Term intersection requests ignore non-existent terms.

[ryan]

Perform a term intersection such as tag=foo+bar. If foo doesn't exist then bar is queried solo, thus reducing the request to tag=bar. Intersections that include terms that do not exist should not return any terms.

I thought I fixed this. Obviously not.

It was fixed for unions. Intersections seem to have slipped through.

Sort of related: #17199

I ended up using exceptions, since otherwise I would have to check for an error after each call to tranform_query(). I'm not a big fan of exception handling, but in self-contained cases like this, they come in handy.

We should stick to WP_Error usage. No need to introduce an exception here.

As I said, the point of using exceptions here is to avoid error checking at each step. You can't do that with WP_Error message.

Replying to scribu:

As I said, the point of using exceptions here is to avoid error checking at each step. You can't do that with WP_Error, unless it's made throwable.

Yes. But using WP_Error and checking for it makes the code flow explicit and more readable and it how WordPress works.

17194.2.diff​ uses WP_Error.

Use WP_Error instead of exceptions

(In [17686]) Handle term intersection requests containg inexistent terms. Props scribu. fixes #17194