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8.1 / Exception / Property Type / Backwards compatbility

php.internals

Philip Hofstetter

5 years ago

Hello

The following valid <= PHP 8.0 code that intends to make the $line property
public  is a fatal error in 8.1

class FooException extends Exception {
public $line;
}

However, the fixed code for 8.1:

class FooException extends Exception {
public int $line;
}

Is a fatal error in <= 8.0

Is there a way to create a class that makes the $line property public
that’s compatible with all versions of PHP without requiring conditional
declaration of the class?

For method return types, we have #[ReturnTypeWillChange], but for property
types 🤷‍♀️

Philip

Unnamed Person

5 years ago

Den 2021-08-10 kl. 11:55, skrev Philip Hofstetter:

> Hello
>
> The following valid <= PHP 8.0 code that intends to make the $line property
> public  is a fatal error in 8.1
>
> class FooException extends Exception {
>      public $line;
> }
>
> However, the fixed code for 8.1:
>
> class FooException extends Exception {
>      public int $line;
> }
>
> Is a fatal error in <= 8.0
>
> Is there a way to create a class that makes the $line property public
> that’s compatible with all versions of PHP without requiring conditional
> declaration of the class?
>
> For method return types, we have #[ReturnTypeWillChange], but for property
> types 🤷‍♀️
>
> Philip
>

Hi,

Has this been adressed / solved in some way and does it needs
to be fixed?

I mean we are approaching RC1.

r//Björn L

Dan Ackroyd

5 years ago

On Thu, 26 Aug 2021 at 12:42, Björn Larsson via internals
<internals@lists.php.net> wrote:

>
> Den 2021-08-10 kl. 11:55, skrev Philip Hofstetter:
> > The following valid <= PHP 8.0 code that intends to make the $line property
> > public  is a fatal error in 8.1

....

> >
> > For method return types, we have #[ReturnTypeWillChange], but for property
> > types 🤷‍♀️

> Hi,
>
> Has this been adressed / solved in some way and does it needs
> to be fixed?

My understanding is that the two scenarios are not the same and that
there isn't much enthusiasm for 'fixing' it.

For return types, the #[ReturnTypeWillChange] annotation is a
temporary work-around, and one that would be used by a lot of people.
It would only be used by a library until that library drops support
for older versions of PHP.

For the exception case, the way that (for legacy reasons) PHP supports
having a public property in a child class that "overwrites" (mostly)
the protected property in the parent class, is a pretty hinkey thing
to do, and so this is likely to only affect a small number of people.
It's not obvious to me how long a bridging annotation would need to
hang around for, and it's really not obvious what the exact details of
how it would work would be.

I'd suggest using a getter method, which would work on all relevant versions.

cheers
Dan
Ack

Ben Ramsey

5 years ago

Dan Ackroyd wrote on 8/26/21 09:43:

> On Thu, 26 Aug 2021 at 12:42, Björn Larsson via internals
> <internals@lists.php.net> wrote:
>>
>> Den 2021-08-10 kl. 11:55, skrev Philip Hofstetter:
>>> The following valid <= PHP 8.0 code that intends to make the $line property
>>> public  is a fatal error in 8.1
> ....
>>>
>>> For method return types, we have #[ReturnTypeWillChange], but for property
>>> types 🤷‍♀️
>
>> Hi,
>>
>> Has this been adressed / solved in some way and does it needs
>> to be fixed?
>
> My understanding is that the two scenarios are not the same and that
> there isn't much enthusiasm for 'fixing' it.
>
> For return types, the #[ReturnTypeWillChange] annotation is a
> temporary work-around, and one that would be used by a lot of people.
> It would only be used by a library until that library drops support
> for older versions of PHP.
>
> For the exception case, the way that (for legacy reasons) PHP supports
> having a public property in a child class that "overwrites" (mostly)
> the protected property in the parent class, is a pretty hinkey thing
> to do, and so this is likely to only affect a small number of people.
> It's not obvious to me how long a bridging annotation would need to
> hang around for, and it's really not obvious what the exact details of
> how it would work would be.
>
> I'd suggest using a getter method, which would work on all relevant versions.
>
> cheers
> Dan
> Ack
>

It's interesting to note that `$line` and `$file` both behave this way
in PHP 8.1, but `$code` and `$message` do not.

class Foo extends Exception
{
protected $code = 100;
protected $message = 'Hello';
protected $line = 45;
protected $file = '/path/to/file.php';
}

Cheers,
Ben

Nikita Popov

5 years ago

On Thu, Aug 26, 2021 at 4:43 PM Dan Ackroyd <Danack@basereality.com> wrote:

> On Thu, 26 Aug 2021 at 12:42, Björn Larsson via internals
> <internals@lists.php.net> wrote:
> >
> > Den 2021-08-10 kl. 11:55, skrev Philip Hofstetter:
> > > The following valid <= PHP 8.0 code that intends to make the $line
> property
> > > public  is a fatal error in 8.1
> ....
> > >
> > > For method return types, we have #[ReturnTypeWillChange], but for
> property
> > > types 🤷‍♀️
>
> > Hi,
> >
> > Has this been adressed / solved in some way and does it needs
> > to be fixed?
>
> My understanding is that the two scenarios are not the same and that
> there isn't much enthusiasm for 'fixing' it.
>
> For return types, the #[ReturnTypeWillChange] annotation is a
> temporary work-around, and one that would be used by a lot of people.
> It would only be used by a library until that library drops support
> for older versions of PHP.
>
> For the exception case, the way that (for legacy reasons) PHP supports
> having a public property in a child class that "overwrites" (mostly)
> the protected property in the parent class, is a pretty hinkey thing
> to do, and so this is likely to only affect a small number of people.
> It's not obvious to me how long a bridging annotation would need to
> hang around for, and it's really not obvious what the exact details of
> how it would work would be.
>
> I'd suggest using a getter method, which would work on all relevant
> versions.
>

Right. I at least do not plan to address this issue. If you take a
protected property and publicly re-export it, then any compatibility issues
are on you.

If you need to keep doing this for API stability reasons, then the way to
do it would be a conditional class declaration. Or to keep the scope
smaller, you can conditionally declare a trait with just the property  and
then use it inside a larger class.

Regards,
Nikita

Ben Ramsey

5 years ago

Nikita Popov wrote on 8/26/21 09:57:

> Right. I at least do not plan to address this issue. If you take a
> protected property and publicly re-export it, then any compatibility issues
> are on you.

This does not appear to affect only cases where one is re-exporting a
protected property as public.

Exception protected properties without type hints:

* PHP <= 8.0 - https://3v4l.org/GWmrk
* PHP 8.1 - https://3v4l.org/GWmrk/rfc


Exception protected properties with type hints:

* PHP <= 8.0 - https://3v4l.org/UX1Pa
* PHP 8.1 - https://3v4l.org/UX1Pa/rfc

Cheers,
Ben

Unnamed Person

5 years ago

Den 2021-08-26 kl. 20:34, skrev Ben Ramsey:

> Nikita Popov wrote on 8/26/21 09:57:
>> Right. I at least do not plan to address this issue. If you take a
>> protected property and publicly re-export it, then any compatibility issues
>> are on you.
>
> This does not appear to affect only cases where one is re-exporting a
> protected property as public.
>
> Exception protected properties without type hints:
>
> * PHP <= 8.0 - https://3v4l.org/GWmrk
> * PHP 8.1 - https://3v4l.org/GWmrk/rfc
>
>
> Exception protected properties with type hints:
>
> * PHP <= 8.0 - https://3v4l.org/UX1Pa
> * PHP 8.1 - https://3v4l.org/UX1Pa/rfc
>
> Cheers,
> Ben
>

So it looks like we have a bug here since the same code behaves
differently between 8.0 and 8.1.

I don't think it's obvoius that by adding a type hint we get
different behaviour for the "same" code in 8.0 vs 8.1.

The reason I brought this up is that in an Open source library
it's discussed how to solve this. Loading different versions of
the libray feels clunky.

r//Björn L

Ben Ramsey

5 years ago

Philip Hofstetter wrote on 8/10/21 04:55:

> Hello
>
> The following valid <= PHP 8.0 code that intends to make the $line property
> public  is a fatal error in 8.1
>
> class FooException extends Exception {
>     public $line;
> }
>
> However, the fixed code for 8.1:
>
> class FooException extends Exception {
>     public int $line;
> }
>
> Is a fatal error in <= 8.0
>
> Is there a way to create a class that makes the $line property public
> that’s compatible with all versions of PHP without requiring conditional
> declaration of the class?
>
> For method return types, we have #[ReturnTypeWillChange], but for property
> types 🤷‍♀️

This sounds like a bug. I don't see this reported yet in the bug
tracker. Please open an issue at https://bugs.php.net

Cheers,
Ben

Alexandru Pătrănescu

5 years ago

On Tue, Aug 10, 2021 at 12:55 PM Philip Hofstetter <
phofstetter@sensational.ch> wrote:

> Hello
>
> The following valid <= PHP 8.0 code that intends to make the $line property
> public  is a fatal error in 8.1
>
> class FooException extends Exception {
>     public $line;
> }
>
> However, the fixed code for 8.1:
>
> class FooException extends Exception {
>     public int $line;
> }
>
> Is a fatal error in <= 8.0
>
> Is there a way to create a class that makes the $line property public
> that’s compatible with all versions of PHP without requiring conditional
> declaration of the class?
>
>

Not sure exactly why you need to $line property public.
If you need to be able to read it, you can use __get.
If you also need to write it, as that also worked, you can also use __set.

So an example that offers the same interface/interaction possible would be:
https://3v4l.org/tHhEL#v8.0.9
https://3v4l.org/tHhEL/rfc#vgit.master

But of course, when you look at the object with reflection, or how var_dump
prints it, the property will still be protected.

Regards,
Alex