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Declarative Gradle for Android#

1. Summary#

Declarative Gradle DSL is currently in alpha.

The Declarative Gradle DSL code is available at https://github.com/gradle/declarative-gradle/tree/main/unified-prototype. The Declarative Gradle DSL plugin for Android is available at: https://plugins.gradle.org/plugin/org.gradle.experimental.android-library. You can find a list of all available plugins here

Common build files written using the Groovy DSL or Kotlin DSL with the name build.gradle and build.gradle.kts respectively will be replaced with build.gradle.dcl.

.dcl files are written in Kotlin in a fully declarative way.

2. Key features / Syntax examples#

The restricted DSL allows a limited set of constructs. Generic control flow and calls to arbitrary methods are not allowed.

For Android, the androidLibrary and androidApplication software types are used. For other applications, there are jvmLibrary and kmpLibrary types available as well. Therefore, your build.gradle.dcl files begin with:

androidLibrary {
}

The androidLibrary software type exposes several configuration options and dependencies. 

androidLibrary {
    namespace = ""
    dependencies {}
    buildTypes {}
}

As you can see, there is no imperative logic here.

The androidApplication software type can be found here.

3. Getting Started with NowInAndroid#

Now in Android is a fully functional Android app built entirely with Kotlin and Jetpack Compose from the Android team.

We forked Now in Android and updated the build files using the Declarative Gradle DSL. The prototype repository can be found here.

The settings file applies a new "Android ecosystem plugin", which exposes androidLibrary and androidApplication software types that can be used in subprojects.

The current prototype is limited to a single androidLibrary software type convention, so only a few subprojects have been converted.

Converted subprojects: - :core:common - :core:data - :core:domain

Let’s take a look at a build.gradle.dcl file which replaces the common build.gradle or build.gradle.kts files:

core/common/build.gradle.dcl

androidLibrary {
    namespace = "com.google.samples.apps.nowinandroid.core.common"
    dependencies {
        testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.3")
        testImplementation("app.cash.turbine:turbine:1.0.0")
    }
    buildTypes {
        buildTypes {
            // Need the empty closure to avoid "dangling pure expression" error
            debug {}
            release {}
        }
    }
}

The androidLibrary software type exposes several configuration options and dependencies.

3.1 Prerequisites#

3.2 Setup#

git clone https://github.com/gradle/nowinandroid.git
cd nowinandroid
git checkout main-declarative
git clone https://github.com/gradle/declarative-gradle.git

This should checkout the main branch of the Declarative Gradle prototype plugins inside the root of Gradle's NowInAndroid fork.

You should have this project structure: 

nowinandroid/
    declarative-gradle/

3.3 Building#

You can assemble the project with the following command:

./gradlew buildDemoDebug

3.4 Testing#

You can run tests using the following commands:

./gradlew testDemoDebug :lint:test

./gradlew testDemoDebugUnitTest -Proborazzi.test.verify=false

After starting a local Android emulator in Android Studio: ```shell ./gradlew connectedDemoDebugAndroidTest --daemon ````