[wp-trac] [WordPress Trac] #61761: `wp_term_insert` inconsistent validation logic for `name` and `slug`

[WordPress Trac]

#61761: `wp_term_insert` inconsistent validation logic for `name` and `slug`
----------------------------+-----------------------------
 Reporter:  xipasduarte     |      Owner:  (none)
     Type:  enhancement     |     Status:  new
 Priority:  normal          |  Milestone:  Awaiting Review
Component:  General         |    Version:
 Severity:  normal          |   Keywords:
  Focuses:  administration  |
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 Right now the way a term is inserted is inconsistent with cases that
 render the same `($name, $slug)` pair as either an error or a success.

 **Considerations**
 Inferred from the code logic:
 - The `$name` is treated as a sort of logically enforced primary key
 - The `$slug` is enforced as unique

 **Inconsistencies**
 The following examples are only indicated as `($name, $slug)` pairs for
 simplicity, but they represent `wp_insert_term` operations.


 {{{
 ('A', 'a') // Success
 ('A', null) // Error: term name exists
 ('A', 'a') // Success (term slug is changed to "a-2")
 }}}

 Exploring a little more on the second insert we can have the following.


 {{{
 ('A', 'b') // Success
 ('A', null) // Error: term name exists
 ('A', 'a') // Success (no term slug change)
 }}}


 **Documentation**
 In the documentation it is stated that:

 > If the term already exists on the same hierarchical level, or the term
 slug and name are not unique, a `WP_Error` object will be returned.

 The documentation is not clear on what "exists" means in the context of
 hierarchical terms, but it indicates that the pair `($name, $slug)` should
 be the logically enforced primary key. If this is the case, which is not
 apparent from the code, than the same issues apply, although a different
 solution is required.

 **Proposal**
 Considering what a term is, a relationship (see
 https://wordpress.org/documentation/article/taxonomies/):
 1. always return `WP_Error( 'duplicate name' )` when the `$name` is a
 duplicate (inside the same hierarchical level), preventing duplicate
 visual references. (__Example:__ A term "Vegetarian" with `$slug =
 'vegetarian'` would be indistinguishable from another "Vegetarian" with
 `$slug = 'vegetarian-2'`.)
 2. make the `('A', null)` examples behave as `('A', 'a')`.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/61761>
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