On Tue, 28 Mar 2023 21:06:34 GMT, Justin Lu <j...@openjdk.org> wrote:
>> This PR fixes the bug which occurred when `Calendar.roll(WEEK_OF_YEAR)`
>> rolled into a minimal first week with an invalid `WEEK_OF_YEAR` and
>> `DAY_OF_WEEK` combo.
>>
>> For example, Rolling _Monday, 30 December 2019_ by 1 week produced _Monday,
>> 31 December 2018_, which is incorrect. This is because `WEEK_OF_YEAR` is
>> rolled from 52 to 1, and the original `DAY_OF_WEEK` is 1. However, there is
>> no Monday in week 1 of 2019. This is exposed when a future method calls
>> `Calendar.complete()`, which eventually calculates a `fixedDate` with the
>> invalid `WEEK_OF_YEAR` and `DAY_OF_WEEK` combo.
>>
>> To prevent this, a check is added for rolls into week 1, which determines if
>> the first week is minimal. If it is indeed minimal, then it is checked if
>> `DAY_OF_WEEK` exists in that week, if not, `WEEK_OF_YEAR` must be
>> incremented by one.
>>
>> After the fix, Rolling _Monday, 30 December 2019_ by 1 week produces
>> _Monday, 7 January 2019_
>
> Justin Lu has updated the pull request incrementally with five additional
> commits since the last revision:
>
> - Impl cleanup, add Saturday end day conditional
> - Rename test, clarify test documentation
> - Add type to static declaration of Cal.Builder, since only concerned with
> Gregorian for this test
> - Pass in amount as 1 directly
> - Reuse Calendar.Builder
src/java.base/share/classes/java/util/GregorianCalendar.java line 3014:
> 3012: */
> 3013: private boolean dayInMinWeek (int day, int startDay, int endDay) {
> 3014: endDay = endDay == 0
Why `endDay` can be `0`? If the arguments are `Calendar.XXXDAY`, should they be
between 1 to 7? In other words, why is the above calling site doing
`getFirstDayOfWeek() - 1`?
I'd add some range checks for the input values.
test/jdk/java/util/Calendar/RollFromLastToFirstWeek.java line 52:
> 50: */
> 51: public class RollFromLastToFirstWeek {
> 52: static Calendar.Builder GREGORIAN_BUILDER = new Builder()
Nit: `Calendar.` can be omitted (and can be `private static final`)
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13031#discussion_r1152579044
PR Review Comment: https://git.openjdk.org/jdk/pull/13031#discussion_r1152579338
