Hey Rasmus,
> On 19 Jan 2015, at 04:52, Rasmus Lerdorf <[email protected]> wrote:
>
>> On 01/18/2015 02:08 PM, Rasmus Lerdorf wrote:
>> We have to be really really careful with this "oh, that code is wrong,
>> so we can break it argument". This will break hundreds if not thousands
>> of sites in a hard-to-debug way. It took me less than a minute of
>> looking on Github to find a case that will break:
>>
>> https://github.com/chenboking/service.downloadmanager.amule/blob/cda510415f9a58660e096a7de42b3ea6f39ee851/webserver/php-default/amuleweb-main-search.php#L121
>>
>> It is extremely common to just do a less-than or a greater-than check in
>> a user comparison function. Of course it isn't textbook-correct, but
>> since it has always worked, people do it.
>
> And just to further illustrate this, I just downloaded the current
> Wordpress release and sure enough, Wordpress would also be broken by
> this change.
>
> In http://core.svn.wordpress.org/trunk/wp-includes/class-simplepie.php
> look at the sort_items() method:
>
> /**
> * Sorting callback for items
> *
> * @access private
> * @param SimplePie $a
> * @param SimplePie $b
> * @return boolean
> */
> public static function sort_items($a, $b)
> {
> return $a->get_date('U') <= $b->get_date('U');
> }
>
> I am not saying we should revert the change, but we need to be very
> aware of the effect this change will have on PHP7 adoption. The really
> nasty part is that even if a big codebase has unit tests covering the
> code, unless the unit test actually tests an array with more than 16
> elements, all tests will pass and the application will only fail in
> production with production data. And there are no errors or warnings of
> any sort either that will help people track this down.
>
> This will need to be front and center in the UPGRADING doc with an
> explanation about how to write a proper ordering function.
Related: since we have no Perl-like spaceship operator ($a <=> $b), writing comparison
functions is unnecessarily complex in the common case, as you must produce -1, 0, 1 yourself.
Could we expose a cmp() or compare() function that calls our internal comparison operator? This
would make writing custom sort functions a lot nicer, and quite possibly improve some other kinds of
code.
That would also mean a future sorting API could unify user sorts and non-user sorts: just make the
default callback be cmp().
Usage would be like this:
cmp(1, 2); // 1
cmp(1, 1); // 0
cmp(2, 1); // 1
Essentially, exactly like the spaceship in Perl, but a function.
Thoughts?
--
Andrea Faulds
http://ajf.me/