Copy(Jar) custom plugin to call "into ..., { from ... }" from configurations

Help/Discuss
1

Hi,

I’m trying a custom plugin with a task extending Jar, which is to import a part of resource files into a subdirectory. The directory would be specified from configuration.

// build.gradle configuration for the task I'd like to make
configurations {
    target
}

myJar {
    targetResourceInto 'subdir'
}

// Example plugin code to show the point
import org.gradle.api.tasks.TaskAction
import org.gradle.api.tasks.bundling.Jar

class MyJar extends Jar {
    MyJar() {
        // targetResourceInto is not configured yet...
        with project.jar
    }

    @TaskAction @Override void copy() {
        into targetResourceInto, {
            from {
                project.configurations.target
            }
        }
    }

    String targetResourceInto
}

But, it fails from Gradle 4 with:

> You cannot add child specs at execution time. Consider configuring this task during configuration time or using a separate task to do the configuration.

I understand the message that I need to set before @TaskAction void copy(). But, the constructor is too early to read the configuration targetResourceInto…

Could anyone advice how this problem can be solved?

2

An example code set is at: https://github.com/dmikurube/discuss.gradle.org-24083

$ ./gradlew myJar

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':myJar'.
> You cannot add child specs at execution time. Consider configuring this task during configuration time or using a separate task to do the configuration.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

* Get more help at https://help.gradle.org

BUILD FAILED in 2s
1 actionable task: 1 executed



$ ./gradlew localJar

BUILD SUCCESSFUL in 1s
2 actionable tasks: 2 executed



$ unzip -l build/libs/test-target.jar 
Archive:  build/libs/test-target.jar
  Length     Date   Time    Name
 --------    ----   ----    ----
        0  09-15-17 00:25   META-INF/
       25  09-15-17 00:25   META-INF/MANIFEST.MF
        0  09-15-17 00:25   localjardir/
   314932  07-27-17 12:12   localjardir/junit-4.12.jar
    45024  10-26-16 15:57   localjardir/hamcrest-core-1.3.jar
      507  09-15-17 00:25   Main.class
 --------                   -------
   360488                   6 files
3

jfyi, I’ve checked that into(value).from(value) (without closures) does not work as intended. (It moves “all” (including Main.class) into the subdirectory, not just a part.)

4

Jfyi2, hooking targetResourceInto (like setTargetResourceInto(...)) actually does not work for my specific case because the behavior needs to switch whether targetResourceInto is configured or not. (Not programmed in the example, though.)

5

Another way to approach this is to have your plugin add a task extension to the Jar class which will change your DSL to:

configurations {
  target
}

jar {
  targetResources {
    into 'subdir'
  }
}

Your physical code will be something like

class JarExtension {
  JarExtension( Jar task ) {
    this.task = task
  }

  void into(final String subdir) {
    task.into (subdir), {
      from task.project.configurations.getByName('target')
    } 
  }

  private Jar task
}

and in the plugin apply code

void apply(Project project) {
  projects.tasks.withType(Jar) { task ->
    task.extensions.create( 'targetResource', JarExtension, task )
  }
  project.tasks.whenTaskAdded { task ->
    if(task instanceof Jar) {
       // ... as above 
    }
  }
}

This approach can sometimes provide a cleaner DSL

6

Thanks, but the purposes of this were

  1. to provide a totally independent task for this type of JAR without contaminating the original “jar” task
  2. to provide a simple syntax to build.gradle writers who are building such special JAR files.

I’ve finally solved this by myself with moving everything into project.afterEvaluate in the constructor like:

class MyJar extends Jar {
    MyJar() {
        super()
        // targetResourceInto is not configured yet...
        project.afterEvaluate {
            into targetResourceInto, {
                from {
                    project.configurations.target
                }
            }
            with project.jar
        }
    }

    @TaskAction @Override void copy() {
        super.copy()
    }

    String targetResourceInto
}

Thanks.