Task outputs based on dependent task outputs

Help/Discuss
1

Hi all,

I’ve done some searching in Gradle docs and previous discussions and I haven’t been able to find an answer to this. I hope it’s a simple question.

I have a Task A which depends on Task B and Task C. All these tasks are custom with specified inputs and outputs.

task A (dependsOn: [ 'B', 'C']) {
      ...
}

I want the output for A to be an aggregation of outputs from B+C, but I haven’t been able to work out how to do that.

This seems like it should have a simple and obvious solution that I’m just not seeing. Any help is appreciated.

2

So this is the only thing I’ve been able to get to work. I’m sure there must be an easier way to do this that I’m not getting.

task A( dependsOn:[B, C]) {
    outputs.dir B.outputs.files.filter( f->{ f.directory })
    outputs.dir C.outputs.files.filter( f->{ f.directory })
    outputs.files B.outputs.files.filter( f->{ f.file })
    outputs.files C.outputs.files.filter( f->{ f.file })
}
3

The actual answer is, do not even try to do that.
You should never have overlapping task outputs.
Instead make A a task of type Sync, copying from B and C to some dedicated destination directory.
This way you also do not need an explicit dependsOn which is bad practice except for lifecycle tasks.
So you want something like

tasks.register('A', Sync) {
    from(B)
    from(C)
    into(layout.buildDirectory.dir('a')
}
4

Thanks, @Vampire. I played around a little further and came to the same conclusion. Clearly, I was trying to swim against the current with this idea. Always a signal that there’s an easier, different approach.

5

Is tasks.register preferred for gradle these days over a task declaration (as in my example)? Is there a short explanation as to why?

6

task A is syntactic sugar for tasks.create('A') which is against task configuration avoidance: Task Configuration Avoidance

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