Upgrading from 1.2.6 to 1.3 disables site

[wpmuguru]

In my test environment, it only happened on the front end but anyone running a theme or plugin that uses a BP function across the WP admin area will have a disabled site when they upgrade.

The error I got was call to undefined function bp_...

A use case where this would happen is a theme that modifies the admin bar by adding or removing links.

The test I use to determine if BP is active is whether the constant BP_VERSION is defined. The bp_loaded, bp_init, bp_include hooks per ​http://codex.buddypress.org/plugin-development/checking-buddypress-is-active/ are not accessible to themes because those hooks fire before the theme is loaded.

[wpmuguru]

BP_VERSION isn't used in the upgrade script.

[DJPaul]

I may be misunderstanding, but can't a theme's functions.php hook into one of those actions and do its thing there?

This is also sort of related to #2789

[wpmuguru]

Replying to DJPaul:

I may be misunderstanding, but can't a theme's functions.php hook into one of those actions and do its thing there?

No, plugins_loaded is fired before the theme functions.php is loaded by WP.

​https://core.trac.wordpress.org/browser/trunk/wp-settings.php#L204

​https://core.trac.wordpress.org/browser/trunk/wp-settings.php#L279

[DJPaul]

Since this ticket, effort has been put in to make sure that we don't kill sites after a new version of BuddyPress is installed but before the update scripts are run.