Canonical redirections not suited for Queries with multiple query vars and "pretty permalinks" in general

[dd32]

When the Canonical code was originally written, it served it's purpose quite well. However, over the years the number of Query vars which can be used to access content via has increased, and so have the number of archive views. This has lead to increased complexity in the Taxonomy canonical code which has needlessly caused bugs.

What I'm proposing, is that it might be time to lay to rest the current if.. elseif.. elseif.. style checks, It's not possible for 1 if branch to handle every single access point without duplicating another branch.

As a result, I've put a half-finished together alternate version of Canonical, It's based on tallying up which query vars have been used/accounted for and removing any duplicates.. It's certainly not the best, but it's fairing better with the unit tests so far.

Unit Testing: http://unit-tests.trac.wordpress.org/browser/wp-testcase/test_includes_canonical.php
Before: FF.......FFFF..FFF.....F......FFFFFF.F....F.....FF....FF...
 After: FF...........FFF..................FF..................F....

It's a work in progress, but it's worth considering IMO.

Attaching a diff, and the full file (since the diff is going to be rather unreadable in some sections)

[dd32]

The approach taken in that alteration is to continue using the if branching, but taking note of what query parameters which can be removed with that url(ie. which ones the Path part of the url will take care of - the Rewrite), and ensuring that only those are removed, retaining all other params via $_GET.

It has a few failings still, and a few regressions (can't handle custom rewrite rules at all in it's present form) and is a rather hack job..