176 mappers should never return null

[zartc]

Here's the code that implements the ban of null return values from mappers.

• null return values from domain->proto mapper will end up with a NPE thrown by Protobuff.
• null return values from proto->domain is less dangerous but it is best to let the application decide what to do in a post-mapper step.

The changes consist of systematically return a "default' value: empty string or arrays, EPOCH, zero, or protobuff's getDefaultInstance.

Close #176

[seime]

@zartc Sorry for the late response,

I agree with your reasoning. On the proto->domain side I would like to see 2 different implementations, yours (map to empty domain) as well as the existing one (map to null).

If we split the existing mapper class into 3 variants

• DomainToProto
• ProtoToEmptyDomain
• ProtoToNullDomain

the developer can select the appropriate implementation based on his/her needs. It also avoid breaking (runtime) any existing use of this library (mapper uses attribute must be updated, but this is detected compile time)

[wirekang]

Any news?