In get_terms(), getting a fatal error iterating on $terms inside get_terms filter.

[JustinSainton]

Our plugin (WP eCommerce) has a filter on get_terms for some custom sorting.

In WP 4.5.2, ​this code works fine. In trunk, it is broken.

After ​chatting a bit with @boone, our best guess is that the move to WP_Term_Query moved the filtering of get_terms() so that counts are now filtered, and before, they likely were not.

To be clear - the fault is in our code (we should have assumed possible return types of int, WP_Error, or an array), but there is a clear change in core.

For us, the intermediate solution is to simply add an is_array() check and return early. For core, it may be worth ensuring that the values are only filtered in the same places that they were in previous versions of WordPress.

[JustinSainton]

Update: Confirmed @boonebgorges' suspicion: ​https://github.com/WordPress/WordPress/blob/4.5.2/wp-includes/taxonomy.php#L1640-L1642

Also, existing code ​has an unused remnant variable.

[boonebgorges]

In 37622:

Remove unused variable from get_terms().

Missed in [37572]. See #35381.

Props JustinSainton.
See #36992.

[boonebgorges]

In 37623:

Taxonomy: Don't pass results of 'count' query through 'get_terms' filter.

Use of the 'get_terms' filter was consolidated in [37572], with the
introduction of WP_Term_Query. At that time, the result of 'count=true'
queries began being filtered by 'get_terms'. This breaks existing 'get_terms'
callbacks, which often assume that the returned value will be an array or a
WP_Error object.

Props JustinSainton.
Fixes #36992.

[nathanrice]

FWIW, this is still somewhat broken. I've not had a chance to chase down why, but if you use array type hinting in your callback on the get_terms filter, you get the following error.

Catchable fatal error: Argument 1 passed to genesis_get_terms_filter() must be of the type array, string given

Obviously, this is in the Genesis theme.

Anybody know what's going on here? Why is a argument not of type array ever being passed to the get_terms filter?

[boonebgorges]

Replying to nathanrice:

FWIW, this is still somewhat broken. I've not had a chance to chase down why, but if you use array type hinting in your callback on the get_terms filter, you get the following error.

Catchable fatal error: Argument 1 passed to genesis_get_terms_filter() must be of the type array, string given

Obviously, this is in the Genesis theme.

Anybody know what's going on here? Why is a argument not of type array ever being passed to the get_terms filter?

I just looked through again. At a glance, I don't see anywhere where something other than an array might be passed through the filter. It would be helpful if you could generate a full stack trace, including (a) the args being passed to get_terms() and WP_Term_Query, and (b) the non-array value that's being erroneously passed to the filter (is it a WP_Error? a boolean? or something else?)

[nathanrice]

This was sent by one of our testers. I can also send a copy of Genesis to you if you want to see any of this for yourself.

[03-Jun-2016 12:05:56 UTC] PHP Fatal error:  Uncaught TypeError: Argument 1 passed to
genesis_get_terms_filter() must be of the type array, string given, called in 
/Users/nickcernis/www/trunk/wp-includes/plugin.php on line 235 and defined in 
/Users/nickcernis/www/trunk/wp-content/themes/genesis/lib/admin/term-meta.php:268
Stack trace:
#0 /Users/nickcernis/www/trunk/wp-includes/plugin.php(235): genesis_get_terms_filter('2', Array)
#1 /Users/nickcernis/www/trunk/wp-includes/taxonomy.php(1227): apply_filters('get_terms', '2', Array, Array, Object(WP_Term_Query))
#2 /Users/nickcernis/www/trunk/wp-includes/taxonomy.php(1694): get_terms(Array, Array)
#3 /Users/nickcernis/www/trunk/wp-admin/includes/class-wp-terms-list-table.php(127): wp_count_terms('category', Array)
#4 /Users/nickcernis/www/trunk/wp-admin/edit-tags.php(212): WP_Terms_List_Table->prepare_items()
#5 {main}
  thrown in /Users/nickcernis/www/trunk/wp-content/themes/genesis/lib/admin/term-meta.php on line 268

[boonebgorges]

Thanks, @nathanrice. I see now that there was an error in [37623], which I'll fix now.

[boonebgorges]

In 37634:

Taxonomy: No, really, don't pass results of 'count' query through 'get_terms' filter.

[37623] used the wrong parameter name (count=true instead of fields=count).

For greater flexibility and forward compatibility with other potential changes
to the return value of get_terms(), we now do a looser check: any non-array
value is excluded from the filter.

Fixes #36992.