gdbus-codegen not generating nullable annotation
Since Bug 660879, g-i has supported "(nullable)" annotations for param and return values, but gdbus-codegen does not seem to be generating these.
For example, the GOA method goa_object_get_account which is generated by gdbus-codegen includes generated (I assume?) documentation that states the return could be null, but the
(nullable) annotation is missing from the generated source, and hence also from the GIR.
This is useful for bindings for languages like Vala and Haskell that care about nullability, so it would be good to gdbus-codegen generating the annotation when it knows a return (or param) value could be null.