Is there anything I have to do to build for java 1.8? When I added sourceCompatibility and targetCompatibility, running the build command simply fails with

Execution failed for task ':reobf'.
> java.lang.IllegalArgumentException (no error message)

And when running without them it tells me to 'use -source 8 or higher to enable ...'.

 

This is the output from using --stacktract (with sourceCompatibility and targetCompatibility being 1.8 ):

* What went wrong:
Execution failed for task ':reobf'.
> java.lang.IllegalArgumentException (no error message)

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

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':reobf'.

        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
        at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:64)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:42)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:296)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.executeTask(AbstractTaskPlanExecutor.java:79)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:63)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:51)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:23)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:86)
        at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:29)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
        at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
        at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:67)
        at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:54)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:148)
        at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:105)
        at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:85)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:81)
        at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:33)
        at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:24)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:39)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:29)
        at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:50)
        at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:171)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:237)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:210)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:35)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:24)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:206)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:169)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
        at org.gradle.launcher.Main.doAction(Main.java:33)
        at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:54)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:35)
        at org.gradle.launcher.GradleMain.main(GradleMain.java:23)
Caused by: java.lang.IllegalArgumentException
        at org.objectweb.asm.ClassReader.<init>(ClassReader.java:170)
        at org.objectweb.asm.ClassReader.<init>(ClassReader.java:153)
        at org.objectweb.asm.ClassReader.<init>(ClassReader.java:424)
        at net.md_5.specialsource.JarRemapper.remapClassFile(JarRemapper.java:228)
        at net.md_5.specialsource.JarRemapper.remapJar(JarRemapper.java:189)
        at net.minecraftforge.gradle.tasks.user.reobf.ObfArtifact.applySpecialSource(ObfArtifact.java:379)
        at net.minecraftforge.gradle.tasks.user.reobf.ObfArtifact.generate(ObfArtifact.java:348)
        at net.minecraftforge.gradle.tasks.user.reobf.ReobfTask.doTask(ReobfTask.java:298)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:63)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.doExecute(AnnotationProcessingTaskFactory.java:218)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:211)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:200)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:570)
        at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:553)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
        ... 44 more

 

I honestly have never used Gradle before, so I do apologise in advance if I'm making some sort of stupidly obvious mistake.

 

 

Edit: Just from the stack trace, I can see the error is at

if (readShort(off + 6) > Opcodes.V1_ {
            throw new IllegalArgumentException();
        }

in the ClassReader constructor. I don't actually use ASM at all, so I'm not quite sure why this is happening. I'm gonna go look at the stacktrace some more and try figure out why this is happening.

 

Edit 2: Even after looking through the ForgeGradle code on github, I'm honestly lost, as again - I've never worked with Gradle before.

Old versions of Forge aren't compatible with Java 1.8. Choose a different version and try again.

Yeah, after checking on the GitHub, the forge gradle asm API version also needs to be updated.

 

Sadly, 1.8 isn't supported (yet).

If you can convince mojang to require 1.8 java for minecraft then we will support it. But we are not going to support you breaking your mod for 80% of the community because they come to me for support.

I'd prefer to use Java 1.8 and sure its a whole "All boats rise with the same tide" issue - meaning if someone in the mod family disgarees wants to keep things at 1.6 well...expect forum comments on your mod

 

That aside, should you wish to proceed inside your build.gradle add this to your plugins area

 

apply plugin: 'java'
  compileJava {
  sourceCompatibility = '1.8'
}