Roundup Tracker - Issues

Issue 2551208

Calender 'next month' link fails on day 31 of a month
Type: Severity: normal
Components: Versions:
Status: new
: : ThomasAH, rouilj, schlatterbeck
Priority: :

Created on 2022-06-01 08:40 by schlatterbeck, last changed 2022-06-01 09:38 by ThomasAH.

msg7550 Author: [hidden] (schlatterbeck) Date: 2022-06-01 08:40
The function html_calendar in roundup/cgi/ produces a help link that pops up a calendar for date selection.

This computes navigation links in the calendar:

date_prev_month = display + date.Interval("-1m")
date_next_month = display + date.Interval("+1m")

This fails on day 31 of a month due to limitations in our Date/Interval classes:

>>> from roundup import date
>>> d = date.Date ('2022-05-31')
>>> d + date.Interval ('+1m')
<Date 2022-07-01.00:00:00.000>
>>> d + date.Interval ('-1m')
<Date 2022-05-01.00:00:00.000>

Maybe that should be fixed by explicitly incrementing only the month of the given date.
On the other hand it only happens every two months :-)
msg7551 Author: [hidden] (schlatterbeck) Date: 2022-06-01 09:27
Looks like the Interval class *tries* to do the right thing by preserving the semantics of a month (and year, see below) but fails when the next/prev month doesn't have this particular day (the 31st).

So it also fails in leap years for the same reason:
>>> from roundup import date
>>> d = date.Date ('2024-02-29')
>>> d + date.Interval ('+1y')
<Date 2025-03-01.00:00:00.000>
>>> d + date.Interval ('-1y')
<Date 2023-03-01.00:00:00.000>

Turns out this may be seen as a bug of the Date / Interval implementation and not of the calendar?
Should we try to fix it there?
Looks like there are no tests for these corner cases and we might rule that the behavior was undefined before?
msg7552 Author: [hidden] (ThomasAH) Date: 2022-06-01 09:38
duplicate of issue2550858 (Month intervals at the end of long months yield the wrong day)
from 2014.

> On the other hand it only happens every two months :-)

In February this happens more often, because it has only 28/29 days :)

I'll add two patches over there that have been sitting in my backlog since 2019.
Date User Action Args
2022-06-16 23:19:49rouiljlinkissue2550858 superseder
2022-06-01 09:38:16ThomasAHsetnosy: + ThomasAH
messages: + msg7552
2022-06-01 09:27:12schlatterbecksetmessages: + msg7551
2022-06-01 08:40:42schlatterbeckcreate