[wp-hackers] Best practice way for a plugin to use WP_Rewrite

[Matt Jacob]

Hi everyone,

I've searched long and hard for a definitive answer to this question,
but I came across a lot of misinformation and bad advice along the
way. Basically, all I want to do is add a few known (not dynamic) URIs
to WordPress via a plugin---with pretty permalinks if they're enabled
and standard query string variables if they're not.

What I've got so far works perfectly fine, except in a couple edge
cases. I've got this function that's called on plugin activation and
when someone saves the plugin's options page:

    private function DeployRewriteRules() {
        global $wp_rewrite;

        add_filter('rewrite_rules_array', array($this, 'InsertRewriteRules'));
        $wp_rewrite->flush_rules();
    }

    public function InsertRewriteRules($rules) {
        $new_rules = array(
            'pingfm/post/([a-zA-Z0-9]{32})/?$' =>
'index.php?pa=post&pk=$matches[1]',
            'pingfm/status/([0-9]+)/?$'        =>
'index.php?pa=status&pi=$matches[1]',
            'pingfm/feed/?$'                   => 'index.php?pa=feed',
        );

        return $new_rules + $rules;
    }

Unfortunately, sometimes other things modify the rewrite rules, and
then my users have to deactivate/reactivate or save the plugin
settings page again in order to get mine back.

As of 2.8, I know I can hook into the "permalink_structure_changed"
action, and this gets me about 90% of the way there. The edge case I
mentioned earlier is when someone hits the save button on the
Permalink Settings page without actually changing anything. The new
rules are saved out, but the action is skipped over.

I *could* call my DeployRewriteRules() function on every page load,
but I know that flushing the rewrite rules is pretty
resource-intensive, and that's not acceptable to my users.

And that leaves me with this: what is the best practice method for
ensuring that my rewrite rules are present at every page load? Is
there one, or are there just varying degrees of bad methods? Would it
be feasible to add a "permalink_structure_saved" hook in a future
release?

Thanks!

Matt