Gradle: Common Zip task for every subproject

Question

I have a multi-project gradle build, where all subprojects of root project have common zip task. They should zip some source, depending of the subproject's settings.

First, I configured it in parent build.gradle:

subprojects { subproject ->
    apply plugin: 'java'
    ...

    task submission(type: Zip) { 
        destinationDir = subproject.buildDir
        archiveName = subproject.name

        from subproject.ext.submissionFiles
    }
}

But this does not work with Cannot get property 'submissionFiles' on extra properties extension as it does not exist. So i moved the task in each subproject's build.gradle, which breaks DRY principle.

I think the problem is that the configuration phase takes place before subprojects are configured. How can I "defer" configuration of this task, so that I only configure ext.submissionFiles in subprojects?

Answer 1

I think you're saying that submissionFiles is set in the subproject's build.gradle?

There are a few ways of doing it.

Option 1. You could defer the evaluation of subproject.ext.submissionFiles by wrapping it in a closure:

task submission(type: Zip) { 
    destinationDir = subproject.buildDir
    archiveName = subproject.name

    from ({ subproject.ext.submissionFiles })
}

---

Option 2. I think it could be better if you didn't use the intermediate variable (submissionFiles) and directly configured the submission task in the children:

// In root
task submission(type: Zip) { 
    destinationDir = subproject.buildDir
    archiveName = subproject.name
}

// In child
submission {
    from("path/to/files")
}

Using an intermediate variable like that to move configuration around can make your builds harder to understand connections between tasks.

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Option 3. In some cases, it makes sense to use evaluationDependsOnChildren(), but I would generally not recommend it.