Die fast in get_posts if get_user_by returns false

[david.binda]

In case a username in the URL or passed to WP_Query via any other way is invalid - such a user is not in database - the code currently casts the false value returned from get_user_by to 0 via absint - see https://core.trac.wordpress.org/browser/trunk/src/wp-includes/class-wp-query.php#L2126

Instead of trying to query unassigned posts (with post_author equal to 0) for all invalid usernames, the query should die fast and return no posts.

[SirLouen]

Replying to david.binda:

Instead of trying to query unassigned posts (with post_author equal to 0) for all invalid usernames, the query should die fast and return no posts.

Why not short-circuiting fast and furiously?
Unit tests are too focused on that strange SQL condition of 1==0. I think can be simpler, just ignoring those two assertNotRegExp and good to go.

I've added a patch with this.

If you like, you can integrate changes in a GitHub PR (both short-circuit and changes in Unit-Tests), and we could try to move this forward. It's a very niche case, but it's true that we save at least, one query to the DB. It's a little performance gain.