[wp-trac] [WordPress Trac] #58896: Fix WP_List_Table magic methods for PHP 8.2 dynamic properties

[WordPress Trac]

#58896: Fix WP_List_Table magic methods for PHP 8.2 dynamic properties
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 Reporter:  antonvlasenko                        |       Owner:
                                                 |  hellofromTonya
     Type:  defect (bug)                         |      Status:  closed
 Priority:  normal                               |   Milestone:  6.4
Component:  Administration                       |     Version:  4.0
 Severity:  normal                               |  Resolution:  fixed
 Keywords:  php82 has-patch has-unit-tests       |     Focuses:  php-
  commit                                         |  compatibility
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Changes (by hellofromTonya):

 * status:  assigned => closed
 * resolution:   => fixed


Comment:

 In [changeset:"56349" 56349]:
 {{{
 #!CommitTicketReference repository="" revision="56349"
 Code Modernization: Deprecate dynamic properties in WP_List_Table magic
 methods.

 The unknown use of unknown dynamic property within the `WP_List_Table`
 property magic methods is now deprecated. A descriptive deprecation notice
 is provided to alert developers to declare the property on the child class
 extending `WP_List_Table`.

 Changes in this commit:
 * Adds a deprecation notice to the `__get()`, `__set()`, `__isset()`,
 `__unset()` magic methods, i.e. to alert and inform developers when
 attempting to get/set/isset/unset a dynamic property.
 * Fixes `__get()` to explicitly returns `null` when attempting to get a
 dynamic property.
 * Removes returning the value when setting a declared property, as (a)
 unnecessary and (b) `__set()` should return `void`
 [https://www.php.net/manual/en/language.oop5.overloading.php#object.set
 per the PHP handbook].
 * Adds unit tests for happy and unhappy paths.

 For backward compatibility, no changes are made to the internal declared
 properties listed in `$compat_fields` and accessed through the magic
 methods.

 For example:
 A child class uses a property named `$data` that is not declared / defined
 as a property on the child class. When getting its value, e.g.
 `$list_table->data`, the `WP_List_Table::__get()` magic method is invoked,
 the following deprecation notice thrown, and `null` returned:

 >The property `data` is not defined. Setting a dynamic (undefined)
 property is deprecated since version 6.4.0! Instead, define the property
 on the class.

 === Why not remove the magic methods, remove the `$compat_fields`
 property, and restore the properties `public`?

 tl;dr Backward compatibility.

 Several plugins, one of which has over 5M installs, add a property to the
 `$compat_fields` array. Removing the property would cause an `Undefined
 property` `Warning` (PHP 8) | `Notice` (PHP 7) to be thrown. Removing the
 associated code would change the functionality.

 === Why not limit the deprecation for PHP versions >= 8.2?

 tl;dr original design intent and inform

 The magic methods and `$compat_fields` property were added for one
 purpose: to continue providing external access to internal properties
 declared on `WP_List_Table`. They were not intended to be used for dynamic
 properties.

 Deprecating that unintended usage both alerts developers a change is
 needed in their child class and informs them what to change.

 References:
 * Dynamic (non-explicitly declared) properties are deprecated as of PHP
 8.2 and are expected to become a fatal error in PHP 9.0.
 * A [https://www.youtube.com/live/vDZWepDQQVE?feature=share&t=10097 live
 open public working session] where these changes were discussed and agreed
 to.
 * [https://wiki.php.net/rfc/deprecate_dynamic_properties PHP RFC:
 Deprecate dynamic properties.]

 Related to #14579, #22234, #30891.

 Follow-up to [15491], [28493], [28521], [28524], [31146].

 Props antonvlasenko, jrf, markjaquith, hellofromTonya, SergeyBiryukov,
 desrosj, peterwilsoncc, audrasjb, costdev, oglekler, jeffpaul.
 Fixes #58896.
 See #56034.
 }}}

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/58896#comment:23>
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