get_user_by() makes use of the cache even if it does not exists any longer

[hakre]

This is mostly an error report, and it's quite bloody. But I thought I better report it before it gets lost.

I ran over this while having the following error message:

Fatal error: Call to a member function get() on a non-object in wp-includes\cache.php on line 93

That is the following code:

function wp_cache_get($id, $flag = '') {
	global $wp_object_cache;

	return $wp_object_cache->get($id, $flag);
}

So this API function (!) is blindly using that global variable w/o even checking if it's that what it thinks it is. Well not only that this is dangerous with any global in this case, every other function that relies on the function like get_user_by() does exit with a fatal error. for example after the cache has been shut down.

[hakre]

More Info: In my case $GLOBALSwp_object_cache? is still set, but it's value is NULL.

[hakre]

My previous comment is wrong. Correction:

More Info: In my case $GLOBALS['wp_object_cache'] is not set any longer / NULL.

[wojtek.szkutnik]

Patch added. Using is_object and method_exists is as safe as it could get. I'm only wondering if there's any need to check if the method exists if $wp_object_cache is valid?

[hakre]

Under certain circumstance the defensive development approach is good. But I do not think that in wordpress defensive programming is common sense.

In this cache case for example, this will create overhead for 99.999% of all cases.

With my patch I approach the problem from the other side to offer plugin or core developers the possibility to check for cahce existance (for example on shutdowns or so).

[nacin]

get_user_by() is a pluggable function. Even if it were defined in mu-plugins and used immediately, the object cache should already be available. Can you provide steps to reproduce?