BuildKonfig

BuildConfig for Kotlin Multiplatform Project.
It currently supports embedding values from gradle file.

Table Of Contents

• Motivation
• Usage
  • Requirements
  • Gradle Configuration
  • Product Flavor?
  • Overwriting Values
  • HMPP
• Supported Types
• Try out the sample

<a name="motivation"/>

Motivation

Passing values from Android/iOS or any other platform code should work, but it's a hassle.
Setting up Android to read values from properties and add those into BuildConfig, and do the equivalent in iOS?
Rather I'd like to do it once.

<a name="usage"/>

Usage

<a name="requirements"/>

Requirements

• Kotlin 1.5.30 or later
• Kotlin Multiplatform Project
• Gradle 7 or later

<a name="gradle-configuration"/>

Gradle Configuration

Simple configuration

<details open> <summary>Kotlin DSL</summary>

import com.codingfeline.buildkonfig.compiler.FieldSpec.Type.STRING

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.21")
        classpath("com.codingfeline.buildkonfig:buildkonfig-gradle-plugin:latest_version")
    }
}

plugins {
    kotlin("multiplatform")
    id("com.codingfeline.buildkonfig")
}

kotlin {
    // your target config...
    androidTarget()
    iosX64('ios')
}

buildkonfig {
    packageName = "com.example.app"
    // objectName = "YourAwesomeConfig"
    // exposeObjectWithName = "YourAwesomePublicConfig"

    defaultConfigs {
        buildConfigField(STRING, "name", "value")
    }
}

</details> <details> <summary>Groovy DSL</summary>

buildScript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.21'
        classpath 'com.codingfeline.buildkonfig:buildkonfig-gradle-plugin:latest_version'
    }
}

apply plugin: 'org.jetbrains.kotlin.multiplatform'
apply plugin: 'com.codingfeline.buildkonfig'

kotlin {
    // your target config...
    androidTarget()
    iosX64('ios')
}

buildkonfig {
    packageName = 'com.example.app'
    // objectName = 'YourAwesomeConfig'
    // exposeObjectWithName = 'YourAwesomePublicConfig'

    defaultConfigs {
        buildConfigField 'STRING', 'name', 'value'
    }
}

</details>

• packageName Set the package name where BuildKonfig is being placed. Required.
• objectName Set the name of the generated object. Defaults to BuildKonfig.
• exposeObjectWithName Set the name of the generated object, and make it public.
• defaultConfigs Set values which you want to have in common. Required.

To generate BuildKonfig files, run generateBuildKonfig task.
This task will be automatically run upon execution of kotlin compile tasks.

Above configuration will generate following simple object.

// commonMain
package com.example.app

internal object BuildKonfig {
    val name: String = "value"
}

Configuring target dependent values

If you want to change value depending on your targets, you can use targetConfigs to define target-dependent values.

<details open> <summary>Kotlin DSL</summary>

import com.codingfeline.buildkonfig.compiler.FieldSpec.Type.STRING

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.21")
        classpath("com.codingfeline.buildkonfig:buildkonfig-gradle-plugin:latest_version")
    }
}

plugins {
    kotlin("multiplatform")
    id("com.codingfeline.buildkonfig")
}

kotlin {
    // your target config...
    androidTarget()
    iosX64('ios')
}

buildkonfig {
    packageName = "com.example.app"

    // default config is required
    defaultConfigs {
        buildConfigField(STRING, "name", "value")
    }

    targetConfigs {
        // names in create should be the same as target names you specified
        create("android") {
            buildConfigField(STRING, "name2", "value2")
            buildConfigField(STRING, "nullableField", "NonNull-value", nullable = true)
        }

        create("ios") {
            buildConfigField(STRING, "name", "valueForNative")
        }
    }
}

</details> <details> <summary>Groovy DSL</summary>

buildScript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:2.1.21'
        classpath 'com.codingfeline.buildkonfig:buildkonfig-gradle-plugin:latest_version'
    }
}

apply plugin: 'org.jetbrains.kotlin.multiplatform'
apply plugin: 'com.codingfeline.buildkonfig'

kotlin {
    // your target config...
    androidTarget()
    iosX64('ios')
}

buildkonfig {
    packageName = 'com.example.app'

    // default config is required
    defaultConfigs {
        buildConfigField 'STRING', 'name', 'value'
        buildConfigField 'STRING', 'nullableField', null, nullable: true
    }

    targetConfigs {
        // this name should be the same as target names you specified
        android {
            buildConfigField 'STRING', 'name2', 'value2'
            buildConfigField 'STRING', 'nullableField', 'NonNull-value', nullable: true
        }

        ios {
            buildConfigField 'STRING', 'name', 'valueForNative'
        }
    }
}

</details>

• packageName
  • Sets the package name where BuildKonfig is being placed. Required.
• objectName
  • Sets the name of the generated object. Defaults to BuildKonfig.
• exposeObjectWithName
  • Sets the name of the generated object, and make it public.
• defaultConfigs
  • Sets values which you want to have in common. Required.
• targetConfigs
  • Sets target specific values as closure. You can overwrite values specified in defaultConfigs.
• buildConfigField(type: String, name: String, value: String)
  • Adds new value or overwrite existing one.
• buildConfigField(type: String, name: String, value: String, nullable: Boolean = false, const: Boolean = false)
  • In addition to above method, this can configure nullable and const declarations.

Above configuration will generate following codes.

// commonMain
package com.example.app

internal expect object BuildKonfig {
    val name: String
    val nullableField: String?
}

// androidMain
package com.example.app

internal actual object BuildKonfig {
    actual val name: String = "value"
    actual val nullableField: String? = "NonNull-value"
    val name2: String = "value2"
}

// iosMain
package com.example.app

internal actual object BuildKonfig {
    actual val name: String = "valueForNative"
    actual val nullableField: String? = null
}

<a name="product-flavor"/>

Product Flavor?

Yes(sort of).
Kotlin Multiplatform Project does not support product flavor. Kotlin/Native part of the project has release/debug distinction, but it's not global.
So to mimick product flavor capability of Android, we need to provide additional property in order to determine flavors.

Specify default flavor in your gradle.properties

# ROOT_DIR/gradle.properties
buildkonfig.flavor=dev

<details open> <summary>Kotlin DSL</summary>

import com.codingfeline.buildkonfig.compiler.FieldSpec.Type.STRING
import com.codingfeline.buildkonfig.gradle.TargetConfigDsl

buildkonfig {
    packageName = "com.example.app"

    // default config is required
    defaultConfigs {
        buildConfigField(STRING, "name", "value")
    }
    // flavor is passed as a first argument of defaultConfigs
    defaultConfigs("dev") {
        buildConfigField(STRING, "name", "devValue")
    }

    targetConfigs {
        create("android") {
            buildConfigField(STRING, "name2", "value2")
        }

        create("ios") {
            buildConfigField(STRING, "name", "valueIos")
        }
    }
    // flavor is passed as a first argument of targetConfigs
    targetConfigs("dev") {
        create("ios") {
            buildConfigField(STRING, "name", "devValueIos")
        }
    }
}

</details> <details> <summary>Groovy DSL</summary>

// ./mpp_project/build.gradle

buildkonfig {
    packageName = 'com.example.app'

    // default config is required
    defaultConfigs {
        buildConfigField 'STRING', 'name', 'value'
    }
    // flavor is passed as a first argument of defaultConfigs
    defaultConfigs("dev") {
        buildConfigField 'STRING', 'name', 'devValue'
    }

    targetConfigs {
        android {
            buildConfigField 'STRING', 'name2', 'value2'
        }

        ios {
            buildConfigField 'STRING', 'name', 'valueIos'
        }
    }
    // flavor is passed as a first argument of targetConfigs
    targetConfigs("dev") {
        ios {
            buildConfigField 'STRING', 'name', 'devValueIos'
        }
    }
}

</details>

In a development phase you can change value in gradle.properties as you like.
In CI environment, you can pass value via CLI $ ./gradlew build -Pbuildkonfig.flavor=release

<a name="overwriting-values"/>

Overwriting Values

If you configure same field across multiple defaultConfigs and targetConfigs, flavored targetConfigs is the strongest.

Lefter the stronger.

Flavored TargetConfig > TargetConfig > Flavored DefaultConfig > DefaultConfig

<a name="hmpp"/>

HMPP Support

a.k.a Intermediate SourceSets. (see Share code on platforms for detail.)
BuildKonfig supports HMPP. However there's some limitations.

**When you add a targetConfigs