Output path is shared between the same module error

Question

When I try to compile any class in my project I get the error below:

Error scala: Output path .../eval/target/test-classes is shared between: Module \'eval\' tes         


        

Answer 1

I had this happen with the root module in a multi-module project. Since the root module was just a placeholder, it didn't actually contain any code, but IDEA still complained that it was sharing an output path ([project]/build) between test and production.

The fix was to add

plugins {
  id "java"
}

at the top of the root build.gradle file (applying the otherwise unnecessary Java plugin) and reimporting the project. This allowed IDEA to pick up the Java-default [project]/build/classes/main and [project]/build/classes/test output directories.