Working with a task created by maven-publish pulication.

build.gradle

apply plugin: 'java'

apply plugin: 'maven-publish'

task sourceJar(type: Jar) {
    from sourceSets.main.allJava
}

task dummy << {

}

publishing {
    publications {
        mavenJava(MavenPublication) {
            from components.java

            artifact sourceJar {
                classifier "sources"
            }
        }
    }
}

afterEvaluate {
  publishMavenJavaPublicationToMavenLocal {
    dependsOn(dummy)

    doFirst {
      println "Does this work?"
    }
  }
}