DID-10137: [FIX-FLUTTER-KGP] Android: support AGP 9 built-in Kotlin (apply KGP only when built-in Kotlin is off)

.github/workflows/ci.yml

@@ -85,12 +85,85 @@ jobs:
           flutter pub get
           flutter build apk --debug
 
+      # The example's MainActivity is Kotlin. A build that skipped Kotlin
+      # compilation still packages an APK, so check the class is in it.
+      - name: Example APK contains the Kotlin MainActivity
+        working-directory: example
+        run: |
+          apk=build/app/outputs/flutter-apk/app-debug.apk
+          if ! unzip -p "$apk" 'classes*.dex' | grep -aq 'Lme/didit/sdk/sdk_flutter_example/MainActivity;'; then
+            echo "::error::$apk has no MainActivity class: the example's Kotlin sources were not compiled"
+            exit 1
+          fi
+
       # The plugin's JVM unit tests (android/src/test) against the released
       # native AAR, inside the Gradle project the build above generated.
       - name: Plugin unit tests (Android)
         working-directory: example/android
         run: ./gradlew :didit_sdk:testDebugUnitTest
 
+  build-android-example-agp9:
+    name: Example app builds (Android, AGP 9 built-in Kotlin)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          cache: true
+
+      # The example stays on AGP 8 in the repository (the job above); this run
+      # moves it to AGP 9 with built-in Kotlin, which refuses any project that
+      # also applies the Kotlin Gradle Plugin (KGP). Setting the flag explicitly
+      # also stops Flutter from writing android.builtInKotlin=false.
+      - name: Move the example to AGP 9 with built-in Kotlin
+        working-directory: example/android
+        run: |
+          sed -i 's/id("com.android.application") version "[^"]*"/id("com.android.application") version "9.2.1"/' settings.gradle.kts
+          sed -i 's/gradle-[0-9.]*-all\.zip/gradle-9.5.1-all.zip/' gradle/wrapper/gradle-wrapper.properties
+          printf '\nandroid.builtInKotlin=true\nandroid.newDsl=false\n' >> gradle.properties
+          grep -q 'id("com.android.application") version "9.2.1"' settings.gradle.kts
+          grep -q 'gradle-9.5.1-all.zip' gradle/wrapper/gradle-wrapper.properties
+
+      - name: Build example APK
+        working-directory: example
+        run: |
+          flutter pub get
+          flutter build apk --debug 2>&1 | tee "$RUNNER_TEMP/build-apk.log"
+
+      # Built-in Kotlin must compile the example's Kotlin MainActivity too.
+      - name: Example APK contains the Kotlin MainActivity
+        working-directory: example
+        run: |
+          apk=build/app/outputs/flutter-apk/app-debug.apk
+          if ! unzip -p "$apk" 'classes*.dex' | grep -aq 'Lme/didit/sdk/sdk_flutter_example/MainActivity;'; then
+            echo "::error::$apk has no MainActivity class: the example's Kotlin sources were not compiled"
+            exit 1
+          fi
+
+      - name: Plugin unit tests (Android)
+        working-directory: example/android
+        run: ./gradlew :didit_sdk:testDebugUnitTest 2>&1 | tee "$RUNNER_TEMP/unit-tests.log"
+
+      # Flutter names every plugin that still applies KGP and will refuse to
+      # build them in a future release.
+      - name: No KGP warning names didit_sdk
+        run: |
+          if grep -h 'plugins that apply Kotlin Gradle Plugin (KGP):.*didit_sdk' "$RUNNER_TEMP/build-apk.log" "$RUNNER_TEMP/unit-tests.log"; then
+            echo "::error::Flutter reports that didit_sdk applies the Kotlin Gradle Plugin on AGP 9"
+            exit 1
+          fi
+
   build-ios-example:
     name: Example app builds (iOS)
     runs-on: macos-latest

android/build.gradle.kts

@@ -56,7 +56,16 @@ rootProject.allprojects {
 
 plugins {
     id("com.android.library")
-    id("kotlin-android")
+}
+
+// AGP 9+ compiles Kotlin itself ("built-in Kotlin") and rejects the Kotlin
+// Gradle Plugin, and Flutter warns about plugins that declare it. Apply KGP only
+// where built-in Kotlin is off: AGP 8, or AGP 9 with android.builtInKotlin=false
+// (the same rule Flutter's Gradle plugin uses).
+val builtInKotlin = androidComponents.pluginVersion.major >= 9 &&
+    (providers.gradleProperty("android.builtInKotlin").orNull?.toBoolean() ?: true)
+if (!builtInKotlin) {
+    apply(plugin = "kotlin-android")
 }
 
 android {
@@ -69,10 +78,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
     sourceSets {
         getByName("main") {
             java.srcDirs("src/main/kotlin")
@@ -107,12 +112,22 @@ android {
     }
 }
 
+// The `kotlin` extension exists with both KGP and built-in Kotlin, unlike
+// android.kotlinOptions, which only KGP adds.
+extensions.configure<org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension>("kotlin") {
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
+    }
+}
+
 dependencies {
     implementation("me.didit:$diditSdkAndroidArtifact:$diditSdkAndroidVersion")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
 
-    testImplementation("org.jetbrains.kotlin:kotlin-test")
+    // KGP infers the JUnit 5 flavour of kotlin-test; built-in Kotlin does not.
+    testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("io.mockk:mockk:1.14.11")
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.8.1")
 }

example/android/app/build.gradle.kts

@@ -1,7 +1,9 @@
 plugins {
     id("com.android.application")
-    id("kotlin-android")
-    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
+    // No Kotlin Gradle Plugin here: on AGP 9 built-in Kotlin compiles src/main/kotlin, and on
+    // AGP 8 the Flutter Gradle Plugin applies the Kotlin Gradle Plugin itself (the `kotlin { }`
+    // block below would not resolve otherwise). CI checks the APK contains MainActivity on both.
+    // The Flutter Gradle Plugin must be applied after the Android Gradle Plugin.
     id("dev.flutter.flutter-gradle-plugin")
 }
 
@@ -15,10 +17,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
     defaultConfig {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId = "me.didit.sdk.sdk_flutter_example"
@@ -45,6 +43,12 @@ android {
     }
 }
 
+kotlin {
+    compilerOptions {
+        jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
+    }
+}
+
 flutter {
     source = "../.."
 }

packages/didit_sdk_autodetection/android/build.gradle.kts

@@ -56,7 +56,16 @@ rootProject.allprojects {
 
 plugins {
     id("com.android.library")
-    id("kotlin-android")
+}
+
+// AGP 9+ compiles Kotlin itself ("built-in Kotlin") and rejects the Kotlin
+// Gradle Plugin, and Flutter warns about plugins that declare it. Apply KGP only
+// where built-in Kotlin is off: AGP 8, or AGP 9 with android.builtInKotlin=false
+// (the same rule Flutter's Gradle plugin uses).
+val builtInKotlin = androidComponents.pluginVersion.major >= 9 &&
+    (providers.gradleProperty("android.builtInKotlin").orNull?.toBoolean() ?: true)
+if (!builtInKotlin) {
+    apply(plugin = "kotlin-android")
 }
 
 android {
@@ -69,10 +78,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
     sourceSets {
         getByName("main") {
             java.srcDirs("src/main/kotlin")
@@ -107,12 +112,22 @@ android {
     }
 }
 
+// The `kotlin` extension exists with both KGP and built-in Kotlin, unlike
+// android.kotlinOptions, which only KGP adds.
+extensions.configure<org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension>("kotlin") {
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
+    }
+}
+
 dependencies {
     implementation("me.didit:$diditSdkAndroidArtifact:$diditSdkAndroidVersion")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
 
-    testImplementation("org.jetbrains.kotlin:kotlin-test")
+    // KGP infers the JUnit 5 flavour of kotlin-test; built-in Kotlin does not.
+    testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("io.mockk:mockk:1.14.11")
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.8.1")
 }

packages/didit_sdk_core/android/build.gradle.kts

@@ -56,7 +56,16 @@ rootProject.allprojects {
 
 plugins {
     id("com.android.library")
-    id("kotlin-android")
+}
+
+// AGP 9+ compiles Kotlin itself ("built-in Kotlin") and rejects the Kotlin
+// Gradle Plugin, and Flutter warns about plugins that declare it. Apply KGP only
+// where built-in Kotlin is off: AGP 8, or AGP 9 with android.builtInKotlin=false
+// (the same rule Flutter's Gradle plugin uses).
+val builtInKotlin = androidComponents.pluginVersion.major >= 9 &&
+    (providers.gradleProperty("android.builtInKotlin").orNull?.toBoolean() ?: true)
+if (!builtInKotlin) {
+    apply(plugin = "kotlin-android")
 }
 
 android {
@@ -69,10 +78,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
     sourceSets {
         getByName("main") {
             java.srcDirs("src/main/kotlin")
@@ -107,12 +112,22 @@ android {
     }
 }
 
+// The `kotlin` extension exists with both KGP and built-in Kotlin, unlike
+// android.kotlinOptions, which only KGP adds.
+extensions.configure<org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension>("kotlin") {
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
+    }
+}
+
 dependencies {
     implementation("me.didit:$diditSdkAndroidArtifact:$diditSdkAndroidVersion")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
 
-    testImplementation("org.jetbrains.kotlin:kotlin-test")
+    // KGP infers the JUnit 5 flavour of kotlin-test; built-in Kotlin does not.
+    testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("io.mockk:mockk:1.14.11")
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.8.1")
 }

packages/didit_sdk_nfc/android/build.gradle.kts

@@ -56,7 +56,16 @@ rootProject.allprojects {
 
 plugins {
     id("com.android.library")
-    id("kotlin-android")
+}
+
+// AGP 9+ compiles Kotlin itself ("built-in Kotlin") and rejects the Kotlin
+// Gradle Plugin, and Flutter warns about plugins that declare it. Apply KGP only
+// where built-in Kotlin is off: AGP 8, or AGP 9 with android.builtInKotlin=false
+// (the same rule Flutter's Gradle plugin uses).
+val builtInKotlin = androidComponents.pluginVersion.major >= 9 &&
+    (providers.gradleProperty("android.builtInKotlin").orNull?.toBoolean() ?: true)
+if (!builtInKotlin) {
+    apply(plugin = "kotlin-android")
 }
 
 android {
@@ -69,10 +78,6 @@ android {
         targetCompatibility = JavaVersion.VERSION_17
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
     sourceSets {
         getByName("main") {
             java.srcDirs("src/main/kotlin")
@@ -107,12 +112,22 @@ android {
     }
 }
 
+// The `kotlin` extension exists with both KGP and built-in Kotlin, unlike
+// android.kotlinOptions, which only KGP adds.
+extensions.configure<org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension>("kotlin") {
+    compilerOptions {
+        jvmTarget.set(org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17)
+    }
+}
+
 dependencies {
     implementation("me.didit:$diditSdkAndroidArtifact:$diditSdkAndroidVersion")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3")
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
 
-    testImplementation("org.jetbrains.kotlin:kotlin-test")
+    // KGP infers the JUnit 5 flavour of kotlin-test; built-in Kotlin does not.
+    testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
     testImplementation("io.mockk:mockk:1.14.11")
     testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.8.1")
 }