Extract resolver parameter count into a util

Count JVM parameters minus the suspend Continuation instead of going
through kotlin-reflect's parameter list, and read the last parameter
from parameterTypes at that index.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: oryan-block

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

@@ -16,9 +16,7 @@ import org.apache.commons.lang3.reflect.TypeUtils
 import org.reactivestreams.Publisher
 import org.slf4j.LoggerFactory
 import java.lang.reflect.*
-import kotlin.reflect.KParameter
 import kotlin.reflect.full.extensionReceiverParameter
-import kotlin.reflect.jvm.javaType
 import kotlin.reflect.jvm.kotlinFunction
 
 /**
@@ -172,31 +170,14 @@ internal class FieldResolverScanner(val options: SchemaParserOptions) {
             !isExtensionFunction(method)
         }
 
-        val methodParameterCount = getMethodParameterCount(method)
-        val methodLastParameter = getMethodLastParameter(method)
+        val methodParameterCount = method.parameterCountWithoutContinuation()
+        val methodLastParameter = method.parameterTypes.getOrNull(methodParameterCount - 1)
 
         val correctParameterCount = methodParameterCount == requiredCount ||
             (methodParameterCount == (requiredCount + 1) && allowedLastArgumentTypes.contains(methodLastParameter))
         return correctParameterCount && appropriateFirstParameter
     }
 
-    private fun getMethodParameterCount(method: Method): Int {
-        return try {
-            method.kotlinFunction?.parameters?.count { it.kind != KParameter.Kind.INSTANCE } ?: method.parameterCount
-        } catch (e: InternalError) {
-            method.parameterCount
-        }
-    }
-
-    private fun getMethodLastParameter(method: Method): Type? {
-        return try {
-            method.kotlinFunction?.parameters?.lastOrNull { it.kind != KParameter.Kind.INSTANCE }?.type?.javaType
-                ?: method.parameterTypes.lastOrNull()
-        } catch (e: InternalError) {
-            method.parameterTypes.lastOrNull()
-        }
-    }
-
     private fun isExtensionFunction(method: Method): Boolean {
         return try {
             method.kotlinFunction?.extensionReceiverParameter != null

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

@@ -7,6 +7,8 @@ import graphql.kickstart.tools.SchemaParserOptions.GenericWrapper
 import graphql.kickstart.tools.util.JavaType
 import graphql.kickstart.tools.util.coroutineScope
 import graphql.kickstart.tools.util.futureValueType
+import graphql.kickstart.tools.util.isSuspendFunction
+import graphql.kickstart.tools.util.parameterCountWithoutContinuation
 import graphql.kickstart.tools.util.typeArgument
 import graphql.kickstart.tools.util.unwrap
 import graphql.language.*
@@ -26,7 +28,6 @@ import java.lang.reflect.Method
 import java.util.*
 import java.util.function.Supplier
 import kotlin.coroutines.intrinsics.suspendCoroutineUninterceptedOrReturn
-import kotlin.reflect.KParameter
 import kotlin.reflect.jvm.javaType
 import kotlin.reflect.jvm.kotlinFunction
 
@@ -43,7 +44,7 @@ internal class MethodFieldResolver(
     private val log = LoggerFactory.getLogger(javaClass)
 
     private val isSuspendFunction = method.isSuspendFunction()
-    private val numberOfParameters = method.kotlinFunction?.parameters?.count { it.kind != KParameter.Kind.INSTANCE } ?: method.parameterCount
+    private val numberOfParameters = method.parameterCountWithoutContinuation()
     private val hasAdditionalParameter = numberOfParameters == (field.inputValueDefinitions.size + getIndexOffset() + 1)
 
     override fun createDataFetcher(): DataFetcher<*> {
@@ -283,14 +284,6 @@ 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)

src/main/kotlin/graphql/kickstart/tools/util/Utils.kt

@@ -12,6 +12,7 @@ import java.lang.reflect.ParameterizedType
 import java.lang.reflect.Proxy
 import java.util.concurrent.CompletionStage
 import java.util.concurrent.Future
+import kotlin.reflect.jvm.kotlinFunction
 
 /**
  * @author Andrew Potter
@@ -59,6 +60,18 @@ internal val Class<*>.declaredNonProxyMethods: List<JavaMethod>
         }
     }
 
+internal fun JavaMethod.isSuspendFunction(): Boolean {
+    return try {
+        this.kotlinFunction?.isSuspend == true
+    } catch (e: InternalError) {
+        false
+    }
+}
+
+// the trailing Continuation of a suspend function isn't a resolver argument
+internal fun JavaMethod.parameterCountWithoutContinuation(): Int =
+    if (isSuspendFunction()) parameterCount - 1 else parameterCount
+
 internal fun getDocumentation(node: AbstractNode<*>, options: SchemaParserOptions): String? =
     when {
         node is AbstractDescribedNode<*> && node.description != null -> node.description?.content