Add is_post_status_viewable filter

[peterwilsoncc]

Related to #49628.

Add a filter to the is_post_status_viewable() function to allow theme and plugin developers to override the default value.

In some circumstances a developer may require the checks use different conditions to the default.

[audrasjb]

Posts, Post Types: Introduce is_post_status_viewable hook to filter the result of the is_post_status_viewable() function.

[hellofromTonya]

Simplifies the strict boolean type check to conserve memory and processing.

[peterwilsoncc]

Functional changes in 54375.1.diff​ look good to me.

In 54375.2.diff​ I've added an explanation that the filter must return true, for the same reasons as discussed on #49628.

[hellofromTonya]

Explanation improvement in 54375.4.diff.

[hellofromTonya]

In 52043:

Posts/Post Types: Introduce 'is_post_status_viewable ' filter in is_post_status_viewable().

Introduces a new filter 'is_post_status_viewable' which allows overriding the check.

The function's return signature is a boolean type. This commit ensures
the return signature remains unchanged by requirinng a strict boolean
type of the returned filtered value.

Why?

• To maintain this signature and backwards-compatibility.
• To future prepare for PHP 8.1 and beyond.

An explanation is included in the filter's DocBlock.

Follow-up to [50130].

Props audrasjb, hellofromTonya, peterwilsoncc.
Fixes #54375.

[SergeyBiryukov]

It seems like this is a more common pattern in core to ensure a boolean return type from a filter:

return (bool) apply_filters( ... );

It's used in at least five other instances and appears to achieve the same goal. Is there a reason not follow that pattern here? Personally, I find it much easier to navigate the code later when similar things are done in a consistent way :)

The same applies to [52045].

[hellofromTonya]

@SergeyBiryukov See the explanation here as to why type casting is unpredictable and why a strict boolean check is used instead. Please note, strict boolean checks are also in Core. This types of checks are more future proof, predictable, and stable than type casting.

[SergeyBiryukov]

Replying to hellofromTonya:

See the explanation here as to why type casting is unpredictable and why a strict boolean check is used instead.

Thank you for pointing me to that discussion! Knowing the context helps a lot, I appreciate the explanation.

Re-closing this to keep the discussion in one place. Will comment on the other ticket once I have an informed opinion.

[audrasjb]

Dev note published: ​https://make.wordpress.org/core/2021/12/13/posts-post-types-and-taxonomy-changes-in-wordpress-5-9/