Notice for _load_textdomain_just_in_time despite correct use of init hook

[markhowellsmead]

The notice “Notice: Function _load_textdomain_just_in_time was called incorrectly. Translation loading for the pt-must-use domain was triggered too early. This is usually an indicator for some code in the plugin or theme running too early. Translations should be loaded at the init action or later.” is being thrown in a private plugin. The call to load_plugin_text_domain is as follows.

function ptMustUseTranslations()
{
	load_plugin_textdomain('pt-must-use', false, __DIR__ . '/languages');
}
add_action('init', 'ptMustUseTranslations');

[swissspidy]

This code alone does not trigger this notice.

You are probably calling __() somewhere else in your mu-plugin earlier than init. As per ​https://make.wordpress.org/core/2024/10/21/i18n-improvements-6-7/, tools like Query Monitor are a snippet like the following one can help you pinpoint the exact location:

add_action(
	'doing_it_wrong_run',
	static function ( $function_name ) {
		if ( '_load_textdomain_just_in_time' === $function_name ) {
			debug_print_backtrace();
		}
	}
);

[markhowellsmead]

That code never ran, so I guess that the notice was being generated before the actions were fired. I traced it back to a call to get_plugin_data being called on a class constructor; presumably, therefore, too early.

[swissspidy]

The get_plugin_data() case is covered in that blog post I linked to as well. Setting the translate parameter to false is an easy fix that should suffice in most cases.