Jacoco offline instrumentation in gradle

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I had a need to do this too and was able to figure out how to hack the jacoco plugin to do offline instrumentation:

//Additional SourceSets can be added to the jacocoOfflineSourceSets as needed by 
project.ext.jacocoOfflineSourceSets = [ 'main' ]
task doJacocoOfflineInstrumentation(dependsOn: [ classes, project.configurations.jacocoAnt ]) {
    inputs.files classes.outputs.files
    File outputDir = new File(project.buildDir, 'instrumentedClasses')
    outputs.dir outputDir
    doFirst {
        project.delete(outputDir)
        ant.taskdef(
            resource: 'org/jacoco/ant/antlib.xml',
            classpath: project.configurations.jacocoAnt.asPath,
            uri: 'jacoco'
        )
        def instrumented = false
        jacocoOfflineSourceSets.each { sourceSetName ->
            if (file(sourceSets[sourceSetName].output.classesDir).exists()) {
                def instrumentedClassedDir = "${outputDir}/${sourceSetName}"
                ant.'jacoco:instrument'(destdir: instrumentedClassedDir) {
                    fileset(dir: sourceSets[sourceSetName].output.classesDir, includes: '**/*.class')
                }
                //Replace the classes dir in the test classpath with the instrumented one
                sourceSets.test.runtimeClasspath -= files(sourceSets[sourceSetName].output.classesDir)
                sourceSets.test.runtimeClasspath += files(instrumentedClassedDir)
                instrumented = true
            }
        }
        if (instrumented) {
            //Disable class verification based on https://github.com/jayway/powermock/issues/375
            test.jvmArgs += '-noverify'
        }
    }
}
test.dependsOn doJacocoOfflineInstrumentation