Support `com.android.kotlin.multiplatform.library`

[vRallev]

The new Gradle plugin com.android.kotlin.multiplatform.library to configure Android in KMP projects isn't supported by KSP yet. This blocks the migration to the new plugin.

My project is building fine for with the current setup, e.g. I'm adding a KSP dependency like this:

dependencies {
    kspAndroid libs.kotlin.inject.ksp
}

However, when migrating to the new plugin the exact same line triggers dependency resolution errors:

Error

Could not determine the dependencies of task ':presenter-molecule:impl:kspAndroidMain'.
> Could not resolve all dependencies for configuration ':presenter-molecule:impl:androidCompileClasspath'.
   > The consumer was configured to find a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'androidJvm'. However we cannot choose between the following variants of project :presenter-molecule:public:
       - Configuration ':presenter-molecule:public:androidApiElements' variant android-classes-jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-classes-jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter-molecule:public:androidApiElements' variant android-lint declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter-molecule:public:androidApiElements' variant android-lint-local-aar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint-local-aar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter-molecule:public:androidApiElements' variant android-manifest declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-manifest' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter-molecule:public:androidApiElements' variant jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
   > The consumer was configured to find a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'androidJvm'. However we cannot choose between the following variants of project :kotlin-inject:public:
       - Configuration ':kotlin-inject:public:androidApiElements' variant android-classes-jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-classes-jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject:public:androidApiElements' variant android-lint declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject:public:androidApiElements' variant android-lint-local-aar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint-local-aar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject:public:androidApiElements' variant android-manifest declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-manifest' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject:public:androidApiElements' variant jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
   > The consumer was configured to find a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'androidJvm'. However we cannot choose between the following variants of project :kotlin-inject-extensions:contribute:public:
       - Configuration ':kotlin-inject-extensions:contribute:public:androidApiElements' variant android-classes-jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-classes-jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject-extensions:contribute:public:androidApiElements' variant android-lint declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject-extensions:contribute:public:androidApiElements' variant android-lint-local-aar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint-local-aar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject-extensions:contribute:public:androidApiElements' variant android-manifest declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-manifest' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':kotlin-inject-extensions:contribute:public:androidApiElements' variant jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
   > The consumer was configured to find a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'androidJvm'. However we cannot choose between the following variants of project :scope:public:
       - Configuration ':scope:public:androidApiElements' variant android-classes-jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-classes-jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':scope:public:androidApiElements' variant android-lint declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':scope:public:androidApiElements' variant android-lint-local-aar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint-local-aar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':scope:public:androidApiElements' variant android-manifest declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-manifest' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':scope:public:androidApiElements' variant jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
   > The consumer was configured to find a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'androidJvm'. However we cannot choose between the following variants of project :presenter:public:
       - Configuration ':presenter:public:androidApiElements' variant android-classes-jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-classes-jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter:public:androidApiElements' variant android-lint declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter:public:androidApiElements' variant android-lint-local-aar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-lint-local-aar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter:public:androidApiElements' variant android-manifest declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'android-manifest' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it
       - Configuration ':presenter:public:androidApiElements' variant jar declares a library for use during compile-time, preferably optimized for Android, as well as attribute 'com.android.build.api.attributes.AgpVersionAttr' with value '8.10.1', attribute 'org.jetbrains.kotlin.platform.type' with value 'jvm':
           - Unmatched attributes:
               - Provides attribute 'artifactType' with value 'jar' but the consumer didn't ask for it
               - Provides its elements packaged as a jar but the consumer didn't ask for it

[MichalDanielDobrzanski]

Any updates on this?

[Nek-12]

Our project no longer builds with AGP 9.0, the old plugin is terminally deprecated, and on 8.x it issues 60+ deprecation warnings. Should we remove ksp from our codebase?

[hfmehmed]

You should still be able to use

                project.dependencies.add("kspAndroid", <your-processor>)

with the new android kmp plugin.

The reported problem is interesting. I can't tell if its directly related to KSP or something to do with gradle resolution. Do you have a reproducing project for it? Does it still happen with latest android kmp plugin versions?

[kingg22]

You should still be able to use
with the new android kmp plugin.

Hey @hfmehmed Thanks u sm for the reply, yes, now I can use KSP with Android KMP library plugin, but kspCommonMainMetadata now is not available, this break my compiler and probably many others
For example: The new kotlinx-schema processor
Ktorfit with gradle plugin, etc
See Slack - KSP thread and #1021

Just to be clear, will this now be the default behavior of ksp?

[kingg22]

I'm having this issue after ksp runs, but I'm not sure is android KMP library or ksp invalid kotlin src or other origin.
Extending sealed classes or interfaces from a different module is prohibited.
Before using android library and ksp only on kspCommonMainMetadata works fine

[consp1racy]

I managed to get a working Dagger/KSP setup.

Kotlin 2.3.0, AGP 9.0.0-rc01, KSP 2.3.4, Dagger 2.57.2

plugins {
    id("org.jetbrains.kotlin.multiplatform")
    id("com.android.kotlin.multiplatform.library")
    id("com.google.devtools.ksp")
}

kotlin {
    androidLibrary {
        namespace = // ...

        withJava()
    }

    sourceSets {
        androidMain {
            dependencies {
                implementation(libs.dagger.core)
            }
        }
    }
}

dependencies {
    add("kspAndroid", libs.dagger.compiler)
}

See also

• https://developer.android.com/kotlin/multiplatform/plugin#enable-java
• https://kotlinlang.org/docs/multiplatform/multiplatform-compatibility-guide.html#java-source-sets-created-by-default

Problem

This happens:

> Task :extra:settings:api:kspAndroidMain FAILED
[Incubating] Problems report is available at: file:///C:/Users/.../build/reports/problems/problems-report.html
FAILURE: Build failed with an exception.
* What went wrong:
A problem was found with the configuration of task ':extra:settings:api:kspAndroidMain' (type 'KspAATask').
- Gradle detected a problem with the following location: 'C:\Users\...\extra\settings\api\build\generated\ksp\android\androidMain\java'.

Reason: Task ':extra:settings:api:extractAndroidMainAnnotations' uses this output of task ':extra:settings:api:kspAndroidMain' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.

Possible solutions:
1. Declare task ':extra:settings:api:kspAndroidMain' as an input of ':extra:settings:api:extractAndroidMainAnnotations'.
2. Declare an explicit dependency on ':extra:settings:api:kspAndroidMain' from ':extra:settings:api:extractAndroidMainAnnotations' using Task#dependsOn.
3. Declare an explicit dependency on ':extra:settings:api:kspAndroidMain' from ':extra:settings:api:extractAndroidMainAnnotations' using Task#mustRunAfter.

For more information, please refer to https://docs.gradle.org/9.2.1/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.

[realdadfish]

Reason: Task ':extra:settings:api:extractAndroidMainAnnotations' uses this output of task ':extra:settings:api:kspAndroidMain' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.

This can be easily fixed by

tasks.named { it == "kspAndroidMain" }.configureEach {
    dependsOn(tasks.named("extractAndroidMainAnnotations"))
}

until this issue is resolved.

[jyseolois]

Still not resolved yet?

[chrisbanes]

We kept seeing KSP not working up generation for Android source sets. Ended up with this workaround:

/**
 * Workaround for KSP not wiring kspAndroidMainProcessorClasspath to extend from kspAndroid
 * when using the com.android.kotlin.multiplatform.library plugin (AGP 9).
 *
 * See: https://github.com/google/ksp/issues/2476
 */
private fun Project.fixKspAndroidMainProcessorClasspath() {
    val kspAndroid = configurations.findByName("kspAndroid") ?: return
    val processorClasspath = configurations.findByName("kspAndroidMainProcessorClasspath")
    if (processorClasspath != null) {
        // Configuration already exists, wire it up
        if (kspAndroid !in processorClasspath.extendsFrom) {
            processorClasspath.extendsFrom(kspAndroid)
        }
    } else {
        // Configuration doesn't exist yet (created lazily by KSP), wire it up when it appears
        configurations.configureEach {
            if (name == "kspAndroidMainProcessorClasspath" && kspAndroid !in extendsFrom) {
                extendsFrom(kspAndroid)
            }
        }
    }
}