Dependency to generated classes

Question

My multi-module project is structured like that:

Root project
|
|- MyRestApi
|
|- MyApplication

MyRestApi generates classes, which are added as a source set:

sourceSets {
    main {
        java.srcDirs += "${buildDir}/api/src/main/java/"
    }
}

MyApplication has the dependency to this code generation:

compileJava.dependsOn(':MyRestApi:generateJavaApi')

And also the dependency:

dependencies {
    implementation project(':MyRestApi')
    ....
}

So, now the problem is that the build of the root project fails, because MyApplication does not find the dependency. I suspect that the timing is wrong although the sequence of the build looks fine.

When running the builds of the submodules separately, it works. Running the root project a second time works as well.

I think it is not fast enough to find the generated classes during the build. Has anybody experienced this as well?