Duplicate files copied in APK META-INF/library_release.kotlin_module

After looking at other conflicts, it seems like the resolution is

packagingOptions {
    pickFirst 'META-INF/library_release.kotlin_module'
}

under android in the app gradle.

This allows the apk to build

You should add this to the build.gradle file of your app inside the android tag

packagingOptions {
    exclude 'META-INF/library_release.kotlin_module'
}

As suggested in the post Kotlin M13 is out! by jetbrains:

Make sure these .kotlin_module files are not stripped by your packaging process.

So, we can't use exclude option to exclude this resource file from being generated.

As descripted in Kotlin M13 is out!, we should:

in Maven we use groupId and artifactId for module names, but you can say

<configuration>
    <moduleName>com.example.mymodule</moduleName>
</configuration>

in Gradle it’s project name + build task name, to customize:

compileKotlin {
    kotlinOptions.moduleName = "com.example.mymodule"    
}

This is my configuration for Android library project:

ext {
    GROUP_ID = 'custom.group.id'
    ARTIFACT_ID = 'artifactid'
}

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"

    compileOptions {
        kotlinOptions.freeCompilerArgs += ['-module-name', "$GROUP_ID.$ARTIFACT_ID"]
    }

    defaultConfig {
        ...
    }
    buildTypes {
        ...
    }
}

Resource file named META-INF/custom.group.id.artifactId.kotlin_module will be generated instead of META-INF/library_release.kotlin_module.No more duplicate files will be found.

You can read this post and this post for more information.