As part of migration from Android to KMP, I need t...

# multiplatform

[Mark]

As part of migration from Android to KMP, I need to migrate the check (within a KMP library) for whether the current build is debug build (in Android, simply BuildConfig.DEBUG). I’ve tried BuildKonfig but that doesn’t provide a good solution for this either. Now I’m looking at creating an Android-only shared module (for this as well other things like resource ids not handled by KMP) and adding that as a dependency to androidMain of the KMP library. I would need to add solutions for other platforms, but am happy to defer that until later. Is that Android dependency-based strategy good or is there a better solution?

[zsmb]

If I understand your use case correctly, you could probably add an `expect`/`actual` function in your KMP module for this, and have the Android implementation return BuildConfig.DEBUG in androidMain.

[Mark]

I could only find a way for an Android-module to generate the BuildConfig . This is why I proposed the Android module dependency. Do you know of a way for KMP androidMain to be configured to build BuildConfig?

[zsmb]

A KMP library is an Android library if you have an Android target configured, so you can have a BuildConfig generated there.

I created this quick example, seems to work fine (implemented on Android, stubbed on iOS): https://github.com/zsmb13/BuildConfigExample250513/commit/6db2088c732bfe58ff5ffa83cda768def0d0da05

[Mark]

Interesting, thanks. I created the KMP module using the latest Android Studio New Module / Kotlin Multiplatform Shared Module, which adds the plugin: com.android.kotlin.multiplatform.library and this cannot be used with com.android.library in the same module. I guess this is why you are able to generate the BuildConfig. For the KMP android library plugin it allows configuration via kotlin { androidLibrary { … } } and it’s not clear to me how to convert that to the old Android way, or indeed whether I should go that route.

[zsmb]

Oh, I see, I'm not sure if there's equivalent config in the new plugin yet. I'll try to find out!

[Mark]

Is there documentation for migration from a KMP module using the com.android.library plugin to com.android.kotlin.multiplatform.library?
EDIT: https://developer.android.com/kotlin/multiplatform/plugin

[Mark]

Generally, the workaround of the KMP library module having a dependency on an Android-only module seems to be working. I use that Android-only module to store resources (for resource ids) as well as AndroidManifest (because I need to use addManifestPlaceholders which is unavailable in androidLibrary dsl). And for the BuildConfig as mentioned above. This is of course only a temporary solution as I continue to migrate the app to KMP. The one thing that isn’t working are unit tests that call code that reference resources. The tests (which are in androidHostTest) fail with: java.lang.NoClassDefFoundError: foo/bar/R$string

[zsmb]

Update: I got replies from the AGP folks, having a separate Android module with the AGP library plugin is really the way to do this with the new KMP Android plugin, as it doesn't offer variants (or a lot of other Android-specific features) on purpose.

[zsmb]

I don't have any context for the test issue - I suggest opening a new thread or filing an issue somewhere for that part

[Mark]

Thanks Márton. I wonder why they don’t want to support variants. This is very important for me, although not for the module I’m currently migrating. Is there an alternative approach they recommend across platforms?

[zsmb]

There's no built-in solution in KMP. We have an issue that tracks this request here that you can vote for / comment on with your use case: https://youtrack.jetbrains.com/issue/KT-33432/MPP-build-variant-feature