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kotlinlang

I'm a bit confused by how the plugin behaves when I try to follow the style "everything from the root package should be at the src root"

Have a look at <https://github.com/JetBrains/gradle-idea-ext-plugin/wiki/DSL-spec-v.-0.5#package-prefix-requires-idea-20191|https://github.com/JetBrains/gradle-idea-ext-plugin/wiki/DSL-spec-v.-0.5#package-prefix-requires-idea-20191> but be aware that it breaks tools like Jacoco (but Jacoco doesn't support many Kotlin things).

Yes I ended up using that. I just find it surprising to require an additional module to support the official kotlin style of package management.