Do not finalize the value of the properties of a task that is skipped

[adammurdoch]

#7371 added support to finalize the value of certain task input and output properties when the task starts execution. However, this finalization can be expensive and is pointless for many properties of a task that is skipped.

For example, finalizing the compile classpath for a compile task may involve a bunch of network access to resolve dependencies, however the value will be ignored if the task has no source files to compile and is skipped.

Expected Behavior

Finalize the value of only those properties of a task that are required to decide whether a task should be skipped. Only if the task will proceed should the remaining properties be finalized.

We should probably do the same with the "get from cache or run task actions" decision, and only finalize properties such as local state properties after we've decided to run the task actions.

The implementation might simply be to set all task properties to "finalize on next query" early in the execution lifecycle, so they are finalized only as required by whatever needs the value.

Current Behavior

Gradle does too much work when skipping tasks.

[lptr]

We already don't finalize inputs for tasks that are skipped early via onlyIf() or -x. I think this is only about primary inputs (@SkipWhenEmpty) that should be finalized first, checked if we can skip the task, and only then we should continue finalizing the rest of the inputs.

Is there another case we need to care about here?

[adammurdoch]

I think we should just limit this issue to @SkipWhenEmpty properties.

Longer term, we should finalize and validate any properties needed to evaluate onlyIf(), then do the same for @SkipWhenEmpty properties if we need to (including any internal properties needed to calculate the values of these properties), then do the same for the properties we need for the cache key, then finally the properties we need to run the task actions.

[lptr]

That's a good point: we should always validate any property that has been finalized.

[adammurdoch]

I want to look at task property validation as part of #4468, so that validation is triggered in some way by finalizing the value.

[stale]

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[stale]

This issue has been automatically closed due to inactivity. If you can reproduce this on a recent version of Gradle or if you have a good use case for this feature, please feel free to reopen the issue with steps to reproduce, a quick explanation of your use case or a high-quality pull request.