[wp-trac] [WordPress Trac] #56033: PHP 8.2: explicitly declare all known properties

[WordPress Trac]

#56033: PHP 8.2: explicitly declare all known properties
-----------------------------+---------------------
 Reporter:  jrf              |       Owner:  (none)
     Type:  task (blessed)   |      Status:  new
 Priority:  normal           |   Milestone:  6.1
Component:  General          |     Version:
 Severity:  normal           |  Resolution:
 Keywords:  has-patch php82  |     Focuses:
-----------------------------+---------------------
Description changed by jrf:

Old description:

> Dynamic (non-explicitly declared) properties are deprecated as of PHP 8.2
> and are expected to become a fatal error in PHP 9.0, though this last
> part is not 100% certain yet.
>
> RFC: https://wiki.php.net/rfc/deprecate_dynamic_properties
>
> **This ticket is intended ONLY for category 1 and 2 (see below), where
> fixing a typo or explicitly declaring the property fixes things.**
>
> == The problem
>
> === What is a dynamic property ?
>
> {{{#!php
> <?php
> class Foo {
>     public $id;
>
>     public function __construct( $id, $field_name ) {
>         // This is fine, the $id property exists on the class.
>         $this->id         = $id;
>
>         // This is a dynamically created property as the property
>         // is not declared on the class.
>         $this->field_name = $field_name;
>     }
> }
> }}}
>

> Dynamic properties can both be created from inside a class, like in the
> above example, as well as from outside the class (see the below example),
> which makes these issues very tricky to find via static analysis.
>
> {{{#!php
> <?php
> $obj = new Foo();
> $obj->type = 'something';
> }}}
>
> === When is something not a dynamic property ?
>
> 1. When the property is explicitly declared on the class.
> 2. When the property is explicitly declared on the (grand)parent class.
>

> === When are dynamic properties not problematic ?
>
> 1. When the class, or one of its parents, has a magic `__set()` method
> which assigns the property to a declared property.
> {{{#!php
> <?php
> class Foo {
>     private $fields = [];
>
>     public function __construct($field_name ) {
>         $this->field_name = $field_name; // Not problematic.
>     }
>
>     public function __set( $name, $value ) {
>         $this->fields[ $name ] = $value;
>     }
> }
> }}}
> 2. When the class, or its parent, extends the PHP native `stdClass`,
> which has highly optimized versions of the `__set()` magic method
> available.
>
> == Mitigation
>
> The solution needed depends on the specific situation and each instance
> where a deprecation is thrown needs to be individually evaluated.
>
> We can basically categorize dynamic properties into four base situations:
>
> || ||= Situation =||= Solution =||
> || 1. || Typo in property name || Fix the typo, either in the property as
> declared or where the property assignment happens ||
> || 2. || Known, named, dynamic property || Declare the property on the
> (parent) class ||
> || 3. || Known use of unknown dynamic properties || Declare the full set
> of magic methods on a class (preferred) or let the class extend
> `stdClass` (discouraged) ||
> || 4. || Unknown use of unknown dynamic properties || Use the
> `#[AllowDynamicProperties] attribute on the (parent) class and/or declare
> the full set of magic methods on a class and/or let the class extend
> `stdClass` ||
>
> Note: the `#[AllowDynamicProperties]` attribute is expected to be a
> temporary solution and it is expected that support for the attribute will
> be removed at some point in the future.
>
> == Patches
>
> **Reminder: This ticket is intended ONLY for patches which fall in
> category 1 and 2, where fixing a typo or explicitly declaring the
> property fixes things.**
>
> A full set of patches for all such ''known'' situations - based on
> running the WP test suite against PHP 8.2 - is available and PRs for each
> will be opened on GitHub with a link to this ticket.
>
> However, as the WP test suite does not cover the full code base, more
> instances of situations which fall under category 1 and 2 are expected to
> be discovered over time.
>
> Patches for any additional instances found, which fall under category 1
> or 2, can be uploaded to this ticket and this ticket should stay open for
> these kind of patches during the WordPress 6.1 release cycle.
>

> ----
>
> Related: #56009
>

> Trac ticket # is open for addressing dynamic properties in category 3 and
> 4.

New description:

 Dynamic (non-explicitly declared) properties are deprecated as of PHP 8.2
 and are expected to become a fatal error in PHP 9.0, though this last part
 is not 100% certain yet.

 RFC: https://wiki.php.net/rfc/deprecate_dynamic_properties

 **This ticket is intended ONLY for category 1 and 2 (see below), where
 fixing a typo or explicitly declaring the property fixes things.**

 == The problem

 === What is a dynamic property ?

 {{{#!php
 <?php
 class Foo {
     public $id;

     public function __construct( $id, $field_name ) {
         // This is fine, the $id property exists on the class.
         $this->id         = $id;

         // This is a dynamically created property as the property
         // is not declared on the class.
         $this->field_name = $field_name;
     }
 }
 }}}


 Dynamic properties can both be created from inside a class, like in the
 above example, as well as from outside the class (see the below example),
 which makes these issues very tricky to find via static analysis.

 {{{#!php
 <?php
 $obj = new Foo();
 $obj->type = 'something';
 }}}

 === When is something not a dynamic property ?

 1. When the property is explicitly declared on the class.
 2. When the property is explicitly declared on the (grand)parent class.


 === When are dynamic properties not problematic ?

 1. When the class, or one of its parents, has a magic `__set()` method
 which assigns the property to a declared property.
 {{{#!php
 <?php
 class Foo {
     private $fields = [];

     public function __construct($field_name ) {
         $this->field_name = $field_name; // Not problematic.
     }

     public function __set( $name, $value ) {
         $this->fields[ $name ] = $value;
     }
 }
 }}}
 2. When the class, or its parent, extends the PHP native `stdClass`, which
 has highly optimized versions of the `__set()` magic method available.

 == Mitigation

 The solution needed depends on the specific situation and each instance
 where a deprecation is thrown needs to be individually evaluated.

 We can basically categorize dynamic properties into four base situations:

 || ||= Situation =||= Solution =||
 || 1. || Typo in property name || Fix the typo, either in the property as
 declared or where the property assignment happens ||
 || 2. || Known, named, dynamic property || Declare the property on the
 (parent) class ||
 || 3. || Known use of unknown dynamic properties || Declare the full set
 of magic methods on a class (preferred) or let the class extend `stdClass`
 (discouraged) ||
 || 4. || Unknown use of unknown dynamic properties || Use the
 `#[AllowDynamicProperties] attribute on the (parent) class and/or declare
 the full set of magic methods on a class and/or let the class extend
 `stdClass` ||

 Note: the `#[AllowDynamicProperties]` attribute is expected to be a
 temporary solution and it is expected that support for the attribute will
 be removed at some point in the future.

 == Patches

 **Reminder: This ticket is intended ONLY for patches which fall in
 category 1 and 2, where fixing a typo or explicitly declaring the property
 fixes things.**

 A full set of patches for all such ''known'' situations - based on running
 the WP test suite against PHP 8.2 - is available and PRs for each will be
 opened on GitHub with a link to this ticket.

 However, as the WP test suite does not cover the full code base, more
 instances of situations which fall under category 1 and 2 are expected to
 be discovered over time.

 Patches for any additional instances found, which fall under category 1 or
 2, can be uploaded to this ticket and this ticket should stay open for
 these kind of patches during the WordPress 6.1 release cycle.


 ----

 Related: #56009


 Trac ticket #56034 is open for addressing dynamic properties in category 3
 and 4.

--

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/56033#comment:1>
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