Clarify model class fields interface regarding mandatory / optional / default values #44
Description
The model classes is our internal main reference regarding the specification of optional/mandatory fields. Currently we uses Optional<T> when a field is marked as optional in the specs, with another getter supplying by design a non-null value with a default. However Optional is better understood in language context, and since we are inside a validator, even mandatory value can be null.
We should clarify how to model the following:
- Mandatory values:
- that cannot be null by design, such as a mandatory ID in DAO scope. Example: stop time trip ID.
- that can be null for invalid input data:
- without a sensible default to use by a validator. Example: stop name
- with a sensible default to use by a validator. Example: route type, in speed checks we can fallback on a default type to get the max speed
- Optional values:
- that have a default value provided by the specs. Example: timepoint, pickup/dropoff type, route colors...
- that do not have a default value provided by the specs:
- with a sensible default value that can be used by validators. Example: ?
- without a sensible default value that can be used by validators. Here a null is valid. Example: route URL.
- Conditionally required, for example stop name (where boarding areas or generic nodes make it optional), parent_station...
Maybe creating dedicated holders such as Optional<T>, for example Required<T> etc...