get_sample_permalink unsets $post->filter even though this is a public property.

[herregroen]

The property should be set to null rather than being unset.

Unsetting it removes it entirely which means if it's later requested ( such as in WP_Post::__get ) this causes a notice to be thrown that the property doesn't exist.

[herregroen]

Added an alternative patch which restores the original filter.

[hellofromTonya]

Hello @herregroen,

Welcome back to WordPress Core's Trac! Thanks for opening this ticket :)

The unset( $post->filter ) was introduced in #8526 [10213].

Here's an example in action ​https://3v4l.org/66Nvl.

• In < PHP 8, it throws a Notice: Undefined property: WP_Post::$filter.
• In PHP 8, it throws a Warning: Undefined property: WP_Post::$filter.

Moving this ticket into 6.0.

[hellofromTonya]

#54735 was marked as a duplicate.

[hellofromTonya]

Assigning to me for review and unit tests.

https://core.trac.wordpress.org/ticket/54736

[peterwilsoncc]

I've created an initial patch in the linked pull request:

• The original filter value is stored early in the function
• This value is then restored after been replaced with sample

In [53042] it was ensured that the filter was always set in post objects, this is why I am restoring it rather than nulling it.

No tests at present but feel free to push them to the branch on my repo.

[niravsherasiya7707]

Hello @peterwilsoncc & @hellofromTonya can I start writing PHPUnit test for the changes made on this PR(​https://github.com/WordPress/wordpress-develop/pull/2626).

[hellofromTonya]

With 6.0 RC1 tomorrow and this issue not introduced in the 6.0 cycle, moving this ticket and ongoing work to 6.1.

[ironprogrammer]

@niravsherasiya7707: Absolutely! As Peter mentioned, you could submit unit tests through a PR to ​Peter's branch, or fork ​PR 2626 directly and add the tests to your own branch.

Props will pick up Peter's original PR, but if you end up forking the original, it's always nice to mention where it started 🙌🏻

[Rahmohn]

@peterwilsoncc I've created a PR adding tests: ​https://github.com/peterwilsoncc/wordpress-develop/pull/9

Other than that, it's necessary to fix a ​typo

[peterwilsoncc]

In 54244:

Posts, Post types: Prevent get_sample_permalink() modifying the post object.

get_sample_permalink() (ab)uses the $post->filter property to indicate a sample permalink is being generated for the post. This change ensures the property is restored to its original value.

Props herregroen, hellofromTonya, peterwilsoncc, Rahmohn, costdev.
Fixes #54736.

Merged in https://core.trac.wordpress.org/changeset/54244 / ​https://github.com/WordPress/wordpress-develop/commit/4241aa348a7e4b174572aab4a204419b8423e13f