Unexpected / unintuitive behaviour of Duration.minus()

[ipg0]

Describe the bug Subtracting seconds from a Duration defined in days results in unchanged number of days and negative seconds, which might not be expected behaviour.

Also, couldn't find any documentation on whether this might be expected behaviour, so I would assume it is not.

To Reproduce Here's the issue reproduced in Node REPL v18.18.0

Welcome to Node.js v18.18.0.
Type ".help" for more information.
> const luxon = require('luxon')
undefined
> let d = luxon.Duration.fromObject({days: 7})
undefined
> let d1 = d.minus({seconds: 1})
undefined
> d1.toObject()
{ days: 7, seconds: -1 }

Actual vs Expected behavior Subtraction of seconds from a Duration is, presumably, expected to result in a Duration object containing a valid representation of a duration of time. However, the result above (7 days and -1 seconds) is clearly not a valid representation of it.

Desktop (please complete the following information):

• OS: Linux 6.2.0-33-generic Ubuntu 23.04 x86_64
• Browser: Chromium-based, also Node v18.18.0
• Luxon version 3.4.3 (as per luxon.VERSION called from Node)
• Your timezone Russia/Moscow

[icambron]

It is a valid representation. In fact, it's the only one that is completely clean: days are not necessarily all the same length, so to do basically anything else, Luxon would have to do some converting in not-completely-always-right ways. A rule we try to follow with Luxon is to not do any conversions unless you ask for it.

Which you can do:

d1.normalize().toObject() //=> { days: 6, seconds: 86399 } 
d1.shiftTo("days").toOject() // =>  { days: 6.999988425925926 } 
d1.shiftTo("days", "hours", "minutes", "seconds").toObject()   //=> { days: 6, hours: 23, minutes: 59, seconds: 59 }