Conflicting rewrite rules breaking single posts

Hello Pascal,

The bug you are experiencing is curious. The faulty rewrite rule is explicitly removed by this line: https://github.com/polylang/polylang/blob/3.5.2/include/links-directory.php#L181. I can reproduce by commenting it.
So it looks like rewrite rules are computed while this line hasn’t been executed. It’s hooked to wp_loaded with priority 9 (as late as possible just before WP computes rewrite rules).
If it’s not executed, then I guess that the lines after re not executed too and that no rewrite rules are modified to add the language code. Am I right?

Some context that may help:
– We had to change the way we initiate our rewrite rules filters due to https://core.trac.www.ads-software.com/ticket/58998. This was done in https://github.com/polylang/polylang/pull/1345 included in Polylang 3.5. Other PRs were necessary in 3.5.1 and 3.5.2 to fix bugs that we introduced for multisites.
– When saving Polylang settings, the rewrite rules are not flushed the classic way. We delete the option and let the next page loaded compute the rewrite rules. See https://github.com/polylang/polylang/blob/3.5.2/settings/settings-module.php#L255-L257. Up to now this has never caused any issue but this is a difference compared to the simple visit to Settings > Permalinks.

I suppose that there is some conflict. Maybe you can find out which process is executed after you save the settings.

Hello there, as a developer as well I didn’t dig deep into this issue so I’m sorry for rather vague description. Anyway after recent upgrade of WordPress to 6.4 I experience similar issue:

• Single post shows homepage although single.php is present
• URL /admin/ shows homepage as well

For me flushing permalinks doesn’t work (tried by changing permalinks to different settings, saving, changing back, saving).

Saving Polylang settings (event without a change) works.

I do have the exact some problem with all my installations.
As @jirsbek mentioned: Saving the polylang settings fixes the problem, whenever updating the permalinks again the problem is back.

Thanks for the pointers @chouby! That’s already very helpful.

I doubt it’s related to #58998 or WordPress 6.4, because the first time I noticed this issue was in May or so. At first I thought it’s because I started using a block theme, but I’ll dig deeper.

@jirsbek @valentinalisch very interesting! Especially since for you it’s the other way around with saving the settings, plus it sounds related to 6.4 in your case. Might be worth opening a separate topic to debug that one.

Quick update, I think I found the culprit! I found out that the PWA plugin adds some rewrite rules in a way that breaks Polylang’s logic. Here’s the relevant code: https://github.com/GoogleChromeLabs/pwa-wp/blob/62961cdddd24c3aa5d49fc39a219a92d085f8f59/wp-includes/class-wp.php#L9-L33

Happy to report this on the PWA repo if you think this is a bug there.

Interesting, I’m not using this plugin anywhere ??

@swissspidy Indeed, I believe there is some issue with this line: https://github.com/GoogleChromeLabs/pwa-wp/blob/62961cdddd24c3aa5d49fc39a219a92d085f8f59/wp-includes/class-wp.php#L17

I don’t know if you remember the documentation of flush_rewrite_rules() at the time of the codex. It used to tell not to call the function in a function hooked to init, because it is an expensive operation. In fact it was also a source of conflicts that was fixed by https://core.trac.www.ads-software.com/ticket/37892.

A direct call to $wp_rewrite->wp_rewrite_rules() is equivalent to a call to flush_rewrite_rules() from performance point of view. So this is a mistake to call this method on all page loads.

Now the conflict is due to the rewrite rules being evaluated 2 times in the same page load. The first time by this line in PWA, not filtered by Polylang, the second time when the rules are saved to the DB, correctly filtered by Polylang. Indeed $wp_rewrite->extra_rules_top is not reset, and WordPress keeps it from one evaluation to the other. As a consequence, all taxonomy rules (including the problematic language rules that we aim to remove) are not filtered correctly.

I am not sure why the lines https://github.com/GoogleChromeLabs/pwa-wp/blob/62961cdddd24c3aa5d49fc39a219a92d085f8f59/wp-includes/class-wp.php#L17-L27 were added as the rules are flushed at plugin activation. I guess it could be for multisite, but in that case, although not a big deal for this plugin, the rules are not removed at plugin deactivation.

However if they are needed, the quick fix would be to call get_option( 'rewrite_rules') instead of $wp_rewrite->wp_rewrite_rules().

Thanks for the detailed analysis, that all makes sense to me!

I’ll mark this as resolved and track this as a bug on the PWA repo.

Thanks again.

Actually, the PWA plugin is calling flush_rewrite_rules() at the admin_init action.

but it‘s adding the rewrite tags on init, and calling the wp_rewrite_rules() method when the option doesn‘t exist flushes the rules too.

Lets’ continue the discussion on GitHub

Hello there ??

@jirsbek?@valentinalisch, have you found something on your side? I’m having a similar behavior but I don’t use the PWA plugin :s !

Kind regards,

Cedric

@cedriccharles What actually helped me was updating the Polylang to the latest version. As my version was “Pro” it was outdated so I extended the license and upgraded to the latest Pro and it helped.

Thank you @jirsbek ! Unfortunately, it doesn’t help me…

I think my issue seems also related to this. My settings:

• The language is set from the directory name in pretty permalinks
• Hide URL language information for default language UNCHECKED

This should be the correct URL: https://www.wroclawguide.com/de/das-beste-fruhstuck-in-breslau/ and here the correct canonical URL is set as well (same as this URL)

However for some reason, Google found them also without /de/:

https://www.wroclawguide.com/das-beste-fruhstuck-in-breslau/

This URL is not leading to a 404 error or redirect to the correct URL, but to sort of blank search page with “nothing found” and then Google takes the canonical URL from that which always points to the main starting page.

When logged in as admin, a redirect happens.

As result, all our pages are getting removed from the index from google and replaced by the main starting page.

In my view, either the redirect should be enabled for non admins and regular users, or the page shown should be a 404 error, or alternatively at least the canonical URL should be removed from these pages…

This is quite critical due to the de-indexing by Google.