[wp-trac] [WordPress Trac] #43517: Adding support of default category term for custom taxonomies

[WordPress Trac]

#43517: Adding support of default category term for custom taxonomies
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 Reporter:  enrico.sorcinelli       |       Owner:  whyisjake
     Type:  defect (bug)            |      Status:  closed
 Priority:  normal                  |   Milestone:  5.5
Component:  Taxonomy                |     Version:
 Severity:  normal                  |  Resolution:  fixed
 Keywords:  has-patch has-dev-note  |     Focuses:
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Comment (by johnjamesjacoby):

 A bit of feedback about this feature, now that I've implemented it into a
 plugin I help maintain.

 Coupling the `'default_term'` WP_Taxonomy argument with a registered
 setting (for storing the ID of the default term) puts developers into a
 catch 22 situation.

 The setting stores a term ID, but the argument requires a term Name. 🤔

 So you don't want to register the taxonomy without `default_term` (because
 you want all the admin-area UI goodies that come with that argument being
 non-empty) but you can't get the default-term name from the database
 without a call to `get_term()` which works best when it's supplied a
 taxonomy, which isn't registered yet. 🔁

 It means an early `get_term()` call that may potentially have legacy
 issues with shared terms even before the call to `register_taxonomy()`
 happens to register the taxonomy being queried for via `get_term()`. 🔁

 {{{
 // Default arguments
 $args = array();

 // Default term
 $default = get_option( 'default_term_taxonomy_name' );

 // Default exists
 if ( ! empty( $default ) ) {

         // Get term (does not use taxonomy, because it's not registered
 yet)
         $term = get_term( $default );

         // Term exists
         if ( ! empty( $term->name ) ) {
                 $args['default_term'] = array( 'name' => $term->name );
         }
 }

 // Register
 register_taxonomy(
         'taxonomy_name',
         'post_type,
         $args
 );
 }}}

 This above code and approach will work reliably for sites that do not have
 shared terms, but has a small potential to not work correctly on sites
 that are sharing terms across taxonomies.

 It also was quite weird to implement. I had hoped the `default_term`
 argument would accept the numeric ID of the value straight from the
 registered setting, handling verification & fallback internally. I
 understand why that isn't how it works, but it also doesn't seem super
 great to pass that burden down to each plugin that uses it.

 I'm glad to see this feature exist and working how it does in WordPress
 admin, and hope to see further improvements to it. 🙏

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/43517#comment:43>
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