[wp-trac] [WordPress Trac] #29615: Hierarchical Post Type 'Default' Permalinks

[WordPress Trac]

#29615: Hierarchical Post Type 'Default' Permalinks
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 Reporter:  loushou       |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Permalinks    |    Version:  4.0
 Severity:  normal        |   Keywords:
  Focuses:                |
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 '''Intro'''

 I recently helped release a plugin that I have worked on for a while now.
 Until now, every environment that has used this plugin has been using
 'non-default' permalinks, usually something involving %postname%.
 Yesterday I as doing some testing on a clean, unmodified install of
 WordPress and found that my post permalinks are not working. After some
 short investigation this morning I found out why, which I will explain in
 a second. Also, I did some checking on my various legacy dev environments
 and have found that this problem has been around since at least 3.2.1.
 Here is a detailed explanation of the problem and it's roots:

 '''My Setup(s)'''

 I have verified that this problem exists in as early as version 3.2.1 and
 as late as version 4.0 (official release). My dev environments span the
 gamut between those versions, and this problem exists in all of them.

 '''Description'''

 The basic problem boils down to one key issue: there is a mismatch in
 permalink generation and permalink interpretation for 'non-page'
 hierarchical post types, when using 'default permalinks'
 (http://example.com/?p=123).

 For 'non-page' hierarchical post types, when we generate the permalink for
 the post, while the 'default permalinks' are selected, we use this format:
 http://example.com/?post_type=pagename , where 'post_type' is the 'slug
 name' of the post type itself, and 'pagename' is equal to
 '$post->post_name'. Nothing seems wrong with this until you look at how
 the permalink is interpreted by WP_Query. In WP_Query, when looking up a
 'non-page' hierarchical post type, we use the 'get_page_by_path()'
 function to determine the post_id. This function expects that the pagename
 be something like http://example.com/?my_post_type=parent-post/child-post.
 In the current format of the permalink (http://example.com/?my_post_type
 =child-post), that function tries to find a 'parent post' (post_parent =
 0) that is named 'child-post', and thus fails, returning 0 as the post_id.

 '''Reproduction Steps'''

 - Freshly install any version of WordPress 3.2.1 or later.
 - Verify that 'Default' is selected as the permalink structure on
 'Settings -> Permalinks'
 - Create a hierarchical post type
 - Create a parent post of that post type
 - Create a child post of that parent post, of that same post type
 - Click the 'view post' link in the edit post page of the child post (or
 browse to it some other way)
 - Observe a 404 error

 '''Expectations'''

 First, this is only a problem when there is a 'non-page' hierarchical post
 type and default permalinks, which by definition means that it is only a
 problem when a plugin or theme is active. None-the-less it is a problem.

 Second, when clicking the admin 'view post' link, we should be able to
 view the post. This logic flaw prevents that in all cases.

 Lastly, the get_permalink function (more specifically the
 get_post_permalink() function) should return a permalink that can be
 interpreted by WP_Query, no matter what permalink structure is used.

 '''Additional Information'''

 Based on some research, it seems that this whole problem could be solved
 by moving one of the if statements in the get_post_permalink() up a couple
 ranges, so that it affects both halves of the primary if statement. To be
 clearer, in version 4.0, move wp-includes/link-template.php at 262-263 above
 line wp-includes/link-template.php at 260.

 If this is done, then the else statement on wp-includes/link-
 template.php at 267 will also have a hierarchical value for $slug, and thus
 will produce proper permalinks. I have tested it any it will still produce
 valid non-hierarchical permalinks with this code also.

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Ticket URL: <https://core.trac.wordpress.org/ticket/29615>
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