New Task Cycle with Gradle 5.6 Nightly

Hi, we have a custom plugin that works fine up to gradle 5.5 but with the gradle 5.6 nightly it fails

we get an error message like this

	FAILURE: Build failed with an exception.

* What went wrong:
Circular dependency between the following tasks:
\--- :compileJava
     \--- :generateXtext
          \--- :classes (*)

(*) - details omitted (listed previously)

i have no idea what could cause this.
is there any option or hint to find out where in the plugin the cycle is established?

you can find the sample project here:


i think i at least have a hint

we do something like that:

generatorTask.classesDirs = generatorTask.classesDirs ?: javaSourceSet.output.classesDir

and mark

@Accessors @Input @Optional FileCollection classesDirs

=> but why is this considered a cycle if we just copy over stuff

maybe it should be

generatorTask.classesDirs = generatorTask.classesDirs ?: javaSourceSet.output.dirs

but that is not working

=> how can i read and reuse classesDirs?

i now removed the


and it seems to work