Duration Infinity is converted to 0 by some methods

[jsejcksn]

Describe the bug

I see that Infinity has been discussed in some other issues, but I don't see discussion around Duration.

Luxon treats Infinity as a valid duration, but some methods return 0 as the value representation.

To Reproduce

Here's an inexhaustive example which demonstrates inconsistency:

const dur = Duration.fromMillis(Number.POSITIVE_INFINITY);
dur.equals(Duration.fromMillis(Number.POSITIVE_INFINITY)); //=> true
dur.isValid; //=> true
dur.invalidReason; //=> null
dur.invalidExplanation; //=> null
dur.milliseconds; //=> Infinity
dur.toObject(); //=> { milliseconds: Infinity }
dur.normalize().toObject(); //=> { milliseconds: Infinity }
dur.toHuman(); //=> '∞ milliseconds'
dur.toISO(); //=> 'PTInfinityS'
dur.toString(); //=> 'PTInfinityS'

// 🤨
dur.toMillis(); //=> 0
dur.valueOf(); //=> 0
dur.as('milliseconds'); //=> 0
dur.toFormat('S'); //=> 0

Actual vs Expected behavior

The latter methods above should also return a representation of Infinity, and not 0.

Version information

Key	Value
OS	macOS
Browser	Chrome 100.0.4896.88
Luxon	2.3.1

[icambron]

I'd take fixes for that. What should toISO() return, though? I'm pretty sure PTInfinityS is bad, and is just the result of toString()ing the number

[jsejcksn]

What should toISO() return, though? I'm pretty sure PTInfinityS is bad, and is just the result of toString()ing the number

@icambron From my research (note that I haven't purchased the updated, full text of the standard, so I don't have access to read any deviations from what has been published in open drafts) ISO 8601 and its extensions don't address an infinite duration.

In an extension, open-ended intervals are defined using .. notation (e.g. ../2022-04-23 or 1900-01-01/..). Section 3.7 "Mutual agreement" describes using valid syntax with invalid values by agreement between parties, and this has given rise to such usage as 9999-13-00 to represent an indefinite future date by convention only.

So... the direct answer to your question is that, currently, there is no valid ISO representation of an infinite duration.

With the above in mind:

Perhaps it is sensible to consider infinite durations as invalid, and to create a new enumeration for the invalidReason property such as "infinite duration".

(Speaking of enumerations, can you point me to where the ones produced internally are located? It seems useful at minimum, and even necessary in some cases to have access to those enumerations for matching during error-handling and testing, but I didn't find them in a search of the repository.)

IMO, while PTInfinityS is absolutely not spec, it is a logical and useful representation to a human. I don't know whether or not invalid Luxon durations have a toISO() method: if so, would spec compliance matter in that case?

Ultimately, I have a need to represent infinite durations and want a reliable way to know whether a duration is infinite or not.

[icambron]

Thinking about this a bit more, I agree with this:

Perhaps it is sensible to consider infinite durations as invalid, and to create a new enumeration for the invalidReason property such as "infinite duration".

They're just not going to work in a consistent way, and we should just ban them.

Somewhat embarassingly, there's no enum, they're just strings. For example, in Duration.fromISO(), you see this line:

      return Duration.invalid("unparsable", `the input "${text}" can't be parsed as ISO 8601`);

"unparsable" becomes invalidReason and that second arg becomes invalidExplanation. The idea is that the first one is really an enumeration and the second one might have specific details in it.

[Maxim-Mazurok]

I'm also having trouble representing an infinite duration, my use case is representing a lifetime warranty.
I was doing this: Duration.fromObject({ days: Infinity }).shiftToAll().toHuman() which returns NaN years, NaN months, NaN weeks, NaN days, NaN hours, NaN minutes, NaN seconds, NaN milliseconds

Trying to use an open interval Interval.fromDateTimes(DateTime.now(), DateTime.fromMillis(Infinity)) produces an error: {"e": undefined, "invalid": {"explanation": null, "reason": "missing or invalid end"}, "isLuxonInterval": true, "s": undefined}