Build ignores Kotlin changes with Retrolambda 3.1.0

Here’s a test project: https://github.com/cypressious/KotlinRetrolambdaBug

Run the app. The activity should display “bar”. Now go to com.cypressworks.kotlinretrolambdatest.Foo and change "bar to “foo”. Run the app again. You will see “bar” again.

Gradle prints:

:app:compileDebugKotlin
:app:compileDebugJava UP-TO-DATE
:app:compileRetrolambdaDebug
:app:compileDebugNdk UP-TO-DATE
:app:compileDebugSources UP-TO-DATE
:app:preDexDebug UP-TO-DATE
:app:dexDebug UP-TO-DATE
:app:validateDebugSigning
:app:packageDebug UP-TO-DATE
:app:zipalignDebug UP-TO-DATE
:app:assembleDebug UP-TO-DATE

Notice how, despite compileDebugKotlin and compileRetrolambdaDebug being not up-to-date, the rest of the tasks was skipped?

[cypressious]

Here’s a version of @sfunke’s workaround that’s more generic (works with flavors) and possibly a bit faster:

project.afterEvaluate {
    def variants = project.android.applicationVariants + project.android.testVariants

    variants.each { var ->
        def kotlinTask = tasks["compile${var.name.capitalize()}Kotlin"]

        kotlinTask.doLast {
            println "########"
            println "Dynamically reset compile${var.name.capitalize()}Java's UP-TO-DATE flag"
            println "########"
            tasks["compile${var.name.capitalize()}Java"].outputs.upToDateWhen { false }
        }
    }
}

Seems to also work with JRebel for Android.

EDIT: In version 1.3.0 of the Android Gradle plugin, the task name seems to have changed to compile${var.name.capitalize()}JavaWithJavac.

[sfunke]

If anyone is interested, my workaround, based on @cypressious 's inspiration and my own limited gradle knowledge. (Just relates to debug build variant, but fits my needs very well.)

I am able to use latest retrolambda gradle plugin (3.2.0)

project.afterEvaluate {
    def tasks = it.tasks
    tasks.each {
        // println "=== afterEvaluate: $it.name"
        if(it.name == "compileDebugKotlin") {
            it.doLast {
                println "########"
                println "Dynamically reset compileDebugJava's UP-TO-DATE flag"
                println "########"
                tasks["compileDebugJava"].outputs.upToDateWhen {false}
            }
        }
    }
}

Explanation: As project is being evaluated, an execution block is added to the compileDebugKotlin task, so whenever that task is run (and our java classes are considered dirty), the compileDebugJava task’s output upToDate-flag is set to false (so compileDebugJava is being forced to run).

Hacky and raw, but gets the job done.