Add warnings if loading translations too early

[swissspidy]

In my quick local testing I already identified a few plugins doing load_plugin_textdomain() wrong:

• [ ] RTL Tester
  • Not really maintained anymore anyway
• [x] Two Factor
  • https://github.com/WordPress/two-factor/pull/608
• [x] Elementor
  • https://github.com/elementor/elementor/pull/27200
• [ ] Litespeed Cache
  • https://github.com/litespeedtech/lscache_wp/pull/738

Plugins doing just-in-time loading wrong:

• [x] WooCommerce
  • https://github.com/woocommerce/woocommerce/pull/47113
• [ ] BuddyPress
  • Their theme integration also causes Twenty Twenty-Four translations to be loaded too early

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To-do:

• Improve wording for the _load_textdomain_just_in_time case, mentioning that it's typically caused by unintended side effects in a plugin or theme.
• What about themes? They usually do stuff in after_setup_theme, which runs right before init and current user setup. Probably all classic themes will be affected by this.

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Strangely, when one of these plugins and Query Monitor is active, there is some sort of infinite loop happening and the site crashes with a 500. @johnbillion Any thoughts why QM might run in circles here?

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Trac ticket: https://core.trac.wordpress.org/ticket/44937

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[johnbillion]

I'll take a look at what's happening in QM. I would recommend testing this out with some multilingual plugins if you haven't already. In particular WPML (and add-on plugins for it) has been a bit of a pain in the past with regard to loading translations too early.

[johnbillion]

I'm not seeing an infinite loop in my local testing with RTL Tester. I am concerned about calling __() from within the load textdomain functions though. Do we do that anywhere else?

[swissspidy]

OK here's how to reproduce the error. Even if you can't reproduce it so far, it seems logical:

1. Set user profile to something else than en_US
2. Activate RTL Tester
3. Activate Query Monitor
4. RTL Tester triggers the _doing_it_wrong in load_plugin_textdomain()
5. This calls QM_Collector_Doing_It_Wrong::action_doing_it_wrong_run() which uses __()
6. This in turn triggers the _doing_it_wrong in _load_textdomain_just_in_time()
7. This calls QM_Collector_Doing_It_Wrong::action_doing_it_wrong_run() again...

Adding some caching to only warn about a specific text domain once would solve this. Like a _doing_it_wrong_once function or so.

I am concerned about calling __() from within the load textdomain functions though. Do we do that anywhere else?

I don't think so. In theory it shouldn't cause any issues as the __() call and the load_*_textdomain() call use different domains. And the QM issue is only because it taps into the _doing_it_wrong.

[swissspidy]

Actually, it's more like QM would need to somehow unhook QM_Collector_Doing_It_Wrong in itself because it is triggering _doing_it_wrong itself.

[johnbillion]

Good spot, thanks. Temporarily unhooking itself is probably best otherwise there's no way to know what else might trigger a _doing_it_wrong call within any of the functions that are called from a doing it wrong handler.

[swissspidy]

Looking into warnings emitted by themes, such as twentytwentyone.

Some observations:

• Themes usually trigger just-in-time loading on after_setup_theme
• In the admin, the current user is set up right after setup_theme because of the load_default_textdomain() call in wp-settings.php
• Checking for after_setup_theme to emit a warning might be a better solution

I am concerned about calling __() from within the load textdomain functions though.

At this point determine_locale() will already have been called, and the current user thus setup. So I don't see any other side effect happening because of this.

[swissspidy]

@ocean90 @SergeyBiryukov @johnbillion Is this something one of you could provide feedback on? I think it's a nice safeguard that could still land before the beta, but it also might be a bit noisy.

[johnbillion]

This could be noisy but it might be interesting to see if any feedback about that is raised during beta.

[swissspidy]

Committed in https://core.trac.wordpress.org/changeset/59127