[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
--------------------------+------------------------------
 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:
--------------------------+------------------------------

Comment (by gchtr):

 Thanks for the explanation @ocean90! I see that for performance reasons,
 it makes total sense to do it like that.

 I now use the following workaround, which works fine:

 {{{#!php
 <?php
 add_action( 'change_locale', 'force_load_theme_textdomain' );

 // Switch to site locale
 $site_locale = get_locale();
 $locale_switched = switch_to_locale( $site_locale );
 }}}

 {{{#!php
 <?php
 /**
  * Hotfix for WordPress 4.7
  *
  * WordPress removes translations when switch_to_locale is used in
 backend.
  * Until this error is resolved, we circumvent it by adding a filter
  * to force the site locale for load_theme_textdomain() and then load the
 missing
  * text domain.
  *
  * @see https://core.trac.wordpress.org/ticket/39210
  */
 function force_load_theme_textdomain() {
     add_filter( 'theme_locale', 'force_site_locale_once' );
     load_theme_textdomain( 'axa-blog', get_template_directory() .
 '/languages' );
 }

 /**
  * Forces site locale once.
  *
  * Since 4.7 WordPress always returns the user locale in the backend.
  * This filters tells WordPress to use the site locale once when
  * load_theme_textdomain() is used.
  *
  * @return string   $locale The locale to use.
  */
 function force_site_locale_once() {
     // Remove filter to use it only once
     remove_filter( 'theme_locale', 'force_site_locale_once' );

     // Return site locale
     return get_locale();
 }
 }}}

 I have to use another filter before using `load_theme_textdomain` to
 force-load the site’s text domain and not the user’s, which is the default
 for the backend.

 Now is it really a bug or a matter of documentation (the special case of
 using switch_to_locale() in the backend)? Am I on an edge case here? Or
 should this be made more convenient for developers?

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Ticket URL: <https://core.trac.wordpress.org/ticket/39210#comment:3>
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