Rewriting a date hierarchy into a 'yyyy-mm-dd' slug

Question

I am building a magazine website with an issue custom post type. The slugs for each issue follow the format YYYY-MM-DD according to the issue's publish date. Currently the permalinks are set up as http://host/magazine/2014-06-08 but I would like them to be accessed through the URL http://host/magazine/2014/06/08.

Here is what I'm currently doing in my functions.php:

$issue_structure = '/magazine/%issue%';
$wp_rewrite->add_rewrite_tag("%issue%", '(\d{4}-\d{2}-\d{2})', "issue=");
$wp_rewrite->add_permastruct('issue', $issue_structure, false);

I tried adding this to my .htaccess file:
RewriteRule ^magazine/(\d{4})/(\d{2})/(\d{2}) /magazine/$1-$2-$3 [QSA,L]

And I also tried added this to my WP_Rewrite rules:
add_rewrite_rule('magazine/(\d{4})/(\d{2})/(\d{2})', 'magazine/$matches[1]-$matches[2]-$matches[3]', 'top');

Neither of those approaches have worked, either separately or in combination. And I was careful to flush my rewrite rules. In fact, there's no evidence of that add_rewrite_rule call in my Rewrite Rules Inspector list, so I suspect I'm not using it correctly.

Another (hacky) thing I tried was manually tweaking the post_name field in the database to be 2014/06/08 and switching up the rewrite tag to be $wp_rewrite->add_rewrite_tag("%issue%", '(\d{4}/\d{2}/\d{2})', "issue="); but that didn't work either.

What else should I try?

Answer 1

Internal rewrite rules have to point to index.php and set the proper query vars for WordPress to be able to load the requested object:

add_rewrite_rule(
    'magazine/(\d{4})/(\d{2})/(\d{2})/?',
    'index.php?issue=$matches[1]-$matches[2]-$matches[3]',
    'top'
);

That should get incoming requests to resolve correctly, however, that's only half the task. If you call the_permalink for your posts, you'll still get the format you defined when you registered your post type. To fix that you have to filter post_type_link to output the URLs in the correct format.