tag_id Doesn't Work in WP_Query

[miqrogroove]

WP_Query::parse_query() stores a value in $qv['tag_id'] but it does not query the tag name, and WP_Query::get_posts() never checks the tag_id value. Thus, this variable does nothing.

I noticed this while working on #10640. The tag_id variable could be useful for the specific purpose of URL shortening where long tag slugs may be problematic (e.g. micro-blogging).

[miqrogroove]

Leaving as "defect" because parse_query() is accepting a parameter that does not work.

Adding, however, that the lack of tag_id support in get_posts() appears to be by design and is not a bug in itself. Since the HTML class names of tags are like "tag-slug" rather than "tag-item-id", the ID numbers are currently a semi-private reference system. Website guests would have no use for ID queries, except within a plugin feature such as URL shortening.

[miqrogroove]

Also note that any registered user can use edit-tags.php.

[dd32]

I ran accross this today..

Personally I think all references to it should probably just be removed, Unless it was implemented at some point in time.

I can see the usefulness of having access to the ID, but on MS sites that can change. The slug is a better source of reliable data. (Of course, the slug can be modified too tho).

[miqrogroove]

On MS sites the tag ID can change? Is it different from the way post IDs and category IDs work?

[dd32]

Its not just Category ID's that change, Its Term ID's on all taxonomies. Whilst a single blog can always be assured to retain the same term ID, If another blog modifies the term, They recieve a new Term_id with their modifications, thats so they dont clobber one another's term details.

Its not like posts which are one after the other on a single blog, Terms can be shared accross blogs with MS.

[miqrogroove]

Punting per IRC meetup. See also #12589.

[filosofo]

I'm closing as a duplicate of #14166, as that has a patch.