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Migrating to Convention Plugins

Zain Ul Hassan
7 min readJun 13, 2024

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Convention plugins apply conventions to a build. They do this by applying ecosystem plugins such as AGP and KGP, and then configuring those plugins according to the convention used by your build.

In this tutorial, you will learn how you can migrate your project to use convention plugins in small and detailed steps. So let’s get started.

Setting up build-logic project

  1. Start by creating the build-logic folder inside your root project.
  1. Create a file named settings.gradle.kts inside the build-logic directory and add following configuration:
dependencyResolutionManagement {
    // 1. Setup repositories to download dependencies
    repositories {
        google()
        mavenCentral()
    }
    
    // 2. Create version catalog named `libs` from 
    // the `libs.versions.toml` file already present in
    // the gradle folder.
    versionCatalogs {
        create("libs") {
            from(files("../gradle/libs.versions.toml"))
        }
    }
}

// 3. Set project name
rootProject.name = "build-logic"

// 4. Include the `convention` module that we will create next
include(":convention")

Here we have setup basic configuration for the build-logic project. This tutorial assumes that your project is using version catalog.

  1. Create a gradle.properties file and add the following properties:
org.gradle.parallel=true
org.gradle.caching=true
org.gradle.configureondemand=true
  1. Add build-logic as an included build in your <root>/settings.gradle.kts :
pluginManagement {
    // 1. Add build-logic as an includedBuild
    includeBuild("build-logic")
    
    repositories {
        google {
            content {
                includeGroupByRegex("com\\\\.android.*")
                includeGroupByRegex("com\\\\.google.*")
                includeGroupByRegex("androidx.*")
            }
        }
        mavenCentral()
        gradlePluginPortal()
    }
}

Setting up convention module

Start by creating a directory called convention in your build-logic directory:

Create a build.gradle.kts inside the convention directory and add basic configuration:

import org.jetbrains.kotlin.gradle.dsl.JvmTarget

plugins {
    `kotlin-dsl`
}

// Note: Replace with your package name
group = "org.dreamerslab.newslayer.buildlogic"

// Configure the build-logic plugins to target JDK 17
// This matches the JDK used to build the project, and is not related to what is running on device.
java {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

kotlin {
    compilerOptions {
        jvmTarget = JvmTarget.JVM_17
    }
}

tasks {
    validatePlugins {
        enableStricterValidation = true
        failOnWarning = true
    }
}

Next we will add plugins to the version catalog that are required by the build-logic . Add these plugins to gradle/libs.versions.toml file:

[versions]
# ...
agp = "8.4.2"
androidTools = "31.4.2"
kotlin = "2.0.0"

[libraries]
# ...

# Dependencies of the included build-logic
android-gradlePlugin = { group = "com.android.tools.build", name = "gradle", version.ref = "agp" }
android-tools-common = { group = "com.android.tools", name = "common", version.ref = "androidTools" }
compose-gradlePlugin = { module = "org.jetbrains.kotlin:compose-compiler-gradle-plugin", version.ref = "kotlin" }
kotlin-gradlePlugin = { group = "org.jetbrains.kotlin", name = "kotlin-gradle-plugin", version.ref = "kotlin" }

Now apply these plugins in your build-logic/convention/build.gradle.kts file:

import org.jetbrains.kotlin.gradle.dsl.JvmTarget

plugins {
    `kotlin-dsl`
}

// Note: Replace with your package name
group = "org.dreamerslab.newslayer.buildlogic"

// Configure the build-logic plugins to target JDK 17
// This matches the JDK used to build the project, and is not related to what is running on device.
java {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

kotlin {
    compilerOptions {
        jvmTarget = JvmTarget.JVM_17
    }
}

tasks {
    validatePlugins {
        enableStricterValidation = true
        failOnWarning = true
    }
}

// 1.Add plugins here
dependencies {
    compileOnly(libs.android.gradlePlugin)
    compileOnly(libs.android.tools.common)
    compileOnly(libs.compose.gradlePlugin)
    compileOnly(libs.kotlin.gradlePlugin)
}

Next create the source set directory inside convention module:

Creating configuration helper files

Let’s create the helper files that we will use to configure different plugins. We start by creating a file for project extensions:

ProjectExtensions.kt

package org.dreamerslab.newslayer

import org.gradle.api.Project
import org.gradle.api.artifacts.VersionCatalog
import org.gradle.api.artifacts.VersionCatalogsExtension
import org.gradle.kotlin.dsl.getByType

val Project.libs
    get(): VersionCatalog = extensions.getByType<VersionCatalogsExtension>().named("libs")

Versions.kt

package org.dreamerslab.newslayer

object Versions {
  const val COMPILE_SDK = 34
  const val MIN_SDK = 24
  const val TARGET_SDK = 34
}

KotlinAndroid.kt

package org.dreamerslab.newslayer

import com.android.build.api.dsl.CommonExtension
import org.gradle.api.JavaVersion
import org.gradle.api.Project
import org.gradle.api.plugins.JavaPluginExtension
import org.gradle.kotlin.dsl.assign
import org.gradle.kotlin.dsl.configure
import org.gradle.kotlin.dsl.provideDelegate
import org.jetbrains.kotlin.gradle.dsl.JvmTarget
import org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension
import org.jetbrains.kotlin.gradle.dsl.KotlinJvmProjectExtension
import org.jetbrains.kotlin.gradle.dsl.KotlinTopLevelExtension

/**
 * Configure base Kotlin with Android options
 */
internal fun Project.configureKotlinAndroid(
    commonExtension: CommonExtension<*, *, *, *, *, *>,
) {
    commonExtension.apply {
        compileSdk = Versions.COMPILE_SDK
        
        defaultConfig {
            minSdk = Versions.MIN_SDK
        }
        
        compileOptions {
            sourceCompatibility = JavaVersion.VERSION_11
            targetCompatibility = JavaVersion.VERSION_11
        }
    }

    configureKotlin<KotlinAndroidProjectExtension>()
}

/**
 * Configure base Kotlin options
 */
private inline fun <reified T : KotlinTopLevelExtension> Project.configureKotlin() = configure<T> {
    // Treat all Kotlin warnings as errors (disabled by default)
    // Override by setting warningsAsErrors=true in your ~/.gradle/gradle.properties
    val warningsAsErrors: String? by project

    when (this) {
        is KotlinAndroidProjectExtension -> compilerOptions
        is KotlinJvmProjectExtension -> compilerOptions
        else -> TODO("Unsupported project extension $this ${T::class}")
    }.apply {
        jvmTarget = JvmTarget.JVM_11
        allWarningsAsErrors = warningsAsErrors.toBoolean()
        freeCompilerArgs.add(
            // Enable experimental coroutines APIs, including Flow
            "-opt-in=kotlinx.coroutines.ExperimentalCoroutinesApi",
        )
    }
}

AndroidCompose.kt

package org.dreamerslab.newslayer

import com.android.build.api.dsl.CommonExtension
import org.gradle.api.Project
import org.gradle.kotlin.dsl.assign
import org.gradle.kotlin.dsl.configure
import org.gradle.kotlin.dsl.dependencies
import org.jetbrains.kotlin.compose.compiler.gradle.ComposeCompilerGradlePluginExtension

/**
 * Configure Compose-specific options
 */
internal fun Project.configureAndroidCompose(
    commonExtension: CommonExtension<*, *, *, *, *, *>,
) {
    commonExtension.apply {
        buildFeatures {
            compose = true
        }
        
        dependencies {
            val bom = libs.findLibrary("androidx-compose-bom").get()
            add("implementation", platform(bom))
            add("androidTestImplementation", platform(bom))
            add("implementation", libs.findLibrary("androidx-ui-tooling-preview").get())
            add("debugImplementation", libs.findLibrary("androidx-ui-tooling").get())
        }
    }

    extensions.configure<ComposeCompilerGradlePluginExtension> {
        enableStrongSkippingMode = true
    }
}

Creating plugins

We will create following necessary plugins:

AndroidApplicationConventionPlugin.kt

package org.dreamerslab.newslayer

import com.android.build.api.dsl.ApplicationExtensio
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.gradle.kotlin.dsl.configure

class AndroidApplicationConventionPlugin : Plugin<Project> {
    override fun apply(target: Project) {
        with(target) {
            with(pluginManager) {
                apply("com.android.application")
                apply("org.jetbrains.kotlin.android")
            }

            extensions.configure<ApplicationExtension> {
                configureKotlinAndroid(this)
                defaultConfig.targetSdk = Versions.TARGET_SDK
            }
        }
    }
}

AndroidApplicationComposeConventionPlugin.kt

package org.dreamerslab.newslayer

import com.android.build.api.dsl.ApplicationExtension
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.gradle.kotlin.dsl.apply
import org.gradle.kotlin.dsl.getByType

class AndroidApplicationComposeConventionPlugin : Plugin<Project> {
    override fun apply(target: Project) {
        with(target) {
            apply(plugin = "com.android.application")
            apply(plugin = "org.jetbrains.kotlin.plugin.compose")

            val extension = extensions.getByType<ApplicationExtension>()
            configureAndroidCompose(extension)
        }
    }
}

AndroidLibraryConventionPlugin.kt

package org.dreamerslab.newslayer

import com.android.build.gradle.LibraryExtension
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.gradle.kotlin.dsl.apply
import org.gradle.kotlin.dsl.configure

class AndroidLibraryConventionPlugin : Plugin<Project> {
    override fun apply(target: Project) {
        with(target) {
            with(pluginManager) {
                apply("com.android.library")
                apply("org.jetbrains.kotlin.android")
            }

            extensions.configure<LibraryExtension> {
                configureKotlinAndroid(this)
                defaultConfig.targetSdk = Versions.TARGET_SD
            }
        }
    }
}

AndroidLibraryComposeConventionPlugin.kt

package org.dreamerslab.newslayer

import com.android.build.gradle.LibraryExtension
import org.gradle.api.Plugin
import org.gradle.api.Project
import org.gradle.kotlin.dsl.apply
import org.gradle.kotlin.dsl.getByType

class AndroidLibraryComposeConventionPlugin : Plugin<Project> {
    override fun apply(target: Project) {
        with(target) {
            apply(plugin = "com.android.library")
            apply(plugin = "org.jetbrains.kotlin.plugin.compose")

            val extension = extensions.getByType<LibraryExtension>()
            configureAndroidCompose(extension)
        }
    }
}

Register plugins

Once you have created the plugins, you need to register them in build-logic/convention/build.gradle.kts :

import org.jetbrains.kotlin.gradle.dsl.JvmTarget

plugins {
    `kotlin-dsl`
}

group = "org.dreamerslab.newslayer.buildlogic"

// Configure the build-logic plugins to target JDK 17
// This matches the JDK used to build the project, and is not related to what is running on device.
java {
    sourceCompatibility = JavaVersion.VERSION_17
    targetCompatibility = JavaVersion.VERSION_17
}

kotlin {
    compilerOptions {
        jvmTarget = JvmTarget.JVM_17
    }
}

tasks {
    validatePlugins {
        enableStricterValidation = true
        failOnWarning = true
    }
}

dependencies {
    compileOnly(libs.android.gradlePlugin)
    compileOnly(libs.android.tools.common)
    compileOnly(libs.compose.gradlePlugin)
    compileOnly(libs.kotlin.gradlePlugin)
}

// 1. Register your plugins here
gradlePlugin {
    plugins {
        register("androidApplicationCompose") {
            id = "newslayer.android.application.compose"
            implementationClass = "org.dreamerslab.newslayer.AndroidApplicationComposeConventionPlugin"
        }
        register("androidApplication") {
            id = "newslayer.android.application"
            implementationClass = "org.dreamerslab.newslayer.AndroidApplicationConventionPlugin"
        }
        register("androidLibraryCompose") {
            id = "newslayer.android.library.compose"
            implementationClass = "org.dreamerslab.newslayer.AndroidLibraryComposeConventionPlugin"
        }
        register("androidLibrary") {
            id = "newslayer.android.library"
            implementationClass = "org.dreamerslab.newslayer.AndroidLibraryConventionPlugin"
        }
    }
}

When registering a plugin, we pass its name, a unique id and the implementationClass . We will later use the id to apply these plugins in our modules just like we apply an external plugin using its id.

Add custom plugins to version catalog

We can now add these plugins inside our gradle/libs.versions.toml file:

[plugins]
# ...

# Plugins defined by this project
newslayer-android-application = { id = "newslayer.android.application", version = "unspecified" }
newslayer-android-application-compose = { id = "newslayer.android.application.compose", version = "unspecified" }
newslayer-android-library = { id = "newslayer.android.library", version = "unspecified" }
newslayer-android-library-compose = { id = "newslayer.android.library.compose", version = "unspecified" }

Applying plugins in our project

We have successfully created custom plugins that we can now apply to our project modules. We will start by migrating the app module. Update the build gradle file as follows:

app/build.gradle.kts

plugins {
    // - alias(libs.plugins.android.application)
    // - alias(libs.plugins.jetbrains.kotlin.android)
    // - alias(libs.plugins.compose.compiler)
    
    // Apply custom plugins here
    alias(libs.plugins.newslayer.android.application)
    alias(libs.plugins.newslayer.android.application.compose)
}

android {
    namespace = "org.dreamerslab.newslayer"
    // - compileSdk = 34

    defaultConfig {
        applicationId = "org.dreamerslab.newslayer"
        // - minSdk = 24
        // - targetSdk = 34
        
        versionCode = 1
        versionName = "1.0"
        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
        vectorDrawables {
            useSupportLibrary = true
        }
    }
    buildTypes {
        release {
            isMinifyEnabled = true
            proguardFiles(
                getDefaultProguardFile("proguard-android-optimize.txt"),
                "proguard-rules.pro",
            )
        }
    }
    
    // - compileOptions {
    //     - sourceCompatibility = JavaVersion.VERSION_17
    //     - targetCompatibility = JavaVersion.VERSION_17
    // }
    // - kotlin {
    //     - jvmToolchain(17)
    // }
    // - buildFeatures {
    //     - compose = true
    // }

    packaging {
        resources {
            excludes += "/META-INF/{AL2.0,LGPL2.1}"
        }
    }
}
dependencies {
    // ...
  
    // - implementation(platform(libs.androidx.compose.bom))
    // - implementation(libs.androidx.ui.tooling.preview)
    // - androidTestImplementation(platform(libs.androidx.compose.bom))
    // - debugImplementation(libs.androidx.ui.tooling)
}

We will also apply custom plugins to out android modules that use compose. I’ll apply it to the. :common:ui module.

common/ui/build.gradle.kts

plugins {
    // - alias(libs.plugins.android.library)
    // - alias(libs.plugins.jetbrains.kotlin.android)
    // - alias(libs.plugins.compose.compiler)

    // Apply plugins
    alias(libs.plugins.newslayer.android.library)
    alias(libs.plugins.newslayer.android.library.compose)
}

android {
    namespace = "org.dreamerslab.newslayer.ui"
    // - compileSdk = 34
    defaultConfig {
        // - minSdk = 24

        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
        consumerProguardFiles("consumer-rules.pro")
    }
    
    // - compileOptions {
    //     - sourceCompatibility = JavaVersion.VERSION_17
    //     - targetCompatibility = JavaVersion.VERSION_17
    // }
    // - kotlin {
    //     - jvmToolchain(17)
    // }
    // - buildFeatures {
    //     - compose = true
    // }
}

dependencies {
    // ...
  
    // - implementation(platform(libs.androidx.compose.bom))
    // - implementation(libs.androidx.ui.tooling.preview)
    // - androidTestImplementation(platform(libs.androidx.compose.bom))
    // - debugImplementation(libs.androidx.ui.tooling)
}

By following this approach, you can update your sub-modules to use build-logic plugins.

Enable caching for faster builds

Add following properties to your <root>/gradle.properties to enable caching for faster builds:

# Enable caching between builds.
org.gradle.caching=true

# Enable configuration caching between builds.
org.gradle.configuration-cache=true

Useful Resources

Kotlin
Gradle
Android
Gradle Kotlin Dsl
Compose

--

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Zain Ul Hassan

Written by Zain Ul Hassan

8 Followers

Mobile App Developer | Android | Kotlin, Compose, Flutter, and Dart

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