ProGuard rules for Retrofit

App was crashing in release builds with ProGuard enabled. The issue was with Retrofit models.

ProGuard obfuscates class names and removes unused code, but Retrofit uses reflection to serialize/deserialize JSON. If the model classes get obfuscated or removed, Retrofit can't work.

You need to keep your model classes:

# Keep Retrofit interfaces
-keep,allowobfuscation,allowshrinking interface retrofit2.Call
-keep,allowobfuscation,allowshrinking class retrofit2.Response

# Keep your model classes
-keep class com.example.models.** { *; }

# Or if using Gson
-keepattributes Signature
-keepattributes *Annotation*
-keep class sun.misc.Unsafe { *; }
-keep class com.google.gson.** { *; }

But here's what got me - if you're using generic types in your models, you need to keep the generic signature. ProGuard removes generic type information by default, which breaks Gson/Moshi.

Also, if your models have generic fields like List<SomeType>, make sure SomeType is also kept. ProGuard might remove it if it thinks it's unused.

One more thing - if you're using Kotlin data classes, make sure you're keeping the synthetic methods that Gson/Moshi use. Sometimes ProGuard removes getters/setters that it thinks are unused.

The easiest solution is to add @Keep annotation to your model classes, or use -keep rules for the entire package containing your models.

Thanks for reading! Check out more posts on the blog if you'd like.