[wp-trac] [WordPress Trac] #49220: rel_canonical generates the wrong canonical structure for paginated pages.

[WordPress Trac]

#49220: rel_canonical generates the wrong canonical structure for paginated pages.
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 Reporter:  bradleyt      |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  Canonical     |     Version:  4.6
 Severity:  normal        |  Resolution:
 Keywords:  close         |     Focuses:
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Comment (by bradleyt):

 Hi @SergeyBiryukov,

 Sorry for the delaying in following up on your reply - I have been trying
 to check that my thinking is correct in regards to this issue. Firstly,
 let me say that this bug can be reproduced on a fresh install of
 WordPress. That said, there are a few conditions for this bug to be
 reproducible, which I didn't initially realise:

  - The `page_on_front` setting needs to be set to a static page. I.e. this
 issue does not seem to affect sites where the homepage is an archive.
  - Pretty permalinks must be enabled
  - The bug is only reproducible on the site homepage.

 To give some examples of what that means in practice:

  - wordpress.org/page/2/ has the wrong canonical because it is the
 homepage for wordpress.org
  - wordpress.org/showcase/page/2/ has the wrong canonical because the
 showcase pages are actually setup as a standalone WordPress site (as part
 of a multisite installation)
  - wordpress.org/showcase/submit-a-wordpress-site/page/2/ is not affected,
 because it is not the homepage.
  - wordpress.org/news/ is not affected because although it is the homepage
 of a news site (like the showcase setup) the homepage is not set to show a
 static page.

 *Note that I am using the term `homepage` to refer to the page served at a
 site's root URL, regardless of the setup of that site.

 `wp_get_canonical_url` calls `get_query_var( 'page', 0 )`. Normally when
 visiting a URL of the style wordpress.local/another-page/page/2/ this
 returns 0. However, on an incorrectly paginated homepage such as
 wordpress.local/page/2/ this returns the page number - note that calling
 `get_query_var( 'paged', 0 )` would also (correctly) return the same page
 number.

 It seems that the incorrect `page` query variable is originating from
 `WP_Query->parse_query` specifically from an area commented as "Correct
 is_* for page_on_front and page_for_posts".

 I have not got as far as being able to suggest a solution, but for now I
 hope that we can move away from the idea that this is related to the
 wordpress.org setup and focus on finding a solution. I personally believe
 that there are significant backwards-compatibility blockers to #28081
 being resolved any time soon, and so I am in favour of this
 `wp_get_canonical_url` bug being treated as a standalone issue.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/49220#comment:4>
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