List item separator should be a WP_Locale property

[SergeyBiryukov]

Currently, some (most?) themes have a translatable list item separator for displaying a list of categories or tags. See an example in Twenty Seventeen​:

/* translators: used between list items, there is a space after the comma */
$separate_meta = __( ', ', 'twentyseventeen' );

One of ru_RU translation team contributors made a point that list item separator is a locale property, and it doesn't make much sense to translate it separately in multiple projects.

We could probably add it as a property of WP_Locale class, in addition to ::number_format['thousands_sep'] and ::number_format['decimal_point'], and there should be a public function like number_format_i18n(), e.g. get_list_item_separator(), for plugins and themes to use. Thoughts?

[swissspidy]

Sounds useful. Besides the default themes there are three instances of __( ', ' ) being used in core. Perhaps more when counting instances of implode( ', ', … ) that could make use of a translatable list item separator.

[rsiddharth]

Initial version (2021091800)

[rsiddharth]

@swissspidy @SergeyBiryukov I've uploaded the initial version of the patch.

Are you able to tell if I'm going in the correct direction?

[johnbillion]

Just noting that I don't think it will be possible to change the default themes to use this new method because they need to remain compatible with the version of WordPress where they were introduced. A compatibility layer in each theme could be an option.

[SergeyBiryukov]

Thanks for the patch! The WP_Locale part looks good at a glance.

For the usage though, I think we'd want to avoid using the $wp_locale global in all those instances, and just wrap this in a function like wp_get_list_item_separator() that would still call $wp_locale->get_list_item_separator() internally.

As noted above, we should also think about backward compatibility for bundled themes.

[rsiddharth]

Version 2021092000

[rsiddharth]

@johnbillion @SergeyBiryukov I uploaded the second version of the patch.

Changes:

• Added wrapper function -- wp_get_list_item_separator() -- for WP_Locale::get_list_item_separator.
• Replaced $wp_locale->get_list_item_separator() calls with wp_get_list_item_separator() calls.
• Added a "compatibility layer" for the twentyeleven theme. Does that look correct?

Trac ticket: https://core.trac.wordpress.org/ticket/39733

[audrasjb]

The above PR refreshes the previous patch against trunk and updates @since mentions. It also add again a removed translator comment.

[audrasjb]

The patch works fine on my side using default themes or navigating through admin screens.
Self assigning for commit consideration.

[audrasjb]

After patch: separator works on WP-Admin

[audrasjb]

After patch: separator works on front-end (example: Twenty Thirteen)

[audrasjb]

Manual tests are going well. Marking for commit.

[audrasjb]

In 52929:

i18n: Define List item separator as a WP_Locale property.

The list item separator is a locale property, and it doesn't make much sense to translate it separately in multiple projects. This changeset implements the following modifications:

• Define list item separator as a new WP_Locale property
• Add wp_get_list_item_separator() as a wrapper for WP_Locale::get_list_item_separator
• Replace $wp_locale->get_list_item_separator() calls with wp_get_list_item_separator()
• Added a compatibility layer for bundled themes

Props SergeyBiryukov, swissspidy, rsiddharth, johnbillion, audrasjb.
Fixes #39733.

[audrasjb]

This change deserves a dev note or at least a mention in the Misc changes dev note.

Committed in https://core.trac.wordpress.org/changeset/52929

[SergeyBiryukov]

In 52933:

I18N: Move wp_get_list_item_separator() to a more appropriate place.

Follow-up to [52929].

See #39733.