Not working properly when processed with wp-cli cron

Thanks for making a lean and effective caching plugin. I’ve recently discovered an issue, though.

This stems from “Clear all cache files when a post or page is published or updated” not working when using WP-CLI to run the WordPress cron instead of the web request method. But it probably has broader implications as well.

The variable $wp_cache_clear_on_post_edit is intended to be global, but it is not when run from the WP-CLI. This is because WP-CLI loads WordPress from inside a function, so if a variable is not explicitly declared as global, it is not global in that context. See: https://github.com/wp-cli/wp-cli/issues/4019. Since the variable effectively evaluates to false in this context, the option mentioned above does not work.

We are getting around this issue by placing global $wp_cache_clear_on_post_edit; inside an mu-plugin. This works because it runs before WP Super Cache, so it preemptively declares it as global.

I imagine there may be other variables that are intended to be global that don’t work within the WP-CLI context, but this is the one that has been causing us issues since our move to running cron with WP-CLI.