Pass $locale to override_load_textdomain filter

[ocean90]

In [53874] the $locale parameter was added to load_textdomain() so it can be used to properly fill WP_Textdomain_Registry.
Since the $locale may not be the same value as determine_locale() returns (e.g. when filtered by plugin_locale in load_plugin_textdomain()) we should also pass the new parameter to the filter so custom file loading implementations are using the same locale as load_textdomain() got.

In [53874] the $locale parameter was added to load_textdomain() so it can be used to properly fill WP_Textdomain_Registry.

Since the $locale may not be the same value as determine_locale() returns (e.g. when filtered by plugin_locale in load_plugin_textdomain()) we should also pass the new parameter to the filter so custom file loading implementations are using the same locale as load_textdomain() got.

Trac ticket: https://core.trac.wordpress.org/ticket/57056

[cadic]

Added a PR for this

[JeffPaul]

Adding to 6.2 milestone as initial PR updated from some code review feedback, needs final testing before readying for commit.

Would it make sense to move the locale detection earlier in the function, so that it's always passed as a string to the filter, instead of string|null?

if ( ! $locale ) {
	$locale = determine_locale();
}

IIRC that get_locale() call is deliberately as late as possible to avoid too many calls for performsnce reasons.

[costdev]

This ticket was discussed during the recent bug scrub. As all feedback on the PR has been addressed, I'm removing the changes-requested keyword.

[costdev]

This ticket was discussed during the bug scrub. As the patch only adds a new parameter to a filter, this should not need testing. Adding for commit consideration.

[audrasjb]

In 55196:

I18N: Pass $locale parameter to override_load_textdomain filter.

In [53874] the $locale parameter was added to load_textdomain() so it can be used to properly fill WP_Textdomain_Registry. Since $locale may not be the same value as determine_locale() returns (e.g. when filtered by plugin_locale in load_plugin_textdomain()) this changeset also passes the $locale parameter to the filter so custom file loading implementations are using the same locale as load_textdomain() got.

Follow-up to [53874].

Props ocean90, cadic, SergeyBiryukov, swissspidy, costdev.
Fixes #57056.

committed in https://core.trac.wordpress.org/changeset/55196