Duplicate term insertion allowed after insertion with case differences

[jazbek]

I've discovered a case where duplicate terms can be inserted with wp_insert_term(). Steps to reproduce:

1. Insert a term, i.e.

    wp_insert_term('USA', 'country');
   

2. Insert the same term, but with a different case, i.e.

    wp_insert_term('usa', 'country'); // it's ok that this succeeds, because technically it *is* different (case-wise)
   

3. Insert the same term as in step 2. It should fail, but doesn't:

    wp_insert_term('usa', 'country'); // succeeds
   

This is because wp_insert_term() does the following:

1. Finds the first term in the db that matches the initial (non-unique) slug for the new term name
2. If the name of the found term doesn't match the new term name, then insert continues. In the example above, it's comparing all subsequent 'usa' term names to the first 'USA' term name and determining that it's ok to continue, when it's not because there are other 'usa' terms that it didn't look at.

Check the term name, not slug, use LIKE BINARY

Is there a reason duplicate term checking in wp_insert_term() uses the slug instead of the name?

Replying to kurtpayne:

Is there a reason duplicate term checking in wp_insert_term() uses the slug instead of the name?

Probably because you can't have duplicate slugs, but I'd expect there to also be a check for the name. I'm guessing there are probably back-compat concerns for people who have existing terms of both cases and that's why it's still allowed.

Replying to DrewAPicture:

Probably because you can't have duplicate slugs

It looks like a unique slug is already picked via:

$slug = wp_unique_term_slug($slug, (object) $args);