An example for how to use publication variants to gather files from tasks in projects. This is the full example for my StackOverflow answer about aggregating JaCoCo reports.
The question boils down to:
How can I gather individual JaCoCo reports from sub projects into one folder in the root project
The solution comprises of two steps:
The idea is to have a pre-compiled script plugin in buildSrc/src/main/kotlin/jacoco-conventions.gradle.kts that configures JaCoCo.
The plugin defines a custom configuration called jacocoReports.
jacocoReports is consumable, meaning other projects can depend on it, but we can not get files by declaring dependencies in this configuration inside the dependencies block.
It has a USAGE_ATTRIBUTE set to jacocoReports which is needed to consume it from other projects.
Last but not least the outgoing artifacts of this configuration are the JaCoCo XML reports.
Since we want the reports to be created when the configuration is consumed, we need to tell the configuration which task creates the outgoing artifact.
This tells Gradle to call the jacocoTestReport task when the jacocoReports configuration is consumed.
In order to gather the the reports in the root project we need to create a configuration that consumes the jacocoReports publication variants.
This is what the jacocoReports configuration in build.gradle.kts does.
This time the configuration is not consumable, but resolvable, meaning that we can get the files that are in this configuration by resolving it.
Furthermore the jacocoReports configuration has the USAGE_ATTRIBUTE set to jacocoReports.
This why when we define a dependency in jacocoReports to another project it will use this variant.
The next step is to define project dependencies using the jacocoReports configuration.
Then we can have a simple copy task that copies the files from the jacocoReports configuration the the destination directory.
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This code is open source software licensed under the Apache 2.0 License.