Add filter to validate_theme_requirements

[kraftbj]

There may be the need to add extra requirements for a theme to validate that site administrators may want to add. The validate_theme_requirements function looks keen for this, but there are currently no hooks in the function.

An example use case: A particular site on a multisite should never have a theme changed via the UI (a mission-critical site). The multisite, generally, has various themes network activated. Such a filter could allow a site administrator to check the blog ID and return a WP_Error if the blog ID is in a "theme_change_disallowed" array.

Proposing a validate_theme_requirement filter that hooks at the end of the current function to allow additional validation requirements. Intentionally not filtering the current failing conditions (incompatible WP or PHP) to prevent poor implementation of the filter to lead to a PHP/WP version-related fatal.

Adds a filter, validate_theme_requirements, to allow for additional theme validation requirements.

Trac ticket: https://core.trac.wordpress.org/ticket/54381

[sachinrajcp123]

Enhancement: Add filter hook to allow customization of validate_theme_requirements() results.

[kraftbj]

Refreshed the patch to see if we can land in 6.9!

[wildworks]

This ticket was featured on today's 6.9 Bug Scrub.

Maybe @jorbin will take a look at this ticket if he has time.

[joedolson]

It really seems like we should add the same filtering capabilities in validate_plugin_requirements(), at the same time, which seems to have the same limitations.

For API consistency, add a filter to validate_plugin_requirement comparable to validate_theme_requirement

Not sure where tests for this might live, if we need them.

Trac ticket: https://core.trac.wordpress.org/ticket/54381

See ​https://github.com/WordPress/wordpress-develop/pull/1812

@joedolson good catch. I agree.

[jorbin]

In 60995:

Plugins and Themes: Add filters to validation functions.

It is now possible to add additional validation requirements for themes and plugins besides the built in core checks.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/1812 and ​https://github.com/WordPress/wordpress-develop/pull/10361.

Props kraftbj, mukesh27, jorbin, joedolson.
Fixes #54381.

[desrosj]

The miscellaneous developer-focused changes developer note mentioned the two new hooks introduced in [60995] but did not cover their usage in depth: ​https://make.wordpress.org/core/2025/11/17/miscellaneous-developer-focused-changes-in-6-9/.