build: drop the AGP 9 built-in Kotlin opt-out

[AlvaroBrey]

• Removes the android.builtInKotlin=false and android.newDsl=false opt-out that build: update to AGP 9 (AGP 9.2.1, Gradle 9.4.1, Kotlin 2.2.21) #3964 added, from the root build and from both standalone sample builds, and takes kotlin-android out of 11 build scripts and the 3 convention plugins.
• ui/debugview/api.txt loses InternalDebugRevenueCatScreenViewModelFactory. Metalava now analyses the release variant, and that class lives in src/debug/kotlin. The release AAR contains zero occurrences of it, so it never shipped and the entry was wrong
• Fixes :dokkaGenerate, which is already broken on 11.0-dev. Built-in Kotlin registers Dokka source sets per Android variant instead of per Kotlin source set, and registers them lazily, so both :purchases and :ui:revenuecatui now select the documented variant through configureEach.
• Bumps androidx.navigation 2.5.3 to 2.9.8. safeargs 2.5.3 detects AGP through the old DSL and hard fails, so the navigation bump is a prerequisite for the new DSL rather than an independent upgrade.

Checklist

• If applicable, unit tests
• If applicable, create follow-up issues for purchases-ios and hybrids

Agent description

Motivation

AGP 9 enables built-in Kotlin and rejects the org.jetbrains.kotlin.android plugin outright:

The 'org.jetbrains.kotlin.android' plugin is no longer required for Kotlin support since AGP 9.0.

Opting out needs two flags together, android.builtInKotlin=false and android.newDsl=false, because the kotlin-android plugin casts the android extension to BaseExtension, which the new DSL drops. #3964 took that opt-out so the version bump stayed reviewable. AGP 10 removes the opt-out, so the migration has to happen regardless; doing it separately keeps the two diffs legible.

Description

Four things blocked the migration, each hidden behind the previous.

The old DSL extension types are gone. com.android.build.gradle.BaseExtension and com.android.build.gradle.LibraryExtension do not exist once the new DSL is active. The convention plugins now configure com.android.build.api.dsl.ApplicationExtension and com.android.build.api.dsl.LibraryExtension, and set compileSdk directly rather than calling compileSdkVersion(). KotlinAndroidProjectExtension stays as is: AGP's built-in Kotlin still registers it.

safeargs 2.5.3 cannot see AGP 9. It fails with safeargs plugin must be used with android plugin, because its detection goes through the old DSL. The 2.5.3 jar references com/android/build/gradle/BaseExtension, AppExtension and gradle/api/BaseVariant; the 2.9.8 jar references only com.android.build.api.variant.*. examples/purchase-tester is the only module applying the plugin, and it gets its own commit.

Dokka source sets changed shape. With the kotlin-android plugin, Dokka saw the Kotlin source sets and the config addressed main, defaults and customEntitlementComputation. Built-in Kotlin instead registers one source set per Android variant, and registers them after the dokka { } block runs, so named("defaultsRelease") throws even though the name is valid later. Both modules now select through matching { }.configureEach. :purchases keeps reportUndocumented, skipDeprecated, the Android external documentation link, both source links and the paywalls.components suppression, all moved onto the selected variant. The explicit customEntitlementComputation suppression is load-bearing, not redundant: Dokka defaults suppress to !isPublishable and customEntitlementComputationRelease is published, so it would otherwise be documented.

kotlin-test stops carrying JUnit. :feature:galaxy names kotlin-test-junit instead. Verified rather than inherited: with plain kotlin-test, org.junit.Test is unresolved across all 25 test methods.

Not visible in the diff: ./gradlew :dokkaGenerate fails on the base commit with Dokka cannot generate documentation for Android projects with multiple enabled variants that have common source roots. The docs-deploy job that runs it is gated on release tags, so #3964 never exercised it. This PR is what makes it pass again, which is a bigger deal than the diff makes it look.

Worth noting separately: AGP 9.2.1 declares kotlin-gradle-plugin:2.2.10, so built-in Kotlin takes its compiler from buildscript classpath resolution rather than from our catalog. Confirmed the published contract from #3964 is intact rather than assumed:

check	result
resolved KGP	2.2.21, not AGP's bundled 2.2.10
:purchases POM	kotlin-stdlib:2.2.21 at compile scope
release AAR metadata	mv=[1,8,0], so languageVersion 1.8 survives

Regression gates

• ./gradlew :dokkaGenerate for the Dokka rework. Generates 1367 pages with com.revenuecat.purchases.paywalls.components still suppressed.
• :feature:galaxy:testDefaultsDebugUnitTest for the kotlin-test-junit swap. Needs --rerun-tasks: a cached run passes even with the dependency reverted, which is how this could slip through.
• :examples:purchase-tester:assembleDebug for the navigation bump.

Rejected:

• Wiring the Dokka variant selector to ANDROID_VARIANT_TO_PUBLISH instead of hardcoding "defaultsRelease" twice. fastlane/Fastfile:295 rewrites that property per publish, so a customEntitlementComputation publish would point Dokka at exactly the variant :purchases suppresses.
• Hoisting the shared Dokka config into ConfigureDokka.kt. Dokka's types are not on build-logic's compile classpath, so it needs the reflection pattern from ConfigureMetalava.kt, and sharing reportUndocumented.set(true) would newly turn it on for the four public-library modules that have no dokka { } block.
• Moving the five hand-rolled app modules onto revenuecat-android-application, which would collapse 5 of the 6 per-module edits. Each keeps 2 to 3 overrides, and both testpurchases* modules deliberately pin old compileSdk/targetSdk to test compatibility. Worth a separate PR, not this one.

Limitations:

• examples/MagicWeather and test-apps/sdksizetesting still apply kotlin-android. They are separate builds pinned to AGP 8.13.2, so they keep the plugin correctly and are untouched.
• purchases/build.gradle.kts:120 has a dead androidComponents { onVariants } block guarding a "free" product flavor that does not exist in the repo. Pre-existing and unrelated, left alone.

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Note

Medium Risk
Wide Gradle/AGP convention changes affect every Android module’s compile and doc generation; navigation and Dokka behavior are prerequisites for CI release docs, with limited runtime SDK impact.

Overview
Completes the AGP 9 migration by removing the android.builtInKotlin=false / android.newDsl=false opt-outs and dropping org.jetbrains.kotlin.android across convention plugins, app modules, samples, and the version catalog.

Build-logic now configures ApplicationExtension / LibraryExtension from the new DSL (e.g. compileSdk instead of BaseExtension). :purchases and :ui:revenuecatui Dokka blocks use matching { }.configureEach so documentation targets defaultsRelease and suppresses customEntitlementComputation variants after AGP registers per-variant source sets lazily.

androidx.navigation is bumped 2.5.3 → 2.9.8 so Safe Args works with the new DSL. :feature:galaxy switches unit tests to kotlin-test-junit. ui/debugview/api.txt drops InternalDebugRevenueCatScreenViewModelFactory (debug-only; not in the release API Metalava analyzes).

^{Reviewed by Cursor Bugbot for commit e45c589. Bugbot is set up for automated code reviews on this repo. Configure here.}

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	maven/​org.jetbrains.kotlin/​kotlin-test-junit@​2.2.21

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[RevenueCat-Danger-Bot]

Public API changes in ui:debugview (2 removed)

- public final class InternalDebugRevenueCatScreenViewModelFactory extends androidx.lifecycle.ViewModelProvider.NewInstanceFactory
- ctor public InternalDebugRevenueCatScreenViewModelFactory(kotlin.jvm.functions.Function1<? super com.revenuecat.purchases.models.StoreTransaction,kotlin.Unit> onPurchaseCompleted, kotlin.jvm.functi…

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[emerge-tools]

📸 Snapshot Test

31 modified, 590 unchanged

Name	Added	Removed	Modified	Renamed	Unchanged	Errored	Approval
TestPurchasesUIAndroidCompatibility Paparazzi com.revenuecat.testpurchasesuiandroidcompatibility.paparazzi	0	0	31	0	251	0	✅ Approved
TestPurchasesUIAndroidCompatibility com.revenuecat.testpurchasesuiandroidcompatibility	0	0	0	0	339	0	N/A

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.25%. Comparing base (08343dc) to head (e45c589).

Additional details and impacted files

@@            Coverage Diff            @@
##           11.0-dev    #4120   +/-   ##
=========================================
  Coverage     83.25%   83.25%           
=========================================
  Files           448      448           
  Lines         18110    18110           
  Branches       2744     2744           
=========================================
  Hits          15077    15077           
  Misses         2140     2140           
  Partials        893      893           

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[tonidero]

Looks good! Thank you!