From 22131fce238493ac861d1243eff91541c9a9fae9 Mon Sep 17 00:00:00 2001
From: Gabriel Donadel Dall'Agnol <donadeldev@gmail.com>
Date: Thu, 3 Sep 2026 11:20:57 -0300
Subject: [PATCH] fix(android): skip explicit Kotlin plugin when AGP registers
 the kotlin extension (#1934)
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## Problem

Android Gradle Plugin 9 ships built-in Kotlin support and enables it by default, so AGP
registers the `kotlin` extension itself. When a library *also* applies `kotlin-android`
explicitly, the two collide and configuration fails before anything compiles:

```
> Failed to apply plugin 'kotlin-android'.
   > Cannot add extension with name 'kotlin', as there is an extension already registered with that name.
```

The apply is unconditional in both files, so on an AGP 9 project this library cannot be
built at all. There is no consumer-side workaround short of patching the file — setting
`android.builtInKotlin=false` project-wide just to build one dependency is not a
reasonable ask, and that escape hatch is removed in AGP 10.

## Change

Apply the plugin only when nothing has registered the `kotlin` extension yet:

```groovy
if (project.extensions.findByName('kotlin') == null) {
    apply plugin: 'kotlin-android'
}
```

Files changed:

- `android/build.gradle`
- `react-native-purchases-ui/android/build.gradle`

This checks the exact condition that fails, so there is no AGP version table to keep in
sync. It follows the approach already used in
[purchases-capacitor#860](https://github.com/RevenueCat/purchases-capacitor/pull/860) and
[purchases-flutter#1765](https://github.com/RevenueCat/purchases-flutter/pull/1765), per
maintainer review on this PR.

Behaviour across configurations:

| AGP | `android.builtInKotlin` | `kotlin` extension | explicit apply |
|---|---|---|---|
| 8.x | unset or `false` | absent | yes (unchanged) |
| 9.x | unset or `true` | registered by AGP | no |
| 9.x | `false` | absent | yes |
| 10+ | n/a (opt-out removed) | registered by AGP | no |

The check sits after `apply plugin: 'com.android.library'` in both files, so AGP has
already registered its extensions by the time it runs.

## What I verified, and what I did not

- **Verified end to end** on a real Expo SDK 58 / React Native 0.87 project with AGP
  9.2.1 and Gradle 9.4.1: `:app:assembleDebug` succeeds both with
  `-Pandroid.newDsl=true -Pandroid.builtInKotlin=true` and with both flags off.
- Confirmed both branches actually execute, rather than one path silently always being
  taken: with the flags off, `:<module>:compileDebugKotlin` runs from the explicitly
  applied plugin; with them on, the build succeeds without it, which it could not do if
  the plugin were still being applied.
- Syntax-checked both files with Groovy's `Phases.CONVERSION`.
- **Not run:** this repo's own CI or example app. You mentioned you'd handle AGP 9 CI
  coverage separately.

Found while sweeping 157 popular React Native libraries for AGP 9 new-DSL compatibility.
34 failed with the new DSL enabled, and 29 of those failed on exactly this — it is the
most common blocker by a wide margin.
---
 android/build.gradle                           | 8 +++++++-
 react-native-purchases-ui/android/build.gradle | 8 +++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/android/build.gradle b/android/build.gradle
index a8a2416fb..9ec049bb5 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -12,7 +12,13 @@ buildscript {
 }
 
 apply plugin: 'com.android.library'
-apply plugin: 'kotlin-android'
+// AGP 9 ships built-in Kotlin support and registers the `kotlin` extension
+// itself. Applying kotlin-android on top of it fails with
+// "Cannot add extension with name 'kotlin'". Only apply it when nothing
+// has registered that extension yet.
+if (project.extensions.findByName('kotlin') == null) {
+    apply plugin: 'kotlin-android'
+}
 
 def getExtOrDefault(name) {
     return rootProject.ext.has(name) ? rootProject.ext.get(name) : project.properties['Purchases_' + name]
diff --git a/react-native-purchases-ui/android/build.gradle b/react-native-purchases-ui/android/build.gradle
index 1309b9cda..ec7984851 100644
--- a/react-native-purchases-ui/android/build.gradle
+++ b/react-native-purchases-ui/android/build.gradle
@@ -19,7 +19,13 @@ def isNewArchitectureEnabled() {
 }
 
 apply plugin: "com.android.library"
-apply plugin: "kotlin-android"
+// AGP 9 ships built-in Kotlin support and registers the `kotlin` extension
+// itself. Applying kotlin-android on top of it fails with
+// "Cannot add extension with name 'kotlin'". Only apply it when nothing
+// has registered that extension yet.
+if (project.extensions.findByName('kotlin') == null) {
+    apply plugin: "kotlin-android"
+}
 
 if (isNewArchitectureEnabled()) {
   apply plugin: "com.facebook.react"