This repository is a minimal reproducible project for a bug related to AGP 9 and Gradle Cache.

A library built with AGP 8 that contains an invalid ProGuard/R8 rule (-printmapping) in its consumer-rules.pro will:

• Build successfully when consumed by an application using AGP 8
• Break the Gradle build cache on the second run when consumed by an application using AGP 9

The root cause is the -printmapping consumer ProGuard rule bundled inside the AAR. AGP 8 silently ignores or accepts this rule in the consuming app's context. AGP 9 processes it differently, causing a cache invalidation or error on incremental/cached builds.

agp-9-issue/
├── test.sh              # Reproduction script
├── lib-agp-8/           # Android library built with AGP 8.13.2 / Gradle 8.14.4
│   └── lib/
│       └── consumer-rules.pro   # Contains the problematic rule: -printmapping out.map
├── app-agp-8/           # Android app (AGP 8.13.2 / Gradle 8.14.4) — consumes lib-agp-8 AAR
└── app-agp-9/           # Android app (AGP 9.0.1 / Gradle 9.3.1)   — consumes lib-agp-8 AAR

lib-agp-8/lib/consumer-rules.pro:

-printmapping out.map

This consumer rule is bundled into lib-release.aar when the library is built with AGP 8. The rule is valid in AGP 8's context but causes a Gradle cache problem in AGP 9 when the AAR is consumed by an application.

Run the test script from the repository root:

./test.sh

The script performs the following steps:

1. Build the library (lib-agp-8) with AGP 8 — produces lib-release.aar containing the -printmapping out.map consumer rule.
2. Build the AGP 8 app (app-agp-8) twice:
   • Gradle cache is cleared and the project is cleaned beforehand
   • First run: cold build
   • Second run: incremental/cached build
   • Expected result: both runs succeed.
3. Build the AGP 9 app (app-agp-9) twice:
   • Gradle cache is cleared and the project is cleaned beforehand
   • First run: cold build
   • Second run: incremental/cached build
   • Expected result: first run succeeds, second run fails.

Each app project uses an isolated Gradle home (-g .gradle-home) to avoid cross-project cache interference.