Ensure public interface reliability: Tracking API compatibility for Android

Summary

This article explores how to ensure public API reliability by tracking compatibility changes, by exploring the RevenueCat SDK.Whether you’re building open-source libraries, SDKs, or common modules for other teams, it’s important to make deliberate and careful changes to public APIs, as they directly impact development resources required for migration. Unintentional or drastic API (Application Programming Interface) changes can break dependent projects and force consuming developers to spend time adapting to the new APIs. In this context, those developers are essentially your API users. In large-scale projects, tracking public API changes manually is error-prone and often overlooked. This article covers how to ensure your team stays fully aware of API changes by integrating plugins like Binary Compatibility Validator and Metalava into your project by exploring real-world examples from RevenueCat’s Android SDK. The approach When building an independent module that exposes public APIs, whether as a library, SDK, or common module, those APIs become part of a contract with other developers who consume them. Any changes to parameters, method names, or interface/class hierarchies can directly affect these users, potentially causing breakages or requiring significant effort to adopt newer versions. It’s not necessarily a problem if you’re fully aware of the API changes and communicate them properly. However, unintended or unnoticed changes to the API surface can lead to frustrating developer experiences for your library or SDK users/customers, especially when they encounter breaking changes you never intended to expose. Also, since Kotlin’s default visibility modifier is public, it’s easy to unintentionally expose or change APIs, making these kinds of issues more likely than you’d expect. Even if you’re not building a library or SDK, you can still apply this approach in a multi-module architecture to track which classes or interfaces are publicly exposed and potentially acc...