Android Variant Mapping

Variant mapping automatically generates environment-specific configuration for each Android build type or product flavor. This eliminates the need for -PactiveEnvironment flags or runtime environment selection on Android.

How It Works

1. You declare which build type maps to which environment
2. The plugin generates a flat EnvConfig object per variant
3. Each variant’s generated code is wired into its source set
4. At compile time, the correct environment values are baked in

Configuration

kenvConfig {
    directory.set(file("kenv"))
    environments.set(listOf("dev", "staging", "production"))
    generatedPackageName.set("com.example.config")

    variantMapping {
        buildType("debug") uses "dev"
        buildType("release") uses "production"
    }
}

Build Type Mapping

variantMapping {
    buildType("debug") uses "dev"
    buildType("release") uses "production"
}

Product Flavor Mapping

variantMapping {
    flavor("free") uses "dev"
    flavor("paid") uses "production"
}

Combined

variantMapping {
    buildType("debug") uses "dev"
    buildType("release") uses "production"
    flavor("staging") uses "staging"
}

Generated Output

With variant mapping, the generated code is a flat object — no nested environment objects:

// Generated for debug build type (using "dev" environment)
package com.example.config

object EnvConfig {
    val APP_VERSION: String = "2.0.0"
    val DEBUG_MODE: Boolean = true

    object Server {
        val API_BASE_URL: String = "http://localhost:8080"
        val API_PORT: Int = 8080
    }
}

Usage in Code

With variant mapping, access is straightforward:

// No environment prefix needed — values are resolved at compile time
val url = EnvConfig.Server.API_BASE_URL
val port = EnvConfig.Server.API_PORT
val debug = EnvConfig.DEBUG_MODE

The same code compiles differently for debug vs release builds, with each getting the correct environment values.

Source Set Wiring

For KMP Android projects, you may need to manually wire the generated source directory:

kotlin {
    sourceSets {
        androidMain {
            kotlin.srcDir(layout.buildDirectory.dir("generated/kenv/debug/kotlin"))
        }
    }
}

// Wire task dependencies
tasks.matching { it.name == "compileDebugKotlinAndroid" }.configureEach {
    dependsOn("kenvGenerateDebug")
}
tasks.matching { it.name == "compileReleaseKotlinAndroid" }.configureEach {
    dependsOn("kenvGenerateRelease")
}

Validation

The plugin validates that all mapped environments exist in the declared environments list:

// This will fail at configuration time:
kenvConfig {
    environments.set(listOf("dev", "production"))
    variantMapping {
        buildType("debug") uses "staging"  // Error: "staging" not in environments
    }
}

Error message:

Variant mapping error: build type 'debug' maps to environment 'staging'
which is not in declared environments: [dev, production]

When to Use Variant Mapping vs Runtime Selection

See Runtime Environment Selection for the KMP approach.