PHP Notice in get_cat_name()

[miqrogroove]

Notice: Trying to get property of non-object in /wp-includes/category.php on line 186

Can be triggered very easily by constructing a URL like /wp-admin/categories.php?action=delete&cat_ID=99999999999

[nacin]

Quick fix:
get_cat_name() should probably check to see if get_category() returns a wp_error, and if so, return (instead of returning ->name for a WP_Error). I'd suggest it passes along the error, but really, if you're asking for the cat name and the cat doesn't exist, you should get an empty string.

Real fix:
Like in wp-admin/comment.php for comments, wp-admin/categories.php should always first check if the category is legit before doing stuff to it. That would be something like if( is_wp_error( get_category($cat_ID) ) ) wp_die('No category with this ID.');

[sirzooro]

I think returning WP_Error is better than calling wp_die(), because in this case WP (directly or with plugin help) may return 404 to browser and/or display page "no category found".

[nacin]

Turns out it is only WP_Error when the taxonomy doesn't exist. get_category() will return such a WP_Error via get_term(), but if the taxonomy exists but the term doesn't, then a null value is returned.

For get_cat_name(), I think you should be expecting either a name or nothing.

The larger fix I mentioned above doesn't seem to be needed here -- all we need to do is patch get_cat_name(), apparently.

[nacin]

I chose null here, but false or an empty string might make more sense.

[miqrogroove]

Tested using the original test case on 2.9.1. Works much better so far.

[filosofo]

I think it should be an empty string returned since this function is used in themes.

[miqrogroove]

echo NULL; doesn't cause problems generally, but I agree it would look better to patch without changing the documented return type.

[nacin]

Yea, I agree. I had been thinking about this for a bit now. An empty string makes much more sense.

[nacin]

Empty string makes far more sense

[miqrogroove]

Re-tested 11737.2.diff on 2.9.1 and working perfectly.

[westi]

Looks good to me.

[nacin]

(In [13074]) Fix notice in get_cat_name(). Return empty string if category does not exist, fixes #11737.