What's left to make this work

[nedtwigg]

There are two open questions:

1. Does gradle let you disable a task during task execution? That's our whole premise, so hopefully the answer to this is yes!

cache-horizon/src/main/java/com/diffplug/cachehorizon/CacheHorizonPlugin.java

Lines 131 to 135 in 13424bc

	if (isCachedOrUpToDate(horizonTask.get())) {
	for (Provider<? extends Task> innerProvider : innerTasks) {
	Task innerTask = innerProvider.get();
	innerTask.setEnabled(false);
	}

2. How can we implement boolean isCachedOrUpToDate(Task task)?

This is how far we got, by copying out the relevant-looking parts of Gradle's task execution. It definitely doesn't work as written, but it points towards the internal APIs that Gradle uses for this.

cache-horizon/src/main/java/com/diffplug/cachehorizon/CacheHorizonPlugin.java

Lines 139 to 203 in 13424bc

	private boolean isCachedOrUpToDate(Task task) {
	TaskExecutionGraphInternal graph = (TaskExecutionGraphInternal) getProject().getGradle().getTaskGraph();
	for (Node node : graph.getScheduledWork()) {
	if (node instanceof LocalTaskNode) {
	LocalTaskNode localTaskNode = (LocalTaskNode) node;
	if (localTaskNode.getTask() == horizonTask) {
	return isCachedOrUpToDate(localTaskNode);
	}
	}
	}
	return false;
	}
	private boolean isCachedOrUpToDate(LocalTaskNode localTaskNode) {
	ServiceRegistry registry = ((ProjectInternal) getProject()).getServices();
	BuildOperationExecutor buildOperationExecutor = registry.get(BuildOperationExecutor.class);
	ClassLoaderHierarchyHasher classLoaderHierarchyHasher = registry.get(ClassLoaderHierarchyHasher.class);
	ValueSnapshotter valueSnapshotter = registry.get(ValueSnapshotter.class);
	OverlappingOutputDetector overlappingOutputDetector = registry.get(OverlappingOutputDetector.class);
	BuildCacheController buildCacheController = registry.get(BuildCacheController.class);
	boolean buildScansEnabled = false;
	DefaultWorkExecutor<ExecutionRequestContext, CachingResult> executor = new DefaultWorkExecutor<>(
	new LoadExecutionStateStep<>(
	new CaptureStateBeforeExecutionStep(buildOperationExecutor, classLoaderHierarchyHasher, valueSnapshotter, overlappingOutputDetector,
	new ResolveCachingStateStep(buildCacheController, buildScansEnabled, new Step<CachingContext, UpToDateResult>() {
	@Override
	public UpToDateResult execute(CachingContext context) {
	return new UpToDateResult() {
	@Override
	public ImmutableSortedMap<String, ? extends FileCollectionFingerprint> getFinalOutputs() {
	throw new UnsupportedOperationException();
	}
	@Override
	public Try<ExecutionOutcome> getOutcome() {
	throw new UnsupportedOperationException();
	}
	@Override
	public ImmutableList<String> getExecutionReasons() {
	throw new UnsupportedOperationException();
	}
	@Override
	public Optional<OriginMetadata> getReusedOutputOriginMetadata() {
	throw new UnsupportedOperationException();
	}
	};
	}
	}))));
	CachingResult caching = executor.execute(new ExecutionRequestContext() {
	@Override
	public Optional<String> getRebuildReason() {
	throw new UnsupportedOperationException();
	}
	@Override
	public UnitOfWork getWork() {
	throw new UnsupportedOperationException();
	}
	});
	ExecutionOutcome outcome = caching.getOutcome().get();
	return outcome == ExecutionOutcome.FROM_CACHE || outcome == ExecutionOutcome.UP_TO_DATE;
	}

That's as far as we got, and as far as we are likely to get for the foreseeable future. We're happy to merge PRs and add committers here if you don't want to deal with publishing and maintaining, also we're also happy to shut this project down and link to yours if you find a way forward and want to maintain it.

Our intent is to use this issue as the "forum" for solving the two questions above, or for linking out to other solutions that frame the problem differently.