removeUnusedImports does not work on Java 9

[marcphilipp]

see https://travis-ci.org/junit-team/junit5/jobs/209088615

Step 'removeUnusedImports' found problem in 'src/test/java/example/DisabledClassDemo.java':
javax/tools/JavaFileManager$Location
java.lang.NoClassDefFoundError: javax/tools/JavaFileManager$Location
	at java.lang.Class.getDeclaredMethods0(java.base@9-ea/Native Method)
	at java.lang.Class.privateGetDeclaredMethods(java.base@9-ea/Class.java:2948)
	at java.lang.Class.privateGetMethodRecursive(java.base@9-ea/Class.java:3293)
	at java.lang.Class.getMethod0(java.base@9-ea/Class.java:3263)
	at java.lang.Class.getMethod(java.base@9-ea/Class.java:1972)
	at com.diffplug.spotless.java.GoogleJavaFormatStep$State.createRemoveUnusedImportsOnly(GoogleJavaFormatStep.java:110)
	at com.diffplug.spotless.FormatterStepImpl$Standard.format(FormatterStepImpl.java:73)
	at com.diffplug.spotless.FormatterStep$Strict.format(FormatterStep.java:75)
	at com.diffplug.spotless.Formatter.compute(Formatter.java:218)
	at com.diffplug.spotless.Formatter.isClean(Formatter.java:163)
	at com.diffplug.gradle.spotless.SpotlessTask.check(SpotlessTask.java:213)
	at com.diffplug.gradle.spotless.SpotlessTask.performAction(SpotlessTask.java:169)
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(java.base@9-ea/Native Method)
	at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(java.base@9-ea/NativeMethodAccessorImpl.java:62)
	at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(java.base@9-ea/DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(java.base@9-ea/Method.java:535)
	at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:73)
	at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$IncrementalTaskAction.doExecute(DefaultTaskClassInfoStore.java:163)
	at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$StandardTaskAction.execute(DefaultTaskClassInfoStore.java:134)
	at org.gradle.api.internal.project.taskfactory.DefaultTaskClassInfoStore$StandardTaskAction.execute(DefaultTaskClassInfoStore.java:123)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:95)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:76)
	at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:55)
	at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)
	at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
	at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:88)
	at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:46)
	at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:51)
	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.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.execute(DefaultTaskGraphExecuter.java:236)
	at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.execute(DefaultTaskGraphExecuter.java:228)
	at org.gradle.internal.Transformers$4.transform(Transformers.java:169)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:106)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:61)
	at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:228)
	at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:215)
	at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:77)
	at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:58)
	at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:32)
	at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:113)
	at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
	at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
	at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
	at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
	at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
	at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
	at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
	at org.gradle.initialization.DefaultGradleLauncher$RunTasksAction.execute(DefaultGradleLauncher.java:256)
	at org.gradle.initialization.DefaultGradleLauncher$RunTasksAction.execute(DefaultGradleLauncher.java:253)
	at org.gradle.internal.Transformers$4.transform(Transformers.java:169)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:106)
	at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:56)
	at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:175)
	at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:119)
	at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:102)
	at org.gradle.launcher.exec.GradleBuildController.run(GradleBuildController.java:71)
	at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
	at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
	at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:41)
	at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:26)
	at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:75)
	at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:49)
	at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:49)
	at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:31)
	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:120)
	at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:47)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	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:120)
	at org.gradle.launcher.daemon.server.exec.LogAndCheckHealth.execute(LogAndCheckHealth.java:55)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:60)
	at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:72)
	at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
	at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
	at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
	at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:297)
	at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
	at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:46)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@9-ea/ThreadPoolExecutor.java:1161)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@9-ea/ThreadPoolExecutor.java:635)
	at java.lang.Thread.run(java.base@9-ea/Thread.java:843)
	at java.net.URLClassLoader.findClass(java.base@9-ea/URLClassLoader.java:388)
	at java.lang.ClassLoader.loadClass(java.base@9-ea/ClassLoader.java:486)
	at java.lang.ClassLoader.loadClass(java.base@9-ea/ClassLoader.java:419)
	... 95 more
:documentation:spotlessJava FAILED

[jbduncan]

I'm not entirely surprised that it failed. Spotless's removeUnusedImports feature forwards onto one provided by google-java-format, and google-java-format itself uses a custom build of OpenJDK's javac to parse source code, which itself doesn't include Jigsaw IIRC, which I suspect is causing this exception.

It's not clear to me that there's anything we can do, other than create a custom step that removes unused imports, or to find another library which lets us to remove unused imports.

[nedtwigg]

Agreed. Until google-java-format supports Java 9, this will be an unfixable bug for us. We'll update this issue when that changes.

[marcphilipp]

No worries. This is not a blocker for us at the moment. I just wanted you guys know.

[sormuras]

Class javax/tools/JavaFileManager$Location is located in module java.compiler provided by the JDK 9.

"Someone" has to declare the usage of module java.compiler somewhere:

1. google-java-format
2. spotless
3. Gradle project build configuration (here JUnit 5)
4. Gradle environment (daemon?)