On 11/08/2016 02:49 PM, Derick Rethans wrote:
Hi,
On Tue, 8 Nov 2016, Arjen Schol wrote:
I think you make some bad assumptions here.
Please don't top-reply on this list.
The examples provided by Sjon are
scripts submitted to 3v4l.org They may have bad assumptions, but are real life
examples of DateTime usage. And they will break.
They already could break. As Dan wrote better:
> Having bugs happen more frequently is a good thing. It stops
> you from ignoring edge cases and programming by coincidence.
We have two issues in our codebase. We ARE testing RC release, I think
feedback should be taken seriously.
Taking things seriously does not mean having to agree.
Taking things seriously means reading the complete message and not
focussing on a detail of an example (https://3v4l.org/YUhFF faces the
same problem without constructor argument; e.g. not easy to set
microseconds to 0). I've never said we were facing new DateTime == new
DateTime problems, but Dan gives a lesson on bad assumptions...
No comment on not being able to set microtime to zero.
1. We overloaded DateTime::setTime, this needed an update because of the extra
parameter (point 3). BC break.
PHP throws a warning here, but the expected result of the code
execusion is correct:
[PHP: 7.1.0-dev ] derick@whisky:/tmp $ cat doo.php
<?php
class MyDate extends DateTimeImmutable
{
function setTime( $h, $i, $s )
{
return parent::setTime( $h, $i + 5, $s );
}
}
$a = new MyDate();
$b = $a->setTime( 2, 5, 10 );
var_dump( $a, $b );
?>
[PHP: 7.1.0-dev ] derick@whisky:/tmp $ php -n doo.php
Warning: Declaration of MyDate::setTime($h, $i, $s) should be
compatible with DateTimeImmutable::setTime($hour, $minute, $second = NULL,
$microseconds = NULL) in /tmp/doo.php on line 9
object(MyDate)#1 (3) {
["date"]=>
string(26) "2016-11-08 13:30:06.371428"
["timezone_type"]=>
int(3)
["timezone"]=>
string(3) "UTC"
}
object(MyDate)#2 (3) {
["date"]=>
string(26) "2016-11-08 02:10:10.000000"
["timezone_type"]=>
int(3)
["timezone"]=>
string(3) "UTC"
}
This is at *most* a BC break because it shows a warning. The code itself isn't
broken.
In PHP 5.6, this was a E_STRICT warning, which got converted to E_WARNING in
PHP 7.0:
[PHP: 5.6.28-dev ] derick@whisky:~/dev/php/php-src.git $ php -n
-derror_reporting=-1 -ddate.timezone=UTC /tmp/doo.php
Strict Standards: Declaration of MyDate::setTime() should be compatible
with DateTimeImmutable::setTime($hour, $minute, $second = NULL) in /tmp/doo.php
on line 9
…
[PHP: 7.0.13-dev ] derick@whisky:~/dev/php/php-src.git $ php -n
-derror_reporting=-1 -ddate.timezone=UTC /tmp/doo.php
Warning: Declaration of MyDate::setTime($h, $i, $s) should be
compatible with DateTimeImmutable::setTime($hour, $minute, $second = NULL) in
/tmp/doo.php on line 9
…
As this specific overloading does *not* violate the Liskov Substitution
Principle, I would argue that it is this *warning* that is the BC break in PHP
7.0, and not the addition of the extra argument-with-default-value.
I think it DOES violate (and hence the warning) LSP. If you DO use the
4th microseconds argument in your application, you cannot replace a
DateTime object with CustomDate which does not have this 4th argument,
even tough DateTime has a default value for it. If you do want to save a
time with microseconds by setTime, you end up without microseconds if
you replace DateTime with CustomDate.
"[..] if S is a subtype of T, then objects of type T may be replaced
with objects of type S (i.e., an object of the type T may be substituted
with its subtype object of the type S) without altering any of the
desirable properties of that program (correctness, task performed, etc.)"
2. We test the following:
A. $date = new DateTime;
B. Store in database.
C. Retrieve datetime.
D. $fromDatabase = new DateTime(storedDateTime);
E. $fromDatabase == $date (which fails now, because $date has microsecond
precision while $fromDatabase doesn't).
If you don't store microseconds in the database, then I expect that not
to work. It's like if you wouldn't store seconds in the database, that
you wouldn't get the same result either.
This used to work for 7 years, and now it's not. If I hadn't stored
seconds, it wouldn't have worked for 7 years.
Where does this have a bad assumption? We tested an assumption (DateTime has
seconds precision), and now it fails. Is that a bad assumption? I think it's
just backward breaking with no good way to fix the code.
The bad assumption is, that DateTime has always had microseconds
precision, and the bug that got fixes was, that they did not always get
correctly initialised:
First, it was virtually impossible to create a DateTime object with the
current time WITH microseconds set (DateTime::createFromFormat('U.u',
sprintf('%.f', microtime(true))); only method AFAIK) and now it is
cumbersome to create a DateTime object without microseconds
initialized/set to 0: DateTime::createFromFormat('U', time()); or new
DateTime('@' . time()); or afterwards by calling setTime()...
This has been the case since 5.3.1.. You can't seriously argue DateTime
always had microsecond precision and fixing the initialization took
almost 7 years..
DateTime had some obscure way to initialize it with the current time
including microseconds, the default __construct() did not show a sign of
microsecond suppport. Changing this behaviour 7 years after introduction
cannot be called a bugfix (is this going into 5.6 and 7.0 as well?),
it's just a feature.
Did you ever Googled "microsecond site:php.net/manual"?
Only the documentation (comments not included) about createFromFormat
mentions 'microsecond'.
Making the assumption DateTime supports microtime would only be based on
internal, non-documented details. THAT would be a bad assumption.
See https://3v4l.org/aCRU0 and https://3v4l.org/4Oid8
[PHP: 7.0.13-dev ] derick@whisky:~/dev/php/php-src.git $ cat doo2.php
<?php
$date = new DateTimeImmutable( "13:39:04.123456" );
var_dump( $date );
?>
[PHP: 7.0.13-dev ] derick@whisky:~/dev/php/php-src.git $ php -n
doo2.php
object(DateTimeImmutable)#1 (3) {
["date"]=>
string(26) "2016-11-08 13:39:04.123456"
["timezone_type"]=>
int(3)
["timezone"]=>
string(3) "UTC"
}
We could set microseconds to 0, which is cumbersome because of a
missing setMicroseconds method. One needs to call setTime with
retrieved hours, minutes, seconds or setTimestamp($dt->format('U'))...
As you're overloading the DateTime class anyway, that's merely a minor
inconvenience.
cheers,
Derick
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