Bug #78590 [Com]: DatePeriod 0 Recurrences Throws Exception since 7.2.19

From: Date: Tue, 24 Sep 2019 20:37:40 +0000
Subject: Bug #78590 [Com]: DatePeriod 0 Recurrences Throws Exception since 7.2.19
References: 1  Groups: php.bugs 
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Edit report at https://bugs.php.net/bug.php?id=78590&edit=1

 ID:                 78590
 Comment by:         will dot baumbach at iselinc dot com
 Reported by:        will dot baumbach at iselinc dot com
 Summary:            DatePeriod 0 Recurrences Throws Exception since
                     7.2.19
 Status:             Open
 Type:               Bug
 Package:            Date/time related
 Operating System:   Linux
 PHP Version:        7.2.22
 Block user comment: N
 Private report:     N

 New Comment:

>This does not necessarily imply, though, that the final standard also allows zero recurrences.

Without purchasing the latest 2019 standard. In the 2000 final draft and 2016 draft, published in
2000 and 2019 respectively.

http://www.pvv.org/~nsaa/8601v2000.pdf
https://web.archive.org/web/20171020084445/https://www.loc.gov/standards/datetime/ISO_DIS%208601-1.pdf

"[n] represents digit(s), constituting a positive integer or zero;"
"Rn/..." 
"R/..."

Since the definition and format was specified identically in both drafts, I would say it is safe to
imply it also carried over into the published 2000 and 2019 final standards.

If copyrights permit and would help the PHP community, I would gladly purchase an applicable
published standard.


Previous Comments:
------------------------------------------------------------------------
[2019-09-24 10:57:37] cmb@php.net

Well, the ISO 8061 *draft*[1] indeed allows zero recurrences:

  recurringIndicator = "R", {digit}, "/" ;
  digit = positiveDigit | "0" ;

This does not necessarily imply, though, that the final standard
also allows zero recurrences.

[1] <https://web.archive.org/web/20171020084445/https://www.loc.gov/standards/datetime/ISO_DIS%208601-1.pdf>

------------------------------------------------------------------------
[2019-09-23 21:12:15] cmb@php.net

NEWS entry fixed with <http://git.php.net/?p=php-src.git;a=commit;h=ed099ab18642eb1815b43c71f3fb0326f723c69d>.
 Changelog fixed with <http://git.php.net/?p=web/php.git;a=commit;h=75024ae8bbe0a284518f620ab6c07f4c53288fd2>.

------------------------------------------------------------------------
[2019-09-23 20:22:08] will dot baumbach at iselinc dot com

>If you think that PHP should change its bug-fixing process so that all fixes resulting in a
>behavioral change must be postponed for the next series then you should bring it up on the internals
>mailing list. Until then, a bug fix is a bug fix.

This wasn't just a bug-fix, this is a backward incompatible change/BC Break as was stated in
the pull request, as it breaks the API.

A similar change for count($string) emitting a warning for an invalid argument, was held off for a
minor version where others suggested a major version.  https://github.com/php/php-src/pull/1672

So behavioral changes causing BC breaks is not something that appears to need to be addressed.

>0 means no repeating at all. If there's no repeating then there is no date range.

Period versus Range and Recurrence versus Occurrence.
For example a calendar event that repeats zero times.
The date period would reoccur 0 (zero) times, producing a date range with a single occurrence.

The old functionality would have produced a single date for the calendar event period as I
demonstrated.

return new DatePeriod($calendarDate, $repeatInterval, $repeats);

Instead repeats now has to be validated to return an Iterable or change the repeats to a
DateTimeInterface instead of an integer.

if ($repeats < 1) {
   return [$calendarDate];

   //or
   $endDate = clone $calendarDate;
   
   return new \DatePeriod($calendarDate, $repeatInterval, $endDate->add($repeatInterval));
}


>The current stance is that no recurrences is not permitted. Are you requesting that no
>recurrences be supported?

The ISO 8601 standard permits a repetition of 0 or more, 1 or more or n times.

https://web.archive.org/web/20171020084445/https://www.loc.gov/standards/datetime/ISO_DIS%208601-1.pdf
https://web.archive.org/web/20171020085148/https://www.loc.gov/standards/datetime/ISO_DIS%208601-2.pdf


"
Repetition (0 or more): {...}
Repetition (1 or more): {...}-
Repetition (n times): n * ...
"


If PHP is adhering to the ISO standards, then a repetition of 0 or more should be supported.

It appears the bug was with either the ISO 8601 repeating interval specification parsing not
accepting zero recurrences or the new DatePeriod::getRecurrences() feature in 7.2.17 returning NULL
instead of 0. https://3v4l.org/E8MT8

------------------------------------------------------------------------
[2019-09-23 17:04:57] requinix@php.net

> Shouldn't the update be reverted from a patch version to a minor version update.
> (affecting only 7.4+)? Since this
> is backward incompatible update, that changes the functional behavior of DatePeriod from PHP
> 5.3 to 7.2.18
If you think that PHP should change its bug-fixing process so that all fixes resulting in a
behavioral change must be postponed for the next series then you should bring it up on the internals
mailing list. Until then, a bug fix is a bug fix.

> since 0 is an acceptable range to repeat a date period
0 means no repeating at all. If there's no repeating then there is no date range.

The current stance is that no recurrences is not permitted. Are you requesting that no recurrences
be supported?

------------------------------------------------------------------------
[2019-09-23 16:35:07] will dot baumbach at iselinc dot com

Shouldn't the update be reverted from a patch version to a minor version update. (affecting
only 7.4+)? Since this is backward incompatible update, that changes the functional behavior of
DatePeriod from PHP 5.3 to 7.2.18

https://semver.org/

While updating the documentation is needed, the change will break current applications that accept a
0+ argument, forcing a refactor of the code to address the exception.

It should however throw an Exception if < 0 as opposed to < 1, since 0 is an acceptable range
to repeat a date period, where a negative or past date is not.

For example https://3v4l.org/ReWbN

$start = new DateTimeImmutable('2012-07-01');
$interval = new DateInterval('P1D');

$periodWithRecurrences = new \DatePeriod($start, $interval, $start->add($interval));
foreach($periodWithRecurrences as $date) {
    echo $date->format('Y-m-d') . \PHP_EOL;
}

echo \PHP_EOL;

$periodWithRecurrences = new DatePeriod($start, $interval, 0);
foreach($periodWithRecurrences as $date) {
    echo $date->format('Y-m-d') . \PHP_EOL;
}


Result 

2012-07-01

2012-07-01

------------------------------------------------------------------------


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