Exceptions in @OutputFiles method can hang Gradle 4.0 without reporting the exceptions

[rkrisztian]

This is related to #2406, where we discussed that the use case wasn't valid, however, this time, I think it is important to fix regardless of the use case.

Expected Behavior

Gradle 4.0 should not hang when a Task method annotated with @OutputFiles throws any kind of exception.

Current Behavior

I executed gw myPreceedingTask --stacktrace --info with the example build script below, and I was expecting an NPE to be reported.

> Task :myPreceedingTask
Putting task artifact state for task ':myPreceedingTask' into context took 0.0 secs.
Executing task ':myPreceedingTask' (up-to-date check took 0.0 secs) due to:
  Task has not declared any outputs.
Hello from myPreceedingTask!

:myPreceedingTask (Thread[Task worker Thread 2,5,main]) completed. Took 0.014 secs.
<======-------> 50% EXECUTING [4m 6s]
> IDLE
^C

It just does not terminate.

I did some debugging, and found that the related code part that is interesting for us is org.gradle.execution.taskgraph.DefaultTaskExecutionPlan#executeWithTask:

                    try {
                        selected.set(DefaultTaskExecutionPlan.this.selectNextTask(workerLease));
                    } catch (Throwable var3) {
                        DefaultTaskExecutionPlan.this.abortAndFail(var3);
                        workRemaining.set(false);
                    }

where:

    private void abortAndFail(Throwable t) {
        this.abortExecution();
        this.failures.add(t);
    }

where:

    private boolean abortExecution() {
        boolean aborted = false;
        Iterator i$ = this.executionPlan.values().iterator();

        while(i$.hasNext()) {
            TaskInfo taskInfo = (TaskInfo)i$.next();
            if(taskInfo.isRequired()) {
                taskInfo.skipExecution();
                aborted = true;
            }
        }

        return aborted;
    }

Then, TaskInfo.isRequired is false for both :myTestTask and :myPreceedingTask, causing the build to hang. I think one of those should still be required.

If I replace the association from myPreceedingTask.finalizedBy myTestTask to myPreceedingTask.dependsOn myTestTask, then I get the right error message and the build terminates.

Context

In my actual code, the task that I represented here with myTestTask, is actually not a finalizer, but I have no idea why it is not required in the TaskInfo.

Steps to Reproduce (for bugs)

This time my gradle.build looks like this:

group 'myTest'
version '1.0-SNAPSHOT'

task wrapper(type: Wrapper) {
	gradleVersion = '4.0'
	distributionUrl = "https://services.gradle.org/distributions/gradle-$gradleVersion-all.zip"
}

apply plugin: 'groovy'

repositories {
	mavenCentral()
}

dependencies {
	compile gradleApi()
	compile 'org.codehaus.groovy:groovy-all:2.4.11'
}

class MyTestTask extends DefaultTask {
	MyTestTask() {
		outputs.upToDateWhen { false }
	}

	@OutputFiles
	List<File> getMyOutputs() {
		throw new NullPointerException('my exception')
	}

	@TaskAction
	void printHello() {
		println 'Hello from myTestTask!'
	}
}

task myPreceedingTask {
	doLast {
		println 'Hello from myPreceedingTask!'
	}
}

task myTestTask(type: MyTestTask) {
}

myPreceedingTask.finalizedBy myTestTask

Your Environment

Still shouldn't matter.

[ghale]

@rkrisztian Thanks for reporting. This is indeed a bug. That logic is intended to allow finalizer tasks to run when task execution fails, but when we have a failure while walking the task graph, we should abort all tasks. We'll get this fixed.

[eriwen]

@ghale I'm going to close this as complete and will be delivered in 4.0.2 next week.