How to get IDEA to detect kotlin generated sources using Gradle

So I recently got my hands on Kotlin and it's been great so far.

However one of the things that the IDEA kotlin plugin doesn't do^[1] is detect the kapt folder which contains any sources generated from annotation processing. This can be fixed using the IDEA gradle plugin^[2].

The idea plugin isn't able to mark the kapt folder as a source directory unless it's been added to the gradle source set.

sourceSets.main.java.srcDir file("$buildDir/generated/source/kapt/")

The next step is to tell the idea plugin to mark the kapt folder as a generated sources root in the module^[3].

idea {
    module {
        // Tell idea to mark the folder as generated sources
        generatedSourceDirs += file("$buildDir/generated/source/kapt/")
    }
}

When put together your build script should look a little like this.

apply plugin: 'idea'

...

kapt {
    generateStubs = true
}

// Add kapt directory to sources
sourceSets.main.java.srcDir file("$buildDir/generated/source/kapt/")

idea {
    module {
// Tell idea to mark the folder as generated sources
        generatedSourceDirs += file("$buildDir/generated/source/kapt/")
    }
}

Footnotes and references