Gradle Task messes with runtime Dependencies - gradle

Question

Another strange behaviour of gradle...
So I've found this post:
Gradle exclude module for Copy task
Totally fine and works like a charm to exclude things from copying.
But here is where it gets interesting. This is how my Copy Task looks:
task copyDependencies(type: Copy) {
into "$buildDir/libs/dependencies"
from configurations.runtime {
exclude module: 'groovy'
exclude module: 'aws-java-sdk-s3'
exclude module: 'commons-io'
}
}
If I try to run the Application through Gradles 'application run' task. It fails with "Main Class xxx couldn't be found or loaded". Digging deeper into the problem I noticed that Groovy couldn't be resolved.
I don't even run this Task, or depend on it.
But if I comment out line 4 like this:
task copyDependencies(type: Copy) {
into "$buildDir/libs/dependencies"
from configurations.runtime {
//exclude module: 'groovy'
exclude module: 'aws-java-sdk-s3'
exclude module: 'commons-io'
}
}
The Application starts like normal, until it reaches a point where it needs Commons-IO. I still want to use this copyDependencies Task at other times, without changing the code there though.
Can somebody explain me this behaviour ?
I imagine manipulating the configuration.runtime anywhere in the gradle file, changes it for every other task ?

Answer 1

In your from configuration block, you are referencing the runtime configuration, but in the same time you are altering this configuration by adding some exclusion rules. This will alter the original (and unique) runtime configuration which will be used by all other tasks in your build project, as you have guessed. This explains the "Main Class xxx couldn't be found or loaded" error you get when trying to execute the run task, since the runtime configuration (classpath) does not contain the needed library.
If you want to write exclusions rules by group and/or module in your copyDependencies task, one possible way would be to work on a copy of the original runtime configuration; you could define a new Configuration for this purpose:
configurations{
runtimeDeps.extendsFrom runtime
}
task copyDependencies(type: Copy) {
into "$buildDir/libs/dependencies"
from configurations.runtimeDeps {
exclude module: 'groovy'
exclude module: 'aws-java-sdk-s3'
exclude module: 'commons-io'
}
}