In my latest app I wanted to force the naming of WooCommerce Product Attributes as my code would cycle through them to decide which custom properties apply to Variable Products.  A great way to introduce structure for custom values for variable Products.

My problem was that I grew the attribute names to include embedded information so that I could determine if the custom field was text or numeric, if it was to be displayed in the custom form or not, etc.  My attribute names grew long quite quick.  I should have kept an eye on that.

While experimenting with the code I accidentally got into a bit of a loop and ended up trying to register attribute slugs longer than 32 characters.  This threw an error but I’ve got myself stuck.

When I browse to any page of the site I get the error

Notice: register_taxonomy was called incorrectly. Taxonomy names must be between 1 and 32 characters in length. 
Please see Debugging in WordPress for more information. 
(This message was added in version 4.2.0.) in /Users/tony/Local Sites/nooksii/app/public/wp-includes/functions.php on line 5167

The site became unusable.

I commented out my code that tries to check and create missing attributes but the problem persisted.
I assumed that the setting was in the database and was trying to be re-set on INIT. So I cleared the table wp_woocommerce_attribute_taxonomies. I also cleared down the sessions table wp_woocommerce_sessions.
And rebooted the server.
But the problem persists. With debug running I can see the attribute causing the problem:

function register_taxonomy( $taxonomy, $object_type, $args = array() ) {
.
.
// in here the passed variable $taxonomy has the value 'pa_pa_pick-txt-clear-item-part-ref'
.
}

34 characters – clearly too long. But where is it cropping up from? My code is NOT trying to do any new registrations.

Here is the call stack:-

Clearly MY code has not been touched. All WP init code.
So, where is WP getting the values to make a registration from?

A quick search of the WP tables shows similar values (but not exact ones like the one causing my problem) in wp_options in the column option_name under entry _transient_wc_attribute_taxonomies.

As I’m on a dev system and I’ve spent a lot of time already I’m going to delete all the values in _transient_wc_attribute_taxonomies and see if I can get sorted.

Guess what? That pushed a new error into wc-attribute-funciton.php. Line 73 (in my case) the WC code is trying to do an array_filter to return into $raw_attribute_taxonomies but the error says the passed in parameter is NOT an array.

This is backed up with the line in that function:

$raw_attribute_taxonomies = get_transient( 'wc_attribute_taxonomies' );

I also noticed the code:

if ( false === $raw_attribute_taxonomies ) {
  global $wpdb;
  $raw_attribute_taxonomies = $wpdb->get_results( "SELECT * FROM {$wpdb->prefix}woocommerce_attribute_taxonomies WHERE attribute_name != '' ORDER BY attribute_name ASC;" );
   .
   .

So I’ve basically screwed something up by emptying those tables and entries.

I’m guessing there is a link to the wp_term_taxonomy table (I recognised some of the transient values I deleted) so I need to delete my custom attribute names from there (yes – even the ones that did not cause a problem).

Now I’m in a bit of a mess I’m considering deleting everything (delete the site) and re-install a fresh WooCommerce base site.

A search for “woocommerce repair database” did not reveal any solutions. No specific hits at all.

In conclusion I’m putting this post out as a warning. Try not to get into this mess in the first place.
If you have code that registers Product Attributes make sure you do the following:-

• Check the length of the attribute slug.
• Check you are not using reserved slug values: wc_check_if_attribute_name_is_reserved

I would have loved to investigate this issue.  I suppose it could be reproduced by forcing a large attribute name and seeing if the system gets itself stuck again.  That an exercise for another day.