Unresolved reference for Java file in a different flavor when referencing from kotlin

Question

Problem:

This question has likely been answered implicitly from all the other similar questions but I can't seem to get it to work.

• If I reference a particular java file in another flavor (different source set) from a java file in the main source set it works.

• If I try to reference that same file from a Kotlin file in the main source set it complains that it can't see it ("Unresolved reference").

• If I move the same file to the main source set it works (so it's not the file itself).

• If I convert the Java file to Kotlin it works (and this is my current solution) but I'd like to know why it doesn't work since it's not always so easy to convert and it should work without converting.

Based on my Googling it seems it's related to the source sets in Gradle but I don't want a separate Kotlin folder alongside the Java folder so I'm not sure I need this. Also, another project where I have both Java and Kotlin doesn't have this configured and works fine.

I'm using productFlavors with flavorDimensions and have a source set called "dimension1Dimension2" (that's where the Java file I'm trying to reference is located).

Looking at my setup below, what am I possibly doing wrong or missing? This project is mostly Java so I'm just starting to add Kotlin to it. I can't see any differences with my other project that is mostly Kotlin and some Java.

One other thing that is weird is that it does work for one of the three flavors. There are two types of dimension1 and three types of dimension2. Just one of the dimension2 types works.

Maybe code is clearer:

flavorDimensions "product", "mode"    
productFlavors {
        mock { // only this one works (e.g. <company_name>Mock is the source set)
            applicationIdSuffix = ".mock"
            dimension "mode"
        }
        dev {
            applicationIdSuffix = ".dev"
            dimension "mode"
        }
        prod {
            dimension "mode"
        }
        demo {
            applicationIdSuffix = ".demo"
            dimension "product"
            buildConfigField "String", "UPDATE_DIRECTORY", "\"/release/\""
            buildConfigField "boolean", "SHOW_STREAM_STATUS", "false"
        }
        <company_name> {
            applicationIdSuffix = ".<company_name>"
            dimension "product"
        }
    }

---

Setup:

• Kotlin version: 1.2.21
• Gradle version: 3.0.1
• Plugins:
  • apply plugin: 'kotlin-android'
  • apply plugin: 'kotlin-kapt'
  • apply plugin: 'kotlin-android-extensions'
• Project level dependencies:
  • classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
• App level dependencies:
  • implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
• Using Java 8 in project settings

Answer 1

So I had the same issue and I couldn't just change everything on the fly to Kotlin as our app is a production app and we couldn't afford the time to change to Kotlin right away - the legacy code should stay Java for now at least.

I reported a bug to Google regarding this: https://issuetracker.google.com/issues/110100405

And lo and behold, a Google engineer actually answered my bug report quite fast :-)

If you don't want to read the conversation we had, I'll make it short:

TL;DR version:

The reason this doesn't work with Kotlin is because your packages are wrongly set up. I will bet you, that in some of your flavors you've done the same mistake as me and created directories like com.example.mypackage instead of creating the parent directory called com and then a sub-directory with the name example and then a sub-sub-directory called mypackage.

So if your folders look com.example.mypackage change them to com with sub-directories and all should be fine.

Another solution, which is probably the easiest is to create packages with the name com.example.mypackage in the different flavors, but this can only be done, when you've selected the flavor you want to create a package for.

As to why, this doesn't create issues with Java, I have no idea and the Google guy didn't either, but it's probably an IntelliJ issue, which I'll report to JetBrains unless they're already aware of it.

It's also a big issue that the Kotlin compiler just spits out a vague error saying Unresolved reference, but that's a talk for another day and another bug report or enhancement.