hooks = CustomSchemaGeneratorHooks(validator, wiringFactory),
             dataFetcherFactory = dataFetcherFactory
     )
 
@@ -85,7 +89,7 @@ class Application {
     @Bean
     fun graphQLObjectMapper(): GraphQLObjectMapper = GraphQLObjectMapper.newBuilder()
             .withObjectMapperConfigurer(ObjectMapperConfigurer { it.registerModule(KotlinModule()) })
-            .withGraphQLErrorHandler( GraphQLErrorHandler { it })
+            .withGraphQLErrorHandler(GraphQLErrorHandler { it })
             .build()
 
     @Bean

example/src/main/kotlin/com.expedia.graphql.sample/directives/CakeOnly.kt

@@ -0,0 +1,6 @@
+package com.expedia.graphql.sample.directives
+
+import com.expedia.graphql.annotations.GraphQLDirective
+
+@GraphQLDirective(description = "This validates string input")
+annotation class CakeOnly

example/src/main/kotlin/com.expedia.graphql.sample/directives/CakeOnlyDirectiveWiring.kt

@@ -0,0 +1,25 @@
+package com.expedia.graphql.sample.directives
+
+import graphql.schema.DataFetcher
+import graphql.schema.GraphQLFieldDefinition
+import graphql.schema.idl.SchemaDirectiveWiringEnvironment
+
+class CakeOnlyDirectiveWiring : DirectiveWiring {
+
+    override fun isApplicable(environment: SchemaDirectiveWiringEnvironment<*>): Boolean =
+            environment.directive.name == getDirectiveName(CakeOnly::class)
+
+
+    override fun onField(wiringEnv: SchemaDirectiveWiringEnvironment<GraphQLFieldDefinition>): GraphQLFieldDefinition {
+        val field = wiringEnv.element
+        val originalDataFetcher: DataFetcher<Any> = field.dataFetcher
+        val cakeOnlyFetcher = DataFetcher<Any> { dataEnv ->
+            val strArg: String? = dataEnv.getArgument(wiringEnv.element.arguments[0].name) as String?
+            if (strArg != "Cake") {
+                throw RuntimeException("The cake is a lie!")
+            }
+            originalDataFetcher.get(dataEnv)
+        }
+        return field.transform { it.dataFetcher(cakeOnlyFetcher) }
+    }
+}

example/src/main/kotlin/com.expedia.graphql.sample/directives/DirectiveWiring.kt

@@ -0,0 +1,15 @@
+package com.expedia.graphql.sample.directives
+
+import com.google.common.base.CaseFormat
+import graphql.schema.idl.SchemaDirectiveWiring
+import graphql.schema.idl.SchemaDirectiveWiringEnvironment
+import kotlin.reflect.KClass
+
+interface DirectiveWiring : SchemaDirectiveWiring {
+
+    fun isApplicable(environment: SchemaDirectiveWiringEnvironment<*>): Boolean
+
+}
+
+fun getDirectiveName(kClass: KClass<out Annotation>): String =
+        CaseFormat.UPPER_CAMEL.to(CaseFormat.LOWER_CAMEL, kClass.simpleName!!)

example/src/main/kotlin/com.expedia.graphql.sample/directives/DirectiveWiringFactory.kt

@@ -0,0 +1,20 @@
+package com.expedia.graphql.sample.directives
+
+import graphql.schema.idl.SchemaDirectiveWiring
+import graphql.schema.idl.SchemaDirectiveWiringEnvironment
+import graphql.schema.idl.WiringFactory
+
+class DirectiveWiringFactory : WiringFactory {
+    private val wiring = listOf(
+            StringEvalDirectiveWiring(),
+            CakeOnlyDirectiveWiring()
+    )
+
+    override fun providesSchemaDirectiveWiring(environment: SchemaDirectiveWiringEnvironment<*>): Boolean = true
+
+    override fun getSchemaDirectiveWiring(environment: SchemaDirectiveWiringEnvironment<*>): SchemaDirectiveWiring? =
+            wiring.asSequence()
+                    .filter { it.isApplicable(environment) }
+                    .singleOrNull()
+
+}

example/src/main/kotlin/com.expedia.graphql.sample/directives/StringEval.kt

@@ -0,0 +1,9 @@
+package com.expedia.graphql.sample.directives
+
+import com.expedia.graphql.annotations.GraphQLDirective
+
+@GraphQLDirective(description = "This validates string input")
+annotation class StringEval(
+        val default: String = "",
+        val lowerCase: Boolean = false
+)

example/src/main/kotlin/com.expedia.graphql.sample/directives/StringEvalDirectiveWiring.kt

@@ -0,0 +1,41 @@
+package com.expedia.graphql.sample.directives
+
+import graphql.schema.DataFetcher
+import graphql.schema.DataFetchingEnvironmentBuilder
+import graphql.schema.GraphQLFieldDefinition
+import graphql.schema.idl.SchemaDirectiveWiringEnvironment
+
+class StringEvalDirectiveWiring : DirectiveWiring {
+    private val dirName = getDirectiveName(StringEval::class)
+
+    override fun isApplicable(environment: SchemaDirectiveWiringEnvironment<*>): Boolean =
+            (environment.element as? GraphQLFieldDefinition)?.arguments?.any { it.getDirective(dirName) != null }
+                    ?: false
+
+    override fun onField(wiringEnv: SchemaDirectiveWiringEnvironment<GraphQLFieldDefinition>): GraphQLFieldDefinition {
+        val field = wiringEnv.element
+        val originalDataFetcher: DataFetcher<Any> = field.dataFetcher
+
+        val defaultValueFetcher = DataFetcher<Any> { dataEnv ->
+            val newArguments = HashMap(dataEnv.arguments)
+            wiringEnv.element.arguments.asSequence()
+                    .map { gqlArg ->
+                        val strArg: String? = dataEnv.getArgument(gqlArg.name) as String?
+                        Pair(gqlArg, strArg)
+                    }
+                    .forEach { (gqlArg, value) ->
+                        if (gqlArg.getDirective(dirName).getArgument(StringEval::lowerCase.name).value as Boolean) {
+                            newArguments[gqlArg.name] = value?.toLowerCase()
+                        }
+                        if (value.isNullOrEmpty()) {
+                            newArguments[gqlArg.name] = gqlArg.getDirective(dirName).getArgument(StringEval::default.name).value as String
+                        }
+                    }
+            val newEnv = DataFetchingEnvironmentBuilder.newDataFetchingEnvironment(dataEnv)
+                    .arguments(newArguments)
+                    .build()
+            originalDataFetcher.get(newEnv)
+        }
+        return field.transform { it.dataFetcher(defaultValueFetcher) }
+    }
+}

example/src/main/kotlin/com.expedia.graphql.sample/extension/CustomSchemaGeneratorHooks.kt

@@ -1,22 +1,24 @@
 package com.expedia.graphql.sample.extension
 
+import com.expedia.graphql.sample.directives.DirectiveWiringFactory
 import com.expedia.graphql.sample.validation.DataFetcherExecutionValidator
+import com.expedia.graphql.schema.generator.directive.DirectiveWiringHelper
 import com.expedia.graphql.schema.hooks.DataFetcherExecutionPredicate
 import com.expedia.graphql.schema.hooks.SchemaGeneratorHooks
 import graphql.language.StringValue
 import graphql.schema.Coercing
 import graphql.schema.GraphQLScalarType
 import graphql.schema.GraphQLType
-import java.util.UUID
+import java.util.*
 import javax.validation.Validator
 import kotlin.reflect.KClass
 import kotlin.reflect.KType
 
 /**
  * Schema generator hook that adds additional scalar types.
  */
-class CustomSchemaGeneratorHooks(validator: Validator) : SchemaGeneratorHooks {
-
+class CustomSchemaGeneratorHooks(validator: Validator, wiringFactory: DirectiveWiringFactory) : SchemaGeneratorHooks {
+    private val directiveWiringHelper = DirectiveWiringHelper(wiringFactory)
     /**
      * Register additional GraphQL scalar types.
      */
@@ -25,6 +27,10 @@ class CustomSchemaGeneratorHooks(validator: Validator) : SchemaGeneratorHooks {
         else -> null
     }
 
+    override fun onRewireGraphQLType(type: KType, generatedType: GraphQLType): GraphQLType {
+        return directiveWiringHelper.onWire(generatedType)
+    }
+
     override val dataFetcherExecutionPredicate: DataFetcherExecutionPredicate? = DataFetcherExecutionValidator(validator)
 }
 

example/src/main/kotlin/com.expedia.graphql.sample/query/CustomDirectiveQuery.kt

@@ -0,0 +1,17 @@
+package com.expedia.graphql.sample.query
+
+import com.expedia.graphql.annotations.GraphQLDescription
+import com.expedia.graphql.sample.directives.CakeOnly
+import com.expedia.graphql.sample.directives.StringEval
+import org.springframework.stereotype.Component
+
+@Component
+class CustomDirectiveQuery : Query {
+
+    @GraphQLDescription("Returns a message modified by directives, lower case and non-empty")
+    fun justWhisper(@StringEval(default = "Default String", lowerCase = true) msg: String): String = msg
+
+    @GraphQLDescription("This will only accept 'Cake' as input")
+    @CakeOnly
+    fun onlyCake(msg: String): String = "<3"
+}