[wp-trac] [WordPress Trac] #39210: switch_to_locale() unloads all plugin and theme translations

[WordPress Trac]

#39210: switch_to_locale() unloads all plugin and theme translations
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 Reporter:  gchtr         |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  I18N          |     Version:  4.7
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:
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Changes (by ocean90):

 * keywords:   => needs-patch


Comment:

 Hello @gchtr, welcome to WordPress Trac!

 Thanks for your detailed report!
 The language switcher was introduced in [38961]. The first iterations had
 support for caching translations during a switch, see
 [attachment:26511.diff:ticket:26511]. But this was removed in favour of
 `_load_textdomain_just_in_time()`. The committed version had also a change
 [https://core.trac.wordpress.org/changeset/38961#file9 to the POMO
 library] to store the current path of a translation file. But the part in
 the switcher didn't actually work and got removed in
 [https://core.trac.wordpress.org/changeset/39330/trunk/src/wp-includes
 /class-wp-locale-switcher.php 39330]. So yeah, you're right that the
 switcher can't handle translations by themes/plugins which don't have
 their translations in `WP_LANG_DIR` which is used by
 `_load_textdomain_just_in_time()`.

 Sadly we didn't document that in the dev note. It's not really intended
 behavior, but it's the current behavior. As a workaround you can use the
 new [https://developer.wordpress.org/reference/hooks/change_locale/
 change_locale] action. It gets called when a locale is switched or
 restored. You can use it to call your custom
 `load_(theme|plugin)_textdomain()` function.

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Ticket URL: <https://core.trac.wordpress.org/ticket/39210#comment:1>
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