better taxonomy query URL syntax

[misterbisson]

Problem: WP's native taxonomy URL syntax supports logical OR/IN and AND operations, but not NOT IN. Blog post with more rambling: ​http://maisonbisson.com/blog/post/16074/better-taxonomy-query-syntax/ .

Solution: the attached patch extends the URL syntax to support these logical operators.

• Taxonomy terms are separated by commas (it preserves support for the old +separated syntax).

• Terms prepended with a + are required (AND)

• Terms prepended with a - are excluded (NOT IN)

• All other terms are simply IN

Examples:

• ​http://site.org/tag/term-one,term-two/ : posts containing one or more of the named terms

• ​http://site.org/tag/+term-one,+term-two/ : posts containing both of the named terms

• ​http://site.org/tag/term-one,-term-two/ : posts containing term-one, but excluding term-two

Working examples (at least until I revert my site):

• ​http://maisonbisson.com/blog/post/tag/wordpress,+mysql/ : IN and AND syntax (it's an accident of how the query is handled internally that it doesn't require a + to be AND'd in this case)

• ​http://maisonbisson.com/blog/post/tag/wordpress+mysql/ : old-style AND syntax

• ​http://maisonbisson.com/blog/post/tag/wordpress,mysql/ : IN syntax

• ​http://maisonbisson.com/blog/post/tag/wordpress,-mysql/ : NOT IN syntax for the second term

• ​http://maisonbisson.com/blog/post/tag/-wordpress,+mysql/ : NOT IN the first term, AND the second term

About the patch:

The patch disables the special handling of tags. This is just to narrow the scope of work necessary to demonstrate a working patch.

[vhauri]

+1 for this patch and the functionality it adds.

[wonderboymusic]

Not quite sure that's "better" - the URL isn't the greatest place to introduce logical AND as + - this seems to only make sense if you are using your URL as a user input for searching. Filtering pre_get_posts to alter tax_query and do a custom intersection is the suggested approach here.