Using "__" in a plugin's main file, outside of an action callback prevents post saving in the editor.

[kmgalanakis]

When trying to save a post in the new editor (Gutenberg), the saving fails if there is an activated plugin that uses __ outside of a callback action.

I managed to reproduce the issue by creating a test-plugin using the wp scaffold plugin test-plugin. Then, in the main file of the plugin, I added $test = __( 'test', 'my-plugin' ).

After activating the plugin, the post saving stopped working. The saving is done through the REST API and the code from my plugin is loaded as well, but is_user_logged_in is not registered at that point, which gives me the following fatal error.

[30-Oct-2018 13:17:04 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function is_user_logged_in() in /srv/www/xxxxxx/public_html/wp-includes/l10n.php:137
Stack trace:
#0 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(1051): determine_locale()
#1 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(1013): _get_path_to_translation_from_lang_dir('test-plugin')
#2 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(983): _get_path_to_translation('test-plugin')
#3 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(1081): _load_textdomain_just_in_time('test-plugin')
#4 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(170): get_translations_for_domain('test-plugin')
#5 /srv/www/xxxxxx/public_html/wp-includes/l10n.php(250): translate('test', 'test-plugin')
#6 /srv/www/xxxxxx/public_html/wp-content/plugins/test-plugin/test-plugin.php(27): __('test', 'test-plugin')
#7 /srv/www/xxxxxx/public_html/wp-settings.php(322): include_once('/srv/www/xxxxxx/...')
#8 /srv/www/xxxxxx/public_html/wp-config.php(81): require_once('/srv/www/xxxxxx/...')
#9 /srv/www/xxxxxx/public_html/wp-lo in /srv/www/xxxxxx/public_html/wp-includes/l10n.php on line 137

[swissspidy]

Sounds like a duplicate of #43869 to me.

It's not editor related though. You just happen to use a function way too early because you execute something straight away before WordPress has fully loaded. What are you trying to achieve that can't be done by hooking into init or something?

[kmgalanakis]

Mine was I test plugin that I prepared for something else and I happened to see that issue. The strange thing is that this test plugin was working nicely in WP 5.0-beta1.

Whatever changed in WP 5.0-beta2 and broke my plugin will surely break other plugins as well.

[Chouby]

@swissspidy This issue is probably quite severe. WooCommerce or ACF prevent a post to be saved with this same error.

[joshf]

@Chouby You're correct. ACF 5.7.7 on an otherwise vanilla 5.0-beta2 installation triggers a fatal error when attempting to save a post.

[30-Oct-2018 21:25:23 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function is_user_logged_in() in /Users/sb05/sites/wp-beta2/wp-includes/l10n.php:137
Stack trace:
#0 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(1051): determine_locale()
#1 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(1013): _get_path_to_translation_from_lang_dir('acf')
#2 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(983): _get_path_to_translation('acf')
#3 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(1081): _load_textdomain_just_in_time('acf')
#4 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(170): get_translations_for_domain('acf')
#5 /Users/sb05/sites/wp-beta2/wp-includes/l10n.php(250): translate('Advanced Custom...', 'acf')
#6 /Users/sb05/sites/wp-beta2/wp-content/plugins/advanced-custom-fields-pro/acf.php(80): __('Advanced Custom...', 'acf')
#7 /Users/sb05/sites/wp-beta2/wp-content/plugins/advanced-custom-fields-pro/acf.php(690): ACF->initial in /Users/sb05/sites/wp-beta2/wp-includes/l10n.php on line 137

[danielbachhuber]

Thanks for the report, @kmgalanakis.

Closing in favor of #45235, which is a more precise reporting of the problem.