[wp-trac] [WordPress Trac] #49807: load_plugin_textdomain() expects a path relative to plugins/, making i18n for mu-plugins difficult

[WordPress Trac]

#49807: load_plugin_textdomain() expects a path relative to plugins/, making i18n
for mu-plugins difficult
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 Reporter:  theMikeD      |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  I18N          |    Version:
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Looking though the code for `load_plugin_textdomain()`
 (https://core.trac.wordpress.org/browser/tags/5.4/src/wp-
 includes/l10n.php#L797) I can see that it is expecting to receive a path
 relative to the plugins folder, as defined by `WP_PLUGIN_DIR`.

 All fine as long as the plugin is located within the folder defined by
 `WP_PLUGIN_DIR`...but mu-plugins are not; they are typically in a folder
 parallel to `WP_PLUGIN_DIR` but they can be anywhere via the
 `WPMU_PLUGIN_DIR` define.

 This makes it very difficult to add a text domain to a mu-plugin, since
 the only way I have so far found is to pass a relative folder, such as
 `../mu-plugins/plugin-folder/languages`, which is problematic because it's
 making assumptions about the setup.

 Together with the apparently missing easy way to determine if a plugin is
 loaded normally or as part of the must-use loader, it's impossible to
 write `load_plugin_textdomain()` in a generic way that accounts for mu-
 plugins.

 The solution would seem to be to un-deprecate the second argument, but I'm
 not aware of the discussion around why it was removed.

 I hope someone can point out something easy I have overlooked!

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Ticket URL: <https://core.trac.wordpress.org/ticket/49807>
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