Represent 0 differently from "missing" in durations?

[littledan]

In Intl.DurationFormat, there are controls for which fields are displayed. One possibility is that this is phrased in terms of a "fields" option, with dash-separated field names. Another option is to list lower and upper fields, as described in tc39/proposal-intl-duration-format#2 .

For a different approach: What if the data model for Temporal.Duration treated 0 differently from null/undefined? Then, Intl.DurationFormat wouldn't need the fields to be specified, and could just format all of the fields that the Duration contains.

As a straw-person, I could imagine that .with({minute: null}) could remove the minute field (since undefined would be ignored).

cc @sffc @younies

[sffc]

This could work mechanically with regard to Intl.DurationFormat. I'm not sure about all of the implications. We should look at this alongside #337.

[ptomato]

I'm not a fan of this for two reasons:

• It's awkward with serialization, since P0Y0M1DT0H0M0S and P1D are defined to represent the same duration but we'd be treating them differently. Furthermore, { milliseconds: null, microseconds: 0 } would not be serializable.
• It doesn't affect any of the calculations in Temporal. Unspecified would always be treated as 0. The only thing it affects is formatting, which to me is an indication that the functionality belongs in Intl.DurationFormat.

[littledan]

I'm pretty convinced by @ptomato 's reasoning. If we go without a separate "missing" representation, I'm happy with @zbraniecki's suggestion for Intl.DurationFormation, removing the need for representing missing fields. I'm happy to drop this suggestion.