Question

To explain my problem in the simplest way, I’ll first show you a Groovy script that does work and then add some Gradle sauce which breaks it.

The working script:

class MyMixin {
    String myname = 'max'
}

@Mixin(MyMixin)
class MyClass {}

MyClass c = new MyClass()
println 'hello ' + c.myname

This prints out “hello max” as expected. Now let’s replace that MyClass with a Gradle task class. For this we extend DefaultTask and use the @TaskAction annotation.

@Mixin(MyMixin)
class MyTask extends DefaultTask {

    @TaskAction
    void sayHello() {
        println 'hello ' + myname
    }
}

If we now install this Gradle task and execute it, we get the following runtime error:

Execution failed for task ':myproject:mytask'.
> MyTask.getMyname()Ljava/lang/String;

What’s funny is that this only happens with methods returning something. void methods execute just fine.

So the question is simple: how can I get my mixin to cooperate with my Gradle task? (FYI: it doesn’t seem to be related to inheritance; I checked that, but didn’t include it in the sample script to keep it simple. I have also tested with a runtime mixin instead of compile-time: the result is the same).

Answer 1

I posted the same question on the Gradle forum and according to the Gradle developers it is an incompatibility between Groovy’s @Mixin and Gradle’s own meta-programming facilities. They suggest to use Gradle’s extra properties and/or extension objects instead.

For reference: http://forums.gradle.org/gradle/topics/groovy_mixin_combined_with_gradle_defaulttask_results_in_runtime_error