Android API 23 crash: generated server descriptor uses `java.util.Base64`

[denis-bezrukov]

We hit a runtime crash using wire-grpc-server in an Android app that exposes a gRPC server on Android 6 / SDK 23.

Dependencies:

• com.squareup.wire:wire-gradle-plugin / wire-runtime: 5.4.0
• com.squareup.wiregrpcserver:server / server-generator: 1.0.0-alpha04
• com.squareup.okio:okio: 3.9.0
• Kotlin: 2.0.21
• AGP: 8.11.2
• minSdk: 23

The generated *WireGrpc.kt contains:

val bytes = java.util.Base64.getDecoder().decode(str)

On Android 6 / SDK 23, java.util.Base64 is unavailable, so the server crashes when binding the service:

NoClassDefFoundError: Failed resolution of: Ljava/util/Base64;
at ...AppNameServerWireGrpc.descriptorFor(...)
at ...AppNameServerWireGrpc$AppNameServerImplBase.bindService(...)

This looks similar to square/wire#3127, but in this case the java.util.Base64 usage is emitted by the wire-grpc-server generator for server descriptors.

We can work around it by enabling Android core library desugaring. Would you consider either avoiding java.util.Base64 in generated Android-compatible server code, or documenting that server users with minSdk < 26 need coreLibraryDesugaring?

One possible alternative is Okio's Base64 support, for example String.decodeBase64(), since Okio is already part of the Wire stack.