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Date: Mon, 31 Oct 2022 15:38:05 -0400
In-Reply-To: <94DC0839-E43B-4F3A-9105-8F3CB9D7BBC1@joshbruce.dev>
Cc: php internals <internals@lists.php.net>
To: Josh Bruce <josh@joshbruce.dev>
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Subject: Re: [PHP-DEV] [RFC][Discussion] Objects can be declared falsifiable
From: josh@joshbruce.dev (Josh Bruce)

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Hello Interntals,

Someone reached out to me outside of internals regarding the RFC I =
submitted on being able to declare objects falsifiable, so, I decided to =
update and re-enter the fray.

I=E2=80=99ve updated the references section as many of the RFCs that =
were under discussion at the time have since been implemented.

I still find myself in situations where having the capability would be =
beneficial. Specifically, I=E2=80=99m noticing with API responses where =
I want to pass the body received from a ResponseInterface the object can =
check itself. I currently use methods such as:

->isValid()
->isInvalid()
->toBool()

And similar - the isValid and isInvalid() methods are just aliases of =
toBool(), which speaks to the ability for adopters to make their =
interfaces compatible without breaking changes in their code.

In the case of a conditional - looks like this:

$obj =3D Object::init($response);
If ($obj->isValid()) {
    // do something with $obj
}

Or:

If (
    $obj =3D Object::init($response) and
    $obj->isValid()
) {
    // do something with $obj
}

Would like to be able to do something like:

If ($obj =3D Object::init($response)) {
    // do something with $obj
}

As of today, the last example is always true. You wouldn=E2=80=99t be =
able to create a guard clause for the negation:

If (
    $obj =3D Object::init($response) and
    $obj =3D=3D=3D false
) {
    // handle invalid object, which could include something like =
$obj->failed()
}

Cheers,
Josh

> On Sep 26, 2020, at 5:20 PM, Josh Bruce <josh@joshbruce.dev> wrote:
>=20
> Hey Internals,
>=20
> So, I received a message that said of the mail I should have received =
from internals bounced; so, this is part test and part update.
>=20
> I=E2=80=99ve started mapping out call paths in the project that =
brought this concept to light.
>=20
> The project, Shoop, never uses is_bool() - instead it always uses =
empty, then reverses that for:
>=20
> 1. Booleans
> 2. Numbers
> 3. Arrays
> 4. Strings
> 5. stdClass or data-only classes
> 6. Json strings, which it treats as #5
>=20
> I essentially get standard SPL behavior when I do this.
>=20
> For the object definition I can define two interfaces:
>=20
> 1. Falsifiable
> 2. Emptiable
>=20
> The checks go like this:
>=20
> 1. if the object implements Falsifiable: the __toBool method would be =
called and would return the result. (This check would be inside =
is_bool() and could use the empty() implementation)
> 2. if the object implements Emptiable: the __isempty method would be =
called and return the result. (This check would be inside empty())
> 3. else: standard output from is_bool() or empty() would be used when =
passing an instance to either of those SPL functions, depending on which =
the user is using.
>=20
> Because the concepts of emptiness and falsiness are so tightly =
coupled, I=E2=80=99m wondering if it would be better to implement both =
with this RFC??
>=20
> Otherwise, Emptiable would be a future enhancement consideration.
>=20
> I=E2=80=99d like to hear what the rest of Internals thinks.
>=20
> Next for me: I=E2=80=99m going to finish solidifying the Shoop project =
and make sure my other projects can use latest and then continue going =
through the tutorials from Nikita and others on doing development =
Internals.
>=20
> Cheers,
> Josh
>=20
>> On Aug 30, 2020, at 9:32 AM, Josh Bruce <josh@joshbruce.dev =
<mailto:josh@joshbruce.dev>> wrote:
>>=20
>> Hey Tyson,
>>=20
>> This is great! Thank you so much, sincerely.
>>=20
>> Still slow goings, which is fine, we have at least a year. lol
>>=20
>> Static analyzers seem to be the biggest concern to date.
>>=20
>> Haven=E2=80=99t been able to get one running locally - though I=E2=80=99=
ve only spent a few minutes here and there; definitely on the list.
>>=20
>> A use case for this sort of thing is also a concern or question. I =
came across Pipeline from the PHP League and saw their interruptible =
processor and was wondering if something like this would be helpful =
there - for pipeline patterns in general: =
https://github.com/thephpleague/pipeline/blob/master/src/InterruptibleProc=
essor.php
>>=20
>> While working on another project, saw this line from the PHP =
array_filter docs:
>>=20
>>     "If no callback is supplied, all entries of array equal to FALSE =
(see converting to boolean) will be removed."
>>=20
>> I=E2=80=99m still field testing the latest iteration of my base =
project, but wanted to put a working (non-internals) implementation out =
there (note this covers emptiness and falseness for the purposes of the =
project):
>>=20
>> Tests - =
https://github.com/8fold/php-shoop/blob/master/tests/RfcObjectCanBeDeclare=
dFalsifiableTest.php
>>=20
>> Interface - =
https://github.com/8fold/php-shoop/blob/master/src/FilterContracts/Interfa=
ces/Falsifiable.php - for our purposes the efToBool would be __toBool
>>=20
>> Default implementation - =
https://github.com/8fold/php-shoop/blob/master/src/Shooped.php#L216
>>=20
>> =E2=80=9CType system=E2=80=9D implementation - =
https://github.com/8fold/php-shoop/blob/master/src/Filter/TypeAsBoolean.ph=
p
>>=20
>> Cheers,
>> Josh
>>=20
>>> On Aug 9, 2020, at 3:59 PM, tyson andre <tysonandre775@hotmail.com =
<mailto:tysonandre775@hotmail.com>> wrote:
>>>=20
>>> Hi Josh,
>>>=20
>>> I'd recommend looking at https://github.com/php/php-src/pull/5156 =
(linked to in your RFC's reference) when implementing this PR.
>>> Additionally, I didn't see if this was brought up - PHP already has =
a class which is falsifiable - SimpleXMLElement.
>>>=20
>>> You can see the source of ext/simplexml/simplexml.c for `_IS_BOOL`
>>>=20
>>> ```
>>> static int sxe_object_cast_ex(zend_object *readobj, zval *writeobj, =
int type)
>>> {
>>> 	php_sxe_object *sxe;
>>> 	xmlChar        *contents =3D NULL;
>>> 	xmlNodePtr	    node;
>>> 	int rv;
>>>=20
>>> 	sxe =3D php_sxe_fetch_object(readobj);
>>>=20
>>> 	if (type =3D=3D _IS_BOOL) {
>>> 		node =3D php_sxe_get_first_node(sxe, NULL);
>>> 		if (node) {
>>> 			ZVAL_TRUE(writeobj);
>>> 		} else {
>>> 			ZVAL_BOOL(writeobj, =
!sxe_prop_is_empty(readobj));
>>> 		}
>>> 		return SUCCESS;
>>> 	}
>>> ```
>>>=20
>>> ```
>>> static php_sxe_object* php_sxe_object_new(zend_class_entry *ce, =
zend_function *fptr_count)
>>> 	intern->zo.handlers =3D &sxe_object_handlers;
>>> // ... elsewhere in ext/simplexml/simplexml.c
>>> 	sxe_object_handlers.cast_object =3D sxe_object_cast;
>>> ```
>>>=20
>>> The default handlers would be overridden, so this would probably =
need to fall back to the original handlers for types other than bool.
>>> Also, this might need to copy all of the handlers from the parent =
class entry's zend_object_handlers,
>>> to meet the expected behavior of other cast types and other magic =
behaviors from SimpleXMLElement and other classes continuing to work.
>>>=20
>>> =46rom the perspective of static analysis, a few things to note:
>>> - Static analyzers such as psalm/phan currently deliberately don't =
bother handling the possibility that `object` can be false even after it =
was checked for falsiness.
>>>  There's hundreds of other things that could be implemented, and =
adding the special casing and performance overhead checking for FFI =
objects and SimpleXMLElement, subclasses of those is currently low =
priority compared to those things.
>>>=20
>>>  Code using SimpleXMLElement/FFI is generally limited to a few files =
in practice.
>>>=20
>>>  Definitely possible for analyzers to support this for known base =
classes, though, and the priority would increase if the RFC passed.
>>>=20
>>>  I am a maintainer of Phan.
>>> - For BC reasons, internal data structures such as ArrayObject =
probably wouldn't get changed in any php release
>>>   (e.g. could break code using falsiness check instead of null =
check).
>>>   So this might lead to inconsistencies with newer extensions if =
half of the data structures treat emptiness as false and half don't.
>>> - This feature may end up getting adopted in cases where it's =
convenient but turns out prone to accidental bugs and later is =
deprecated and removed.
>>>  For example, =
https://stackoverflow.com/questions/25031236/if-elem-vs-elem-is-not-none =
was seen in python
>>>=20
>>>  (e.g. `if (!$this->resultSetObject) { $this->resultSetObject =3D =
slow_db_operation(); }`
>>>  would not behave the way people would previously expect for most =
objects (executed repeatedly instead of once))
>>>=20
>>> ```
>>> <?php
>>> function test(SimpleXMLElement $e) {
>>>    // False positive RedundantCondition in psalm
>>>    if ($e) {
>>>    }
>>> }
>>> ```=20
>>>=20
>>>> And I don=E2=80=99t know of a way to add an interface to new =
stdClass() - but thought this might be a valid use case:
>>>=20
>>> `stdClass` isn't a final class. I assume they meant this
>>>=20
>>> ```
>>> class EmptyStdClass extends stdClass implements Falsifiable {
>>>    public function __toBool() { return false; }
>>> }
>>> function example(stdClass $s) {
>>>    if (!$s) { throw new Exception("Previously impossible"); }
>>> }
>>> ```
>>>=20
>>> Thanks,
>>> - Tyson
>>> --
>>> PHP Internals - PHP Runtime Development Mailing List
>>> To unsubscribe, visit: https://www.php.net/unsub.php
>>>=20
>>=20
>=20


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