Considering the possibility to represent `0` of some `DateTimeUnit`?

[kevincianfarini]

Right now all of the instances of DateTimeUnit guard against instantiating with zero of the underlying asset. For example:

@Serializable(with = DayBasedDateTimeUnitSerializer::class)
public class DayBased(
    /**
     * The length of this unit in days.
     */
    public val days: Int
) : DateBased() {
    init {
        require(days > 0) { "Unit duration must be positive, but was $days days." }
    }

This feels really unintuitive. If someone is dynamically performing math operations of Instant, LocalDate, etc. it should be permissible to have an identity operation. Currently this requires null coalescing for identity-like operations. Eg:

val dateTimeUnit: DateTimeUnit? = /* TODO */
val date = clock.now().toLocalDate(/* omitted */).let { date ->
  if (dateTimeUnit == null) date else date.minus(dateTimeUnit)
} 

I'm hoping to understand the rationale for why zero of some DateTimeUnit is generally prohibited. Thank you!

[ilya-g]

DateTimeUnit is not an alternative for Duration or DateTimePeriod. If you want to add zero of some DateTimeUnit, use the overload that takes an integer and that DateTimeUnit.
We're considering deprecating the overloads of plus and minus with a single DateTimeUnit parameter to avoid this confusion, see #95 (comment)

[kevincianfarini]

That makes more sense, thank you!