Wrong canonical link on wp-admin pages

Question

I have a subdomain:

https://blog.example.com/

I forcibly redirects to directory:

https://www.example.com/blog

By changing site URL and some RewriteRule on .htaccess.

My .htaccess:

    <IfModule mod_rewrite.c>
    RewriteEngine On

    RewriteBase /blog/
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . /blog/index.php [L]

    RewriteCond %{HTTP:X-Forwarded-Host}i ^example\.com
    RewriteCond %{HTTP_HOST} ^blog\.example\.com$
    RewriteRule ^/?(.*)$ https://www.example.com/blog/$1 [L,R=301,NC]

    RewriteCond %{HTTP:X-Forwarded-Proto} !https
    RewriteCond %{HTTPS} off
    RewriteRule ^/?(.*)$ https://www.example.com/blog/$1 [L,R=301,NC]
    </IfModule>

My wordpress address and site address are:

WordPress Address (URL): /blog

Site Address (URL): https://www.example.com/blog

Now the website working fine, but I found an error in wp-admin canonical url on all admin pages:

Uncaught SecurityError: Failed to execute 'replaceState' on 'History': A history state object with URL 'blog.example.com/wp-admin/index.php'; cannot be created in a document with origin 'example.com'; and URL 'example.com/blog/wp-admin/index.php';

When I dig more I found the canonical link is still subdomain( blog.example.com ) :

<link id="wp-admin-canonical" rel="canonical" href="http://blog.example.com/wp-admin" />
    <script>
        if ( window.history.replaceState ) {
            window.history.replaceState( null, null, document.getElementById( 'wp-admin-canonical' ).href + window.location.hash );
        }
    </script>

Is there any solution for changing this canonical url from https://blog.example.com to https://www.example.com/blog

Answer 1

wp-admin-canonical is broken, as it assumes how WordPress is installed.

there was a plugin to fix it, but the plugin was removed from the plugin repository apparently. It is still on github and pluginmirror though: https://github.com/wp-plugins/remove-wp-canonical-url-admin-hack http://www.pluginmirror.com/plugins/remove-wp-canonical-url-admin-hack/

Answer 2

Update

The code below didn't really worked for me, as it adds a correct canonical tag but I wasn't able to remove the wrong one with remove_action.

Also, I found that pagination and sorting links in post and page lists had the wrong URL on it as well.

So the solution has been much simpler, just add $_SERVER['HTTP_HOST'] = 'www.yoursite.com'; anywhere in wp-config.php.

---

Previous answer

I've overrided the wp-admin-canonical by adding this hooks in functions.php:

remove_action( 'admin_head', 'wp_admin_canonical_url' );
add_action( 'admin_head', 'wp_set_admin_canonical_url' );

function wp_set_admin_canonical_url() {
    $removable_query_args = wp_removable_query_args();

    if ( empty( $removable_query_args ) ) {
        return;
    }

    // Ensure we're using an absolute URL.
    $current_url  = admin_url( preg_replace( '#^[^?]*/wp-admin/#i', '', $_SERVER['REQUEST_URI'] ) );
    $filtered_url = remove_query_arg( $removable_query_args, $current_url );
    ?>
    <link id="wp-admin-canonical" rel="canonical" href="<?php echo esc_url( $filtered_url ); ?>" />
    <script>
        if ( window.history.replaceState ) {
            window.history.replaceState( null, null, document.getElementById( 'wp-admin-canonical' ).href + window.location.hash );
        }
    </script>
    <?php
}

I've taken the code from this pull request: https://github.com/WordPress/wordpress-develop/pull/1504