AsyncFunctionReturnsNull
AsyncFunction should not return a null Future, only a Future whose result is null.

Category
GUAVA
Severity
ERROR
Maturity

The problem

Methods like Futures.transformAsync and Futures.catchingAsync will throw a NullPointerException if the provided AsyncFunction returns a null Future. To produce a Future with an output of null, instead return immediateFuture(null).

Suppression

Suppress false positives by adding an @SuppressWarnings("AsyncFunctionReturnsNull") annotation to the enclosing element.