Reduce duplication in MethodFieldResolver.kt

Author: vojtapol

src/main/kotlin/graphql/kickstart/tools/resolver/FieldResolver.kt

@@ -35,7 +35,7 @@ internal abstract class FieldResolver(
         } else {
             SourceResolver { environment, sourceObject ->
                 val source = if (sourceObject != null) {
-                    // if source object is known environment is null as an optimization (LightDataFetcher)
+                    // if source object is known, environment is null as an optimization (LightDataFetcher)
                     sourceObject
                 } else {
                     environment

src/main/kotlin/graphql/kickstart/tools/resolver/MethodFieldResolver.kt

@@ -191,48 +191,33 @@ internal class MethodFieldResolver(
     override fun toString() = "MethodFieldResolver{method=$method}"
 }
 
-internal open class MethodFieldResolverDataFetcher(
+internal class MethodFieldResolverDataFetcher(
     private val sourceResolver: SourceResolver,
-    method: Method,
+    private val method: Method,
     private val args: List<ArgumentPlaceholder>,
     private val options: SchemaParserOptions,
 ) : DataFetcher<Any> {
 
-    private val resolverMethod = method
-    private val isSuspendFunction = try {
-        method.kotlinFunction?.isSuspend == true
-    } catch (e: InternalError) {
-        false
-    }
+    private val isSuspendFunction = method.isSuspendFunction()
 
     override fun get(environment: DataFetchingEnvironment): Any? {
         val source = sourceResolver.resolve(environment, null)
         val args = this.args.map { it(environment) }.toTypedArray()
 
         return if (isSuspendFunction) {
             environment.coroutineScope().future(options.coroutineContextProvider.provide()) {
-                invokeSuspend(source, resolverMethod, args)?.transformWithGenericWrapper(environment)
+                invokeSuspend(source, method, args)?.transformWithGenericWrapper(options.genericWrappers, { environment })
             }
         } else {
-            invoke(resolverMethod, source, args)?.transformWithGenericWrapper(environment)
+            invoke(method, source, args)?.transformWithGenericWrapper(options.genericWrappers, { environment })
         }
     }
 
-    private fun Any.transformWithGenericWrapper(environment: DataFetchingEnvironment): Any? {
-        return options.genericWrappers
-            .asSequence()
-            .filter { it.type.isInstance(this) }
-            .sortedWith(CompareGenericWrappers)
-            .firstOrNull()
-            ?.transformer?.invoke(this, environment) ?: this
-    }
-
     /**
-     * Function that returns the object used to fetch the data.
-     * It can be a DataFetcher or an entity.
+     * Function that returns the object used to fetch the data. It can be a DataFetcher or an entity.
      */
     @Suppress("unused")
-    open fun getWrappedFetchingObject(environment: DataFetchingEnvironment): Any {
+    fun getWrappedFetchingObject(environment: DataFetchingEnvironment): Any {
         return sourceResolver.resolve(environment, null)
     }
 }
@@ -247,38 +232,45 @@ internal class LightMethodFieldResolverDataFetcher(
     private val options: SchemaParserOptions,
 ) : LightDataFetcher<Any?> {
 
-    private val resolverMethod = method
-    private val isSuspendFunction = try {
-        method.kotlinFunction?.isSuspend == true
-    } catch (e: InternalError) {
-        false
-    }
+    private val isSuspendFunction = method.isSuspendFunction()
 
     override fun get(fieldDefinition: GraphQLFieldDefinition, sourceObject: Any, environmentSupplier: Supplier<DataFetchingEnvironment>): Any? {
         val source = sourceResolver.resolve(null, sourceObject)
+
         return if (isSuspendFunction) {
             environmentSupplier.get().coroutineScope().future(options.coroutineContextProvider.provide()) {
-                invokeSuspend(source, resolverMethod, emptyArray())?.transformWithGenericWrapper(environmentSupplier)
+                invokeSuspend(source, method, emptyArray())?.transformWithGenericWrapper(options.genericWrappers, environmentSupplier)
             }
         } else {
-            invoke(resolverMethod, source, emptyArray())?.transformWithGenericWrapper(environmentSupplier)
+            invoke(method, source, emptyArray())?.transformWithGenericWrapper(options.genericWrappers, environmentSupplier)
         }
     }
 
     override fun get(environment: DataFetchingEnvironment): Any? {
         return get(environment.fieldDefinition, sourceResolver.resolve(environment, null), { environment })
     }
 
-    private fun Any.transformWithGenericWrapper(environment: Supplier<DataFetchingEnvironment>): Any? {
-        return options.genericWrappers
-            .asSequence()
-            .filter { it.type.isInstance(this) }
-            .sortedWith(CompareGenericWrappers)
-            .firstOrNull()
-            ?.transformer?.invoke(this, environment.get()) ?: this
+    /**
+     * Function that returns the object used to fetch the data. It can be a DataFetcher or an entity.
+     */
+    @Suppress("unused")
+    fun getWrappedFetchingObject(environment: DataFetchingEnvironment): Any {
+        return sourceResolver.resolve(environment, null)
     }
 }
 
+private fun Any.transformWithGenericWrapper(
+    genericWrappers: List<GenericWrapper>,
+    environmentSupplier: Supplier<DataFetchingEnvironment>
+): Any? {
+    return genericWrappers
+        .asSequence()
+        .filter { it.type.isInstance(this) }
+        .sortedWith(CompareGenericWrappers)
+        .firstOrNull()
+        ?.transformer?.invoke(this, environmentSupplier.get()) ?: this
+}
+
 private class CompareGenericWrappers {
     companion object : Comparator<GenericWrapper> {
         override fun compare(w1: GenericWrapper, w2: GenericWrapper): Int = when {
@@ -288,6 +280,14 @@ private class CompareGenericWrappers {
     }
 }
 
+private fun Method.isSuspendFunction(): Boolean {
+    return try {
+        this.kotlinFunction?.isSuspend == true
+    } catch (e: InternalError) {
+        false
+    }
+}
+
 private suspend inline fun invokeSuspend(target: Any, resolverMethod: Method, args: Array<Any?>): Any? {
     return suspendCoroutineUninterceptedOrReturn { continuation ->
         invoke(resolverMethod, target, args + continuation)