Java 11がリリースされたので早速試したら、問題が出たのでメモ。

なお、2018/09/26現在、GradleはまだJava 11をサポートしてません。
以下のissueで進行中です。

Java 11 support

2018/10/11 追記

2018/10/03にGradle 5.0 Milestone 1がリリースされました。
5.0 Milestone 1では、この記事の問題は再現しなくなった事を確認しました。

サンプルソースは更新済です。
https://github.com/matsumana/gradle-jdk11-sandbox

Upgradeコマンドはこちら

$ ./gradlew wrapper --gradle-version=5.0-milestone-1

リリースノートはこちら

4.xからの移行ガイドはこちら

https://docs.gradle.org/5.0-milestone-1/userguide/upgrading_version_4.html

使用したバージョン

JDK: OpenJDK 11 GA (build 28)

openjdk version "11" 2018-09-25
OpenJDK Runtime Environment 18.9 (build 11+28)
OpenJDK 64-Bit Server VM 18.9 (build 11+28, mixed mode)

Gradle: 4.10.2

サンプルソース

今回の現象を再現させるためのサンプルソースは以下に置いておきました
https://github.com/matsumana/gradle-jdk11-sandbox

現象

テストソースの中にネストしたクラスを定義していると、Gradleのtestタスク実行時に例外が発生します。

例えば、以下のようなソース。
なお、IntelliJからは問題なく実行できます。

package com.example.demo;

import static org.junit.jupiter.api.Assertions.assertTrue;

import org.junit.jupiter.api.Test;

public class SampleTest {

    public static class NestClass {
        private String field1;

        public String getField1() {
            return field1;
        }

        public void setField1(String field1) {
            this.field1 = field1;
        }
    }

    @Test
    public void test() throws Exception {
        assertTrue(true);
    }
}

スタックトレース

$ ./gradlew clean build --stacktrace
> Task :test FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':test'.
> failed to read class file //tmp/gradle-jdk11-sandbox/gradle-jdk11-sandbox/build/classes/java/test/com/example/demo/SampleTest$NestClass.class

* Try:
Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':test'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:110)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:77)
        at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:101)
        at org.gradle.api.internal.tasks.execution.FinalizeInputFilePropertiesTaskExecuter.execute(FinalizeInputFilePropertiesTaskExecuter.java:44)
        at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:91)
        at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:62)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:59)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter$1.run(EventFiringTaskExecuter.java:51)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.api.internal.tasks.execution.EventFiringTaskExecuter.execute(EventFiringTaskExecuter.java:46)
        at org.gradle.execution.taskgraph.LocalTaskInfoExecutor.execute(LocalTaskInfoExecutor.java:42)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareWorkItemExecutor.execute(DefaultTaskExecutionGraph.java:277)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph$BuildOperationAwareWorkItemExecutor.execute(DefaultTaskExecutionGraph.java:262)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$ExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:135)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$ExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:130)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$ExecutorWorker.execute(DefaultTaskPlanExecutor.java:200)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$ExecutorWorker.executeWithWork(DefaultTaskPlanExecutor.java:191)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$ExecutorWorker.run(DefaultTaskPlanExecutor.java:130)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:74)
        at org.gradle.execution.taskgraph.DefaultTaskExecutionGraph.execute(DefaultTaskExecutionGraph.java:143)
        at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:40)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:40)
        at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:24)
        at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:46)
        at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:49)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:40)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:33)
        at org.gradle.initialization.DefaultGradleLauncher$ExecuteTasks.run(DefaultGradleLauncher.java:355)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.initialization.DefaultGradleLauncher.runTasks(DefaultGradleLauncher.java:219)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:149)
        at org.gradle.initialization.DefaultGradleLauncher.executeTasks(DefaultGradleLauncher.java:124)
        at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:77)
        at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:74)
        at org.gradle.internal.work.DefaultWorkerLeaseService.withLocks(DefaultWorkerLeaseService.java:154)
        at org.gradle.internal.work.StopShieldingWorkerLeaseService.withLocks(StopShieldingWorkerLeaseService.java:38)
        at org.gradle.internal.invocation.GradleBuildController.doBuild(GradleBuildController.java:96)
        at org.gradle.internal.invocation.GradleBuildController.run(GradleBuildController.java:74)
        at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
        at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
        at org.gradle.tooling.internal.provider.ValidatingBuildActionRunner.run(ValidatingBuildActionRunner.java:32)
        at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner$3.run(RunAsBuildOperationBuildActionRunner.java:50)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner.run(RunAsBuildOperationBuildActionRunner.java:45)
        at org.gradle.tooling.internal.provider.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:51)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecuter.java:47)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecuter.java:44)
        at org.gradle.composite.internal.DefaultRootBuildState.run(DefaultRootBuildState.java:79)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:44)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
        at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:39)
        at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:25)
        at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:80)
        at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:53)
        at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:62)
        at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:34)
        at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:36)
        at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:25)
        at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:43)
        at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:29)
        at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:59)
        at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:31)
        at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:59)
        at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:44)
        at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:46)
        at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:30)
        at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:67)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
        at org.gradle.util.Swapper.swap(Swapper.java:38)
        at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.LogAndCheckHealth.execute(LogAndCheckHealth.java:55)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:62)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:81)
        at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
        at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:122)
        at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
        at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:295)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
Caused by: org.gradle.api.GradleException: failed to read class file //tmp/gradle-jdk11-sandbox/gradle-jdk11-sandbox/build/classes/java/test/com/example/demo/SampleTest$NestClass.class
        at org.gradle.api.internal.tasks.testing.detection.AbstractTestFrameworkDetector.classVisitor(AbstractTestFrameworkDetector.java:126)
        at org.gradle.api.internal.tasks.testing.detection.AbstractTestFrameworkDetector.processTestClass(AbstractTestFrameworkDetector.java:145)
        at org.gradle.api.internal.tasks.testing.detection.AbstractTestFrameworkDetector.processTestClass(AbstractTestFrameworkDetector.java:136)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestClassScanner$1.visitClassFile(DefaultTestClassScanner.java:58)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestClassScanner$ClassFileVisitor.visitFile(DefaultTestClassScanner.java:76)
        at org.gradle.api.internal.file.collections.jdk7.Jdk7DirectoryWalker$1.visitFile(Jdk7DirectoryWalker.java:86)
        at org.gradle.api.internal.file.collections.jdk7.Jdk7DirectoryWalker$1.visitFile(Jdk7DirectoryWalker.java:59)
        at org.gradle.api.internal.file.collections.jdk7.Jdk7DirectoryWalker.walkDir(Jdk7DirectoryWalker.java:59)
        at org.gradle.api.internal.file.collections.DirectoryFileTree.walkDir(DirectoryFileTree.java:154)
        at org.gradle.api.internal.file.collections.DirectoryFileTree.visitFrom(DirectoryFileTree.java:132)
        at org.gradle.api.internal.file.collections.DirectoryFileTree.visit(DirectoryFileTree.java:117)
        at org.gradle.api.internal.file.collections.FileTreeAdapter.visit(FileTreeAdapter.java:117)
        at org.gradle.api.internal.file.CompositeFileTree.visit(CompositeFileTree.java:93)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestClassScanner.detectionScan(DefaultTestClassScanner.java:56)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestClassScanner.run(DefaultTestClassScanner.java:50)
        at org.gradle.api.internal.tasks.testing.processors.TestMainAction.run(TestMainAction.java:55)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestExecuter.execute(DefaultTestExecuter.java:116)
        at org.gradle.api.internal.tasks.testing.detection.DefaultTestExecuter.execute(DefaultTestExecuter.java:51)
        at org.gradle.api.tasks.testing.AbstractTestTask.executeTests(AbstractTestTask.java:469)
        at org.gradle.api.tasks.testing.Test.executeTests(Test.java:603)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.doExecute(StandardTaskAction.java:46)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:39)
        at org.gradle.api.internal.project.taskfactory.StandardTaskAction.execute(StandardTaskAction.java:26)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:801)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:768)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter$1.run(ExecuteActionsTaskExecuter.java:131)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:300)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:292)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:174)
        at org.gradle.internal.operations.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.operations.DelegatingBuildOperationExecutor.run(DelegatingBuildOperationExecutor.java:31)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:120)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:99)
        ... 111 more
Caused by: java.lang.UnsupportedOperationException
        at org.objectweb.asm.ClassVisitor.visitNestHostExperimental(ClassVisitor.java:158)
        at org.objectweb.asm.ClassReader.accept(ClassReader.java:541)
        at org.objectweb.asm.ClassReader.accept(ClassReader.java:391)
        at org.gradle.api.internal.tasks.testing.detection.AbstractTestFrameworkDetector.classVisitor(AbstractTestFrameworkDetector.java:124)
        ... 147 more


* Get more help at https://help.gradle.org

BUILD FAILED in 1s
5 actionable tasks: 5 executed

Gradleはtestタスク実行時にASM使ってるんですね。知らなかった。

ちなみに、ASMは汎用のJavaバイトコード操作および分析フレームワークです。
https://asm.ow2.io/

Gradle 4.10.2が依存しているASMのバージョンは6.2です。
https://github.com/gradle/gradle/blob/v4.10.2/gradle/dependencies.gradle#L27

ASMが例外をthrowしてる箇所はこの辺です。
(ソースはGitHubじゃなくて自前のGitLabでホストしてます)
https://gitlab.ow2.org/asm/asm/blob/ASM_6_2/asm/src/main/java/org/objectweb/asm/ClassVisitor.java#L143-163

原因

Java 11からJEP 181というJEPが含まれていて、ネストクラスのバイトコードが変更になったようです。

JEP 181: Nest-Based Access Control

詳しくは、じゅくちょーさんの記事が参考になります。

以上です。