Misleading PHPdoc for filter {$adjacent}_post_link

[apermo]

The documentation for the filter {$adjacent}_post_link inside /wp-includes/link-template.php suggests that $post is a WP_Post.
The function get_adjacent_post() though will deliver an empty string if there is no adjacent post.

It is arguable if get_adjacent_post() shouldn't return null in that case, but nevertheless, in it's current state, the PHPdoc for the filter is misleading. If one uses these for typehinting, a fatal error will be thrown.

I've attached a patch, with my suggestion for an updated PHPdoc.

[apermo]

Patch of the PHPdoc.

[audrasjb]

Hello, thanks for the ticket and for the related patch,

Maybe we could use a similar wording than the one used in the get_adjacent_post() function?
Empty string if no corresponding post exists.

Updating the Version tag to 4.2 as this filter was added in this version.

[apermo]

I'm fine with any wording, as long, as the type is updated to WP_Post|string.

And thanks for the quick response.

[SergeyBiryukov]

In 54841:

Docs: Correct type for the $post parameter of the {$adjacent}_post_link filter.

The parameter was documented as WP_Post, but it contains the value of get_adjacent_post(), which returns an empty string if there is no corresponding post, so the correct type is WP_Post|string.

Follow-up to [11243], [16951], [28111], [32606].

Props apermo, audrasjb.
Fixes #57047.