AGP 9: build fails on getDefaultProguardFile('proguard-android.txt')

[docayapay-wq]

Bug

Building an app that includes this plugin fails with Android Gradle Plugin 9.0 because android/build.gradle passes proguard-android.txt to getDefaultProguardFile(). AGP 9 rejects that file outright — it contains -dontoptimize, which disables R8 optimizations for the whole build.

* Where:
Build file '.../node_modules/@capacitor-community/admob/android/build.gradle'

* What went wrong:
A problem occurred evaluating project ':capacitor-community-admob'.
> `getDefaultProguardFile('proguard-android.txt')` is no longer supported since it includes
  `-dontoptimize`, which prevents R8 from performing many optimizations. Instead use
  `getDefaultProguardFile('proguard-android-optimize.txt)`, and if needed, temporarily use
  `-dontoptimize` in a custom keep rule file while fixing breakages.

Source

https://github.com/capacitor-community/admob/blob/main/android/build.gradle — the release build type:

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

Suggested fix

Switch to the optimizing variant, which is what AGP recommends and what the app module template has used for years:

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

Since minifyEnabled false is set here, this line has no effect on the library build itself — but it does block consuming apps from configuring AGP 9 at all, because the failure happens during project evaluation.

Why this matters beyond AGP 9

Google Play Console now actively recommends upgrading to AGP 9 under "R8 optimization" in the release dashboard, so apps that depend on this plugin cannot act on that recommendation.

Separately, -dontoptimize is a global R8 directive: if any dependency contributes it through consumer ProGuard rules, optimization is disabled for the entire app and there is no way to re-enable it from the app module. We hit exactly that in this app through a different dependency — Play Console reported "App optimization below our threshold — Optimization 0%" and the AAB's BUNDLE-METADATA/com.android.tools/r8.json showed isOptimizationsEnabled: false. Removing the offending module brought it back to true. Worth avoiding proguard-android.txt for that reason alone.

Environment

@capacitor-community/admob	8.1.0
@capacitor/android	8.5.1
AGP	9.0.0
Gradle	9.1.0
Kotlin Gradle plugin	2.2.20
compileSdk / targetSdk	36

Reproduction

1. In a Capacitor 8 app with this plugin, set AGP to 9.0.0 and the Gradle wrapper to 9.1.0.
2. gradle.properties: android.builtInKotlin=false and android.newDsl=false (both currently required — AGP 9's built-in Kotlin support conflicts with kotlin-android, and AGP itself suggests newDsl=false as the temporary workaround).
3. Run ./gradlew :app:assembleRelease.

Note that compileSdk is already specified in 8.1.0, so the earlier AGP 9 error about a missing compileSdk no longer occurs — this ProGuard line is the remaining blocker.