The java-shell source code currently does not expect every function labelled with @returnsPromise to actually return a Promise, and instead relies on the synchronous result from its own service provider being passed along. This requires us to do a small hack in the @returnsPromise decorator.

We should:

• Be consistent and make sure that all methods labelled with @returnsPromise actually return a Promise, e.g. by making them async functions (we could test that)
• Update the java-shell to handle those cases where it doesn’t already.