Add a function for getting the number of days in the current month

[aslilac]

Recently I wrote some code for picking recurring dates. If it's supposed to recur monthly on a day that is acceptable in some months (January 31st) but not in others (January 31st) then it instead will happen on the last day of the month.

Currently I'm resorting to the following:

fn with_day_saturated<Tz: chrono::TimeZone>(datetime: DateTime<Tz>, day: u32) -> DateTime<Tz> {
	let day = day.clamp(1, 31);
	if datetime.day() == day {
		return datetime;
	}

	// We check back up to 3 days, because non-leap year February is the worst
	// case scenario. 31 - 3 = 28, which guarantees that we end up in bounds.
	datetime
		.with_day(day)
		.or_else(|| datetime.with_day(day - 1))
		.or_else(|| datetime.with_day(day - 2))
		.or_else(|| datetime.with_day(day - 3))
		.unwrap()
}

...which is obviously not ideal. 😅

It'd be great if there was some better way to figure out what the last day of the current month was. I could use that in the .clamp instead and delete half of this code.

[djc]

Would #1645 adequately address your use case?

[aslilac]

oh, yes, that's exactly what I was looking for! I just missed it somehow 😅

thanks!

[djc]

I think it hasn't been released yet...

[aslilac]

ah, that would explain it 😅 I just went to check again and it's definitely not there yet.

it also seems a bit clumsy to get to from a DateTime. best way I can see is to do something like:

let days_in_month = chrono::Month::try_from(datetime.month() as u8).unwrap().num_days(datetime.year()).unwrap();

bit unfortunate that .month() returns a number. idk what a good name would be for a variant that returns a Month value.

[djc]

Published 0.4.40. Feel free to submit a PR with a more suitable API, happy to review.