ICU4X 2.0 Dart bindings questions

[mosuem]

Date/Time formatting

• There are 6 different formatters - are they all needed?

  final icu.DateTimeFormatter? _dateTimeFormatter;
  final icu.DateFormatter? _dateFormatter;
  final icu.TimeFormatter? _timeFormatter;
  late final icu.ZonedDateTimeFormatter? _zonedDateTimeFormatter;
  late final icu.ZonedDateFormatter? _zonedDateFormatter;
  final icu.ZonedTimeFormatter? _zonedTimeFormatter;

• There are different constructors for zoned formatters, depending on the time zone format. But the timezone is parsed using icu.IanaParser() - why not just get the info from there?

        TimeZoneType.long => icu.ZonedDateTimeFormatter.specificLong,
        TimeZoneType.short => icu.ZonedDateTimeFormatter.specificShort,
        TimeZoneType.shortOffset =>
          icu.ZonedDateTimeFormatter.localizedOffsetShort,
        TimeZoneType.longOffset =>
          icu.ZonedDateTimeFormatter.localizedOffsetLong,
        TimeZoneType.shortGeneric => icu.ZonedDateTimeFormatter.genericShort,
        TimeZoneType.longGeneric => icu.ZonedDateTimeFormatter.genericLong,

• The time formatter takes alignment and timePrecision arguments, how do they map to ECMA402 DateTimeFormat options?
• What does TimeFormatStyle.full correspond to?

  icu.DateTimeLength timeTo4xOptions() => switch (this) {
    TimeFormatStyle.full => icu.DateTimeLength.long, //TODO: Does this match?
    TimeFormatStyle.long => icu.DateTimeLength.long,
    TimeFormatStyle.medium => icu.DateTimeLength.medium,
    TimeFormatStyle.short => icu.DateTimeLength.short,
  };

• How do I set a Calendar to be used?

[mosuem]

Also, is there a list of possible timezone values exposed somewhere? The parser must know what to parse for, right? It would be easier for users to select from a list of values than to have to guess strings.

[sffc]

• There are 6 different formatters - are they all needed?

They support different field sets, so you would need all the ones that correspond to field sets required by ECMA-402, which I believe is all of them.

• There are different constructors for zoned formatters, depending on the time zone format. But the timezone is parsed using icu.IanaParser() - why not just get the info from there?

Because they load different data. The match statement you wrote looks correct.

• The time formatter takes alignment and timePrecision arguments, how do they map to ECMA402 DateTimeFormat options?

You should use Alignment::Column if the ECMA options have "2-digit". You should use timePrecision to configure the time field set: whether to display hours only, hours and minutes, or hours, minutes, and seconds with optional fractional seconds.

• What does TimeFormatStyle.full correspond to?

Your mapping doesn't look right. It should be more like

ECMA Time Style	ICU4X Rust Code
Full	T::hms().zone(SpecificLong)
Long	T::hms().zone(SpecificShort)
Medium	T::hms()
Short	T::hm()

• How do I set a Calendar to be used?

In the locale.

[mosuem]

Because they load different data. The match statement you wrote looks correct.

But that can lead to errors, when users do things like (pseudocode) ZonedDateTimeFormatter.specificShort('America/Chicago'). Is there a list of possible timezone values exposed somewhere to avoid string inputs?

You should use Alignment::Column if the ECMA options have "2-digit". You should use timePrecision to configure the time field set: whether to display hours only, hours and minutes, or hours, minutes, and seconds with optional fractional seconds.

The 2-digit value is possible for hour, minute, second, day, month... Which one should I check for?

Your mapping doesn't look right. It should be more like

What is T::hms()? If the mapping is not right, what should icu.DateTimeLength be set to?

[sffc]

Because they load different data. The match statement you wrote looks correct.

But that can lead to errors, when users do things like (pseudocode) ZonedDateTimeFormatter.specificShort('America/Chicago'). Is there a list of possible timezone values exposed somewhere to avoid string inputs?

The argument to specificShort is the locale. Once constructed, the format functions work the same, except that not all of the zone styles require the same amount of granularity in the TimeZoneInfo.

You should use Alignment::Column if the ECMA options have "2-digit". You should use timePrecision to configure the time field set: whether to display hours only, hours and minutes, or hours, minutes, and seconds with optional fractional seconds.

The 2-digit value is possible for hour, minute, second, day, month... Which one should I check for?

Semantic skeletons don't support 2-digit for different fields, but fields like minute and second are always 2-digit anyway. I would use Alignment::Column if any of hour, day, or month are 2-digit, and see if it passes tests, which it most likely will.

Your mapping doesn't look right. It should be more like

What is T::hms()? If the mapping is not right, what should icu.DateTimeLength be set to?

ECMA Date Style	ICU4X Rust Code
Full	YMDE::long()
Long	YMD::long()
Medium	YMD::medium()
Short	YMD::short()